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Liu X, Tian S, Guo W, Li H, Pang B, Wu Y. Competing C and N as Reactive Centers for Microsolvated Ambident Nucleophiles CN -(H 2O) n=0-3: A Theoretical Study of E2/S N2 Reactions with CH 3CH 2X (X = Cl, Br, I). J Phys Chem A 2024; 128:4651-4662. [PMID: 38819200 DOI: 10.1021/acs.jpca.4c01226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
As an ambident nucleophile, CN- has both C and N atoms that can act as the reactive center to facilitate substitution reactions. We investigate in detail the potential energy profiles of CN-(H2O)0-3 with CH3CH2X (X = Cl, Br, I) to explore the influence of solvent molecules on competition between the different nucleophilic atoms C and N involving the SN2 and E2 pathways. The energy barrier sequence for the transition states follows C@inv-SN2 < N@inv-SN2 < C@anti-E2 < N@anti-E2. When two different atoms act as nucleophilic atoms, the SN2 reaction is always preferred over the E2 reaction, and this preference increases with microsolvation. For the ambident nucleophiles CN-(H2O)0-3, C as the reactive center always has stronger nucleophilicity and basicity than N acting as the reactive center. Regarding the leaving group, the height of the energy barrier is positively correlated with the acidity of the CH3CH2X substrate for the E2 pathway and with X-heterolysis for the SN2 pathway. Furthermore, we found that in the gas phase, the energy barrier for different leaving group systems decreases gradually in the order Cl > Br > I, while in the SMD solution, the energy barrier and product energy increase slightly in the system from X = Cl to Br; this change may be due to the significantly weakened transition-state interaction for the X = Br system. Our activation strain, quantitative molecular orbital, and charge analyses reveal the physical mechanisms underlying the various computed trends. In addition, we also demonstrate the two points recently proposed by Vermeeren, P. . Chem. Eur. J. 2020, 26, 15538-15548.
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Affiliation(s)
- Xu Liu
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Shiqi Tian
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Wenyu Guo
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Hui Li
- College of Chemistry, Liaoning University, Shenyang 110036, China
| | - Boxue Pang
- Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China
| | - Yang Wu
- College of Chemistry, Liaoning University, Shenyang 110036, China
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2
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Nacsa AB, Tokaji C, Czakó G. High-level analytical potential-energy-surface-based dynamics of the OH - + CH 3CH 2Cl S N2 and E2 reactions in full (24) dimensions. Faraday Discuss 2024. [PMID: 38804112 DOI: 10.1039/d3fd00161j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
We develop a coupled-cluster full-dimensional global potential energy surface (PES) for the OH- + CH3CH2Cl reactive system, using the Robosurfer program package, which automatically samples configurations along PES-based trajectories as well as performs ab initio computations with Molpro and fitting with the monomial symmetrization approach. The analytical PES accurately describes both the bimolecular nucleophilic substitution (SN2) and elimination (E2) channels leading to the Cl- + CH3CH2OH and Cl- + H2O + C2H4 products, respectively, and allows efficient quasi-classical trajectory (QCT) simulations. QCT computations on the new PES provide accurate statistically-converged integral and differential cross sections for the OH- + CH3CH2Cl reaction, revealing the competing dynamics and mechanisms of the SN2 and E2 (anti, syn, β-α transfer) channels as well as various additional pathways leading to induced inversion of the CH3CH2Cl reactant, H-exchange between the reactants, H2O⋯Cl- complex formation, and H2O + CH3CHCl- products via proton abstraction.
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Affiliation(s)
- András B Nacsa
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Csenge Tokaji
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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Wu X, Bickelhaupt FM, Xie J. Solvent-induced dual nucleophiles and the α-effect in the S N2 versus E2 competition. Phys Chem Chem Phys 2024; 26:11320-11330. [PMID: 38536735 PMCID: PMC11022550 DOI: 10.1039/d4cp00671b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 03/14/2024] [Indexed: 04/18/2024]
Abstract
We have quantum chemically investigated how microsolvation affects the various E2 and SN2 pathways, their mutual competition, and the α-effect of the model reaction system HOO-(H2O)n + CH3CH2Cl, at the CCSD(T) level. Interestingly, we identify the dual nature of the α-nucleophile HOO- which, upon solvation, is in equilibrium with HO-. This solvent-induced dual appearance gives rise to a rich network of competing reaction channels. Among both nucleophiles, SN2 is always favored over E2, and this preference increases upon increasing microsolvation. Furthermore, we found a pronounced α-effect, not only for SN2 substitution but also for E2 elimination, i.e., HOO- is more reactive than HO- in both cases. Our activation strain and quantitative molecular orbital analyses reveal the physical mechanisms behind the various computed trends. In particular, we demonstrate that two recently proposed criteria, required for solvent-free nucleophiles to display the α-effect, must also be satisfied by microsolvated HOO-(H2O)n nucleophiles.
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Affiliation(s)
- Xiangyu Wu
- Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China.
| | - F Matthias Bickelhaupt
- Department of Chemistry and Pharmaceutical Sciences, AIMMS, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands.
- Institute for Molecules and Materials (IMM), Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg 2006, South Africa
| | - Jing Xie
- Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China.
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Zhao S, Fu G, Zhen W, Wang H, Yang L, Zhang J. Competitive dynamics of E2 and S N2 reaction driven by collision energy and leaving group. Phys Chem Chem Phys 2023; 25:28086-28093. [PMID: 37817676 DOI: 10.1039/d3cp03832g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
The competition between E2 and SN2 reactions is essential in organic chemistry. In this paper, the reaction mechanism of F- + CH3CH2Cl is investigated utilizing direct dynamics simulations, and unravel how the collision energy (Ecoll) and the leaving group affect the competition between SN2 and E2 in the F- + CH3CH2Y (Y = Cl and Br) reactions. Simulation results for F- + CH3CH2Cl reaction show that the anti-E2 channel is dominant, but with the increase of Ecoll from 0.04 to 1.9 eV the branching ratio of the anti-E2 pathway significantly decreases by 21%, and the SN2 pathway becomes more important. A transition from indirect to direct reaction has been revealed when Ecoll is increased from 0.04 to 1.90 eV. At lower Ecoll, a large ratio of indirect events occurs via a long-lived hydrogen-bonded complex, and as the collision energy is increased, the lifetimes of the hydrogen-bonded complexes are shortened, due to an initial faster relative velocity. The simulation results of F- + CH3CH2Cl are further compared with the F- + CH3CH2Br reaction at Ecoll of 0.04 eV. Changing the leaving group from Cl to Br drastically suppresses the indirect events of anti-E2 with a branching ratio decreasing from 0.46 to 0.36 due to the mass effect, and promotes direct rebound mechanism resulting from a looser transition state geometry caused by varied electronegativity.
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Affiliation(s)
- Siwei Zhao
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Gang Fu
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Wenqing Zhen
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Hongyi Wang
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Li Yang
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Jiaxu Zhang
- State Key Laboratory of Urban Water Resource and Environment, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
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Hansen T, Vermeeren P, Zijderveld KWJ, Bickelhaupt FM, Hamlin TA. S N 2 versus E2 Competition of Cyclic Ethers. Chemistry 2023; 29:e202301308. [PMID: 37338310 DOI: 10.1002/chem.202301308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/20/2023] [Accepted: 06/20/2023] [Indexed: 06/21/2023]
Abstract
We have quantum chemically studied the influence of ring strain on the competition between the two mechanistically different SN 2 and E2 pathways using a series of archetypal ethers as substrate in combination with a diverse set of Lewis bases (F- , Cl- , Br- , HO- , H3 CO- , HS- , H3 CS- ), using relativistic density functional theory at ZORA-OLYP/QZ4P. The ring strain in the substrate is systematically increased on going from a model acyclic ether to a 6- to 5- to 4- to 3-membered ether ring. We have found that the activation energy of the SN 2 pathway sharply decreases when the ring strain of the system is increased, thus on going from large to small cyclic ethers, the SN 2 reactivity increases. In contrast, the activation energy of the E2 pathway generally rises along this same series, that is, from large to small cyclic ethers. The opposing reactivity trends induce a mechanistic switch in the preferred reaction pathway for strong Lewis bases from E2, for large cyclic substrates, to SN 2, for small cyclic substrates. Weak Lewis bases are unable to overcome the higher intrinsic distortivity of the E2 pathway and, therefore, always favor the less distortive SN 2 reaction.
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Affiliation(s)
- Thomas Hansen
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - Pascal Vermeeren
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - Kim W J Zijderveld
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - F Matthias Bickelhaupt
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
- Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (The, Netherlands
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
| | - Trevor A Hamlin
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
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Zhen W, Zhao S, Fu G, Wang H, Sun J, Yang L, Zhang J. Effects of Methyl Substitution and Leaving Group on E2/S N2 Competition for Reactions of F - with RY (R = CH 3, C 2H 5, iC 3H 7, tC 4H 9; Y = Cl, I). Molecules 2023; 28:6269. [PMID: 37687098 PMCID: PMC10488877 DOI: 10.3390/molecules28176269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
The competition between base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) is of significant importance in organic chemistry and is influenced by many factors. The electronic structure calculations for the gas-phase reactions of F- + RY (R = CH3, C2H5, iC3H7, tC4H9, and Y = Cl, I) are executed at the MP2 level with aug-cc-pVDZ or ECP/d basis set to investigate the α-methyl substitution effect. The variation in barrier height, reaction enthalpy, and competition of SN2/E2 as a function of methyl-substitution and leaving group ability has been emphasized. And the nature of these rules has been explored. As the degree of methyl substitution on α-carbon increases, the E2 channel becomes more competitive and dominant with R varying from C2H5, iC3H7, to tC4H9. Energy decomposition analysis offers new insights into the competition between E2 and SN2 processes, which suggests that the drop in interaction energy with an increasing degree of substitution cannot compensate for the rapid growth of preparation energy, leading to a rapid increase in the SN2 energy barrier. By altering the leaving group from Cl to I, the barriers of both SN2 and E2 monotonically decrease, and, with the increased number of substituents, they reduce more dramatically, which is attributed to the looser transition state structures with the stronger leaving group ability. Interestingly, ∆E0‡ exhibits a positive linear correlation with reaction enthalpy (∆H) and halogen electronegativity. With the added number of substituents, the differences in ∆E0‡ and ∆H between Y = Cl and I likewise exhibit good linearity.
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Affiliation(s)
| | | | | | | | | | - Li Yang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China; (W.Z.); (S.Z.); (G.F.); (H.W.); (J.S.)
| | - Jiaxu Zhang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China; (W.Z.); (S.Z.); (G.F.); (H.W.); (J.S.)
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7
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Marforio TD, Tomasini M, Bottoni A, Zerbetto F, Mattioli EJ, Calvaresi M. Deciphering the Reactive Pathways of Competitive Reactions inside Carbon Nanotubes. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 13:8. [PMID: 36615918 PMCID: PMC9823513 DOI: 10.3390/nano13010008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/16/2022] [Accepted: 12/17/2022] [Indexed: 06/17/2023]
Abstract
Nanoscale control of chemical reactivity, manipulation of reaction pathways, and ultimately driving the outcome of chemical reactions are quickly becoming reality. A variety of tools are concurring to establish such capability. The confinement of guest molecules inside nanoreactors, such as the hollow nanostructures of carbon nanotubes (CNTs), is a straightforward and highly fascinating approach. It mechanically hinders some molecular movements but also decreases the free energy of translation of the system with respect to that of a macroscopic solution. Here, we examined, at the quantum mechanics/molecular mechanics (QM/MM) level, the effect of confinement inside CNTs on nucleophilic substitution (SN2) and elimination (syn-E2 and anti-E2) using as a model system the reaction between ethyl chloride and chloride. Our results show that the three reaction mechanisms are kinetically and thermodynamically affected by the CNT host. The size of the nanoreactor, i.e., the CNT diameter, represents the key factor to control the energy profiles of the reactions. A careful analysis of the interactions between the CNTs and the reactive system allowed us to identify the driving force of the catalytic process. The electrostatic term controls the reaction kinetics in the SN2 and syn/anti-E2 reactions. The van der Waals interactions play an important role in the stabilization of the product of the elimination process.
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Affiliation(s)
- Tainah Dorina Marforio
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
- Center for Chemical Catalysis—C3, Alma Mater Studiorum—Università di Bologna, Via Selmi 2, 40126 Bologna, Italy
| | - Michele Tomasini
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
| | - Andrea Bottoni
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
| | - Francesco Zerbetto
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
| | - Edoardo Jun Mattioli
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
- Center for Chemical Catalysis—C3, Alma Mater Studiorum—Università di Bologna, Via Selmi 2, 40126 Bologna, Italy
| | - Matteo Calvaresi
- Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum-Università di Bologna, Via Francesco Selmi 2, 40126 Bologna, Italy
- Center for Chemical Catalysis—C3, Alma Mater Studiorum—Università di Bologna, Via Selmi 2, 40126 Bologna, Italy
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Junxi L, Fupeng Z, Bomiao Q, Weimin J, Hongqiang L, Qiong S. Reaction of CHCl•- with HCHO and H2O: A theoretical study. COMPUT THEOR CHEM 2022. [DOI: 10.1016/j.comptc.2022.113932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Hansen T, Nin-Hill A, Codée JDC, Hamlin TA, Rovira C. Rational Tuning of the Reactivity of Three-Membered Heterocycle Ring Openings via S N 2 Reactions. Chemistry 2022; 28:e202201649. [PMID: 35896443 DOI: 10.1002/chem.202201649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Indexed: 01/07/2023]
Abstract
The development of small-molecule covalent inhibitors and probes continuously pushes the rapidly evolving field of chemical biology forward. A key element in these molecular tool compounds is the "electrophilic trap" that allows a covalent linkage with the target enzyme. The reactivity of this entity needs to be well balanced to effectively trap the desired enzyme, while not being attacked by off-target nucleophiles. Here we investigate the intrinsic reactivity of substrates containing a class of widely used electrophilic traps, the three-membered heterocycles with a nitrogen (aziridine), phosphorus (phosphirane), oxygen (epoxide) or sulfur atom (thiirane) as heteroatom. Using quantum chemical approaches, we studied the conformational flexibility and nucleophilic ring opening of a series of model substrates, in which these electrophilic traps are mounted on a cyclohexene scaffold (C6 H10 Y with Y=NH, PH, O, S). It was revealed that the activation energy of the ring opening does not necessarily follow the trend that is expected from C-Y leaving-group bond strength, but steeply decreases from Y=NH, to PH, to O, to S. We illustrate that the HOMONu -LUMOSubstrate interaction is an all-important factor for the observed reactivity. In addition, we show that the activation energy of aziridines and phosphiranes can be tuned far below that of the corresponding epoxides and thiiranes by the addition of proper electron-withdrawing ring substituents. Our results provide mechanistic insights to rationally tune the reactivity of this class of popular electrophilic traps and can guide the experimental design of covalent inhibitors and probes for enzymatic activity.
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Affiliation(s)
- Thomas Hansen
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) &, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028, Barcelona, Spain.,Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam (The, Netherlands
| | - Alba Nin-Hill
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) &, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028, Barcelona, Spain
| | - Jeroen D C Codée
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden (The, Netherlands
| | - Trevor A Hamlin
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam (The, Netherlands
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) &, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), 08020, Barcelona, Spain
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Zhao S, Fu G, Zhen W, Yang L, Sun J, Zhang J. Reaction mechanism conversion induced by the contest of nucleophile and leaving group. Phys Chem Chem Phys 2022; 24:24146-24154. [PMID: 36168813 DOI: 10.1039/d2cp01987f] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Direct dynamic simulations have been employed to investigate the OH- + CH3Cl reaction with the chosen B3LYP/aug-cc-pVDZ method. The calculated rate coefficient for the bimolecular nucleophilic substitution reaction (SN2), 1.0 × 10-9 cm3 mol-1 s-1 at 300 K, agrees well with the experimental result of (1.3-1.6) × 10-9 cm3 mol-1 s-1. The simulations reveal that the majority of the SN2 reactions are temporarily trapped in the hydrogen-bonded complex at Ecoll = 0.89 kcal mol-1. Importantly, the influences of the leaving group and nucleophile have been discussed by comparisons of X- + CH3Y (X = F, OH; Y = Cl, I) reactions. For the X = F- reactions, the reaction probability of SN2 increases along the increased leaving group ability Cl < I, suggesting that the thermodynamic factor plays a key role. The indirect mechanisms were found to be dominant for both reactions. In contrast, for X = OH-, the fraction of SN2 drops with the enhanced leaving group ability. In particular, a dramatic transition occurs for the dominant atomic reaction mechanisms, i.e., from complex-mediated indirect to direct, implying an interesting contest between the leaving group and the nucleophile and the importance of the dynamic factors, i.e., the dipole moment, steric hindrance, and electronegativity.
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Affiliation(s)
- Siwei Zhao
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Gang Fu
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Wenqing Zhen
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China.
| | - Li Yang
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China. .,State Key Lab of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jianmin Sun
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China. .,State Key Lab of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jiaxu Zhang
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China. .,State Key Lab of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
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11
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Wu X, Zhang S, Xie J. Investigating the competing E2 and S N2 mechanisms for the microsolvated HO -(H 2O) n=0-4 + CH 3CH 2X (X = Cl, Br, I) reactions. Phys Chem Chem Phys 2022; 24:12993-13005. [PMID: 35582984 DOI: 10.1039/d1cp04010c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We characterized the anti-E2, syn-E2, inv-SN2, and ret-SN2 reaction channels for the reaction of microsolvated HO-(H2O)n anions with CH3CH2X (X = Cl, Br, I), using the CCSD(T)/PP/t//MP2/ECP/d level method, to understand how a solvent influences the competing E2 and SN2 reactions. The calculated sequence of barrier for the four channels is ret-SN2 > syn-E2 > anti-E2 > inv-SN2. The barrier heights increase with incremental hydration as the system transfers from the gas phase to microsolvation, and to bulk solvation (using the PCM implicit solvent model). As the degree of hydration n increases, good correlations have been found between barrier heights and several thermodynamic, geometric and charge parameters, including the reaction enthalpy, proton/ethyl-cation affinity of the hydrated nucleophile, geometric looseness (%L‡) and asymmetry (%AS‡) and charge asymmetry (Δq(X-O)) of the transition structures. Under a molecular orbital scheme, the HOMOs of nucleophiles are stabilized by stepwise hydration, explaining the rise in the barriers. Considering the effect of the leaving group, the barrier heights exhibit linear correlation with the halogen electronegativity and H-acidity of substrate CH3CH2X. In terms of E2/SN2 competition, the barrier difference, , first increases then decreases as the number of explicit water molecules increases, under both microsolvation and bulk solvation conditions, but the inv-SN2 pathway is always favored over the anti-E2 pathway. Energy decomposition analysis attributes the increase of barrier difference to the greater geometric distortion in the anti-E2 transition structure.
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Affiliation(s)
- Xiangyu Wu
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
| | - Shaowen Zhang
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
| | - Jing Xie
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
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12
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Tajti V, Czakó G. Vibrational mode-specific dynamics of the F - + CH 3CH 2Cl multi-channel reaction. Phys Chem Chem Phys 2022; 24:8166-8181. [PMID: 35343535 DOI: 10.1039/d2cp00685e] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigate the mode-specific dynamics of the ground-state, C-Cl stretching (v10), CH2 wagging (v7), sym-CH2 stretching (v1), and sym-CH3 stretching (v3) excited F- + CH3CH2Cl(vk = 0, 1) [k = 10, 7, 1, 3] → Cl- + CH3CH2F (SN2), HF + CH3CHCl-, FH⋯Cl- + C2H4, and Cl- + HF + C2H4 (E2) reactions using a full-dimensional high-level analytical global potential energy surface and the quasi-classical trajectory method. Excitation of the C-Cl stretching, CH2 stretching, and CH2/CH3 stretching modes enhances the SN2, proton abstraction, and FH⋯Cl- and E2 channels, respectively. Anti-E2 dominates over syn-E2 (kinetic anti-E2 preference) and the thermodynamically-favored SN2 (wider reactive anti-E2 attack angle range). The direct (a) SN2, (b) proton abstraction, (c) FH⋯Cl- + C2H4, (d) syn-E2, and (e) anti-E2 channels proceed with (a) back-side/backward, (b) isotropic/forward, (c) side-on/forward, (d) front-side/forward, and (e) back-side/forward attack/scattering, respectively. The HF products are vibrationally cold, especially for proton abstraction, and their rotational excitation increases for proton abstraction, anti-E2, and syn-E2, in order. Product internal-energy and mode-specific vibrational distributions show that CH3CH2F is internally hot with significant C-F stretching and CH2 wagging excitations, whereas C2H4 is colder. One-dimensional Gaussian binning technique is proved to solve the normal mode analysis failure caused by methyl internal rotation.
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Affiliation(s)
- Viktor Tajti
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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13
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Ji X, Xie J. Proton transfer-induced competing product channels of microsolvated Y -(H 2O) n + CH 3I (Y = F, Cl, Br, I) reactions. Phys Chem Chem Phys 2022; 24:7539-7550. [PMID: 35289813 DOI: 10.1039/d1cp04873b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The potential energy profiles of three proton transfer-involved product channels for the reactions of Y-(H2O)1,2 + CH3I (Y = F, Cl, Br, I) were characterized using the B97-1/ECP/d method. These three channels include the (1) PTCH3 product channel that transfers a proton from methyl to nucleophile, (2) HO--induced nucleophilic substitution (HO--SN2) product channel, and (3) oxide ion substitution (OIS) product channel that gives CH3O- and HY products. The reaction enthalpies and barrier heights follow the order OIS > PTCH3 > HO--SN2 > Y--SN2, and thus HO--SN2 can compete with the most favored Y--SN2 product channel under singly-/doubly-hydrated conditions, while the PTCH3 channel only occurs under high collision energy and the OIS channel is the least probable. All product channels share the same pre-reaction complex, Y-(H2O)n-CH3I, in the entrance of the potential energy profile, signifying the importance of the pre-reaction complex. For HO-/Y--SN2 channels, we considered front-side attack, back-side attack, and halogen-bonded complex mechanisms. Incremental hydration increases the barriers of both HO-/Y--SN2 channels as well as their barrier difference, implying that the HO--SN2 channel becomes less important when further hydrated. Varying the nucleophile Y- from F- to I- also increases the barrier heights and barrier difference, which correlates with the proton affinity of the nucleophiles. Energy decomposition analyses show that both the orbital interaction energy and structural deformation energy of the transition states determine the SN2 barrier change trend with incremental hydration and varying Y-. In brief, this work computes the comprehensive potential energy surfaces of the HO--SN2 and PTCH3 channels and shows how proton transfer affects the microsolvated Y-(H2O)1,2 + CH3I reaction by competing with the traditional Y--SN2 channel.
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Affiliation(s)
- Xiaoyan Ji
- Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
| | - Jing Xie
- Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
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14
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Jackson R, Zhang W, Pearson J. TSNet: predicting transition state structures with tensor field networks and transfer learning. Chem Sci 2021; 12:10022-10040. [PMID: 34377396 PMCID: PMC8317659 DOI: 10.1039/d1sc01206a] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 06/21/2021] [Indexed: 12/14/2022] Open
Abstract
Transition states are among the most important molecular structures in chemistry, critical to a variety of fields such as reaction kinetics, catalyst design, and the study of protein function. However, transition states are very unstable, typically only existing on the order of femtoseconds. The transient nature of these structures makes them incredibly difficult to study, thus chemists often turn to simulation. Unfortunately, computer simulation of transition states is also challenging, as they are first-order saddle points on highly dimensional mathematical surfaces. Locating these points is resource intensive and unreliable, resulting in methods which can take very long to converge. Machine learning, a relatively novel class of algorithm, has led to radical changes in several fields of computation, including computer vision and natural language processing due to its aptitude for highly accurate function approximation. While machine learning has been widely adopted throughout computational chemistry as a lightweight alternative to costly quantum mechanical calculations, little research has been pursued which utilizes machine learning for transition state structure optimization. In this paper TSNet is presented, a new end-to-end Siamese message-passing neural network based on tensor field networks shown to be capable of predicting transition state geometries. Also presented is a small dataset of SN2 reactions which includes transition state structures - the first of its kind built specifically for machine learning. Finally, transfer learning, a low data remedial technique, is explored to understand the viability of pretraining TSNet on widely available chemical data may provide better starting points during training, faster convergence, and lower loss values. Aspects of the new dataset and model shall be discussed in detail, along with motivations and general outlook on the future of machine learning-based transition state prediction.
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Affiliation(s)
- Riley Jackson
- Department of Chemistry, University of Prince Edward Island Canada
| | - Wenyuan Zhang
- Department of Chemistry, University of Prince Edward Island Canada
| | - Jason Pearson
- Department of Chemistry, University of Prince Edward Island Canada
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15
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Stuyver T, Shaik S. Resolving Entangled Reactivity Modes through External Electric Fields and Substitution: Application to E 2/S N2 Reactions. J Org Chem 2021; 86:9030-9039. [PMID: 34152765 DOI: 10.1021/acs.joc.1c01010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we explore strategies to resolve entangled reactivity modes. More specifically, we consider the competition between SN2 and E2 reaction pathways for alkyl halides and nucleophiles/bases. We first demonstrate that the emergence of an E2-preference is associated with an enhancement of the magnitude of the resonance stabilization in the transition-state (TS) region, resulting from the improved mixing of electrostatically stabilized valence bond structures into the TS wavefunction. Subsequently, we show that the TS resonance energy can be tuned selectively and rationally either through the application of an oriented external electric field directed along the C-C axis of the alkyl halide or through a regular substitution approach of the C-C moiety. We end our study by demonstrating that the insights gained from our analysis enable one to rationalize the main reactivity trends emerging from a recently published large database of competing SN2 and E2 reaction pathways.
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Affiliation(s)
- Thijs Stuyver
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Sason Shaik
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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16
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Tasi DA, Tokaji C, Czakó G. A benchmark ab initio study of the complex potential energy surfaces of the OH - + CH 3CH 2Y [Y = F, Cl, Br, I] reactions. Phys Chem Chem Phys 2021; 23:13526-13534. [PMID: 34132273 DOI: 10.1039/d1cp01303c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We provide the first benchmark characterization of the OH- + CH3CH2Y [Y = F, Cl, Br, I] reactions utilizing the high-level explicitly-correlated CCSD(T)-F12b method with the aug-cc-pVnZ [n = 2(D), 3(T), 4(Q)] basis sets. We explore and analyze the stationary points of the elimination (E2) and substitution (SN2) reactions, including anti-E2, syn-E2, back-side attack, front-side attack, and double inversion. In all cases, SN2 is thermodynamically more preferred than E2. In the entrance channel of SN2 a significant front-side complex formation is revealed, and in the product channel the global minimum of the title reactions is obtained at the hydrogen-bonded CH3CH2OHY- complex. Similar to the OH- + CH3Y reactions, double inversion can proceed via a notably lower-energy pathway than front-side attack, moreover, for Y = I double inversion becomes barrier-less. For the transition state of the anti-E2, a prominent ZPE effect emerges, giving an opportunity for a kinetically more favored pathway than back-side attack. In addition to SN2 and E2, other possible product channels are considered, and in most cases, the benchmark reaction enthalpies are in excellent agreement with the experimental data.
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Affiliation(s)
- Domonkos A Tasi
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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17
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Jeanmairet G, Levesque M, Borgis D. Tackling Solvent Effects by Coupling Electronic and Molecular Density Functional Theory. J Chem Theory Comput 2020; 16:7123-7134. [PMID: 32894674 DOI: 10.1021/acs.jctc.0c00729] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Solvation effects can have a tremendous influence on chemical reactions. However, precise quantum chemistry calculations are most often done either in vacuum neglecting the role of the solvent or using continuum solvent model ignoring its molecular nature. We propose a new method coupling a quantum description of the solute using electronic density functional theory with a classical grand-canonical treatment of the solvent using molecular density functional theory. Unlike a previous work, both densities are minimized self-consistently, accounting for mutual polarization of the molecular solvent and the solute. The electrostatic interaction is accounted using the full electron density of the solute rather than fitted point charges. The introduced methodology represents a good compromise between the two main strategies to tackle solvation effects in quantum calculation. It is computationally more effective than a direct quantum mechanics/molecular mechanics coupling, requiring the exploration of many solvent configurations. Compared to continuum methods, it retains the full molecular-level description of the solvent. We validate this new framework onto two usual benchmark systems: a water solvated in water and the symmetrical nucleophilic substitution between chloromethane and chloride in water. The prediction for the free energy profiles are not yet fully quantitative compared to experimental data, but the most important features are qualitatively recovered. The method provides a detailed molecular picture of the evolution of the solvent structure along the reaction pathway.
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Affiliation(s)
- Guillaume Jeanmairet
- Sorbonne Université, CNRS, Physico-Chimie des Électrolytes et Nanosystèmes, Interfaciaux, PHENIX, F-75005 Paris, France.,Réseau sur le Stockage Électrochimique de l'Énergie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France
| | - Maximilien Levesque
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne, Université, CNRS, 75005 Paris, France.,Aqemia, 75006 Paris, France
| | - Daniel Borgis
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne, Université, CNRS, 75005 Paris, France.,Maison de la Simulation, CEA, CNRS, Université Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
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18
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Vermeeren P, Hansen T, Grasser M, Silva DR, Hamlin TA, Bickelhaupt FM. S N2 versus E2 Competition of F - and PH 2- Revisited. J Org Chem 2020; 85:14087-14093. [PMID: 33079542 PMCID: PMC7656514 DOI: 10.1021/acs.joc.0c02112] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have quantum chemically analyzed the competition between the bimolecular nucleophilic substitution (SN2) and base-induced elimination (E2) pathways for F- + CH3CH2Cl and PH2- + CH3CH2Cl using the activation strain model and Kohn-Sham molecular orbital theory at ZORA-OLYP/QZ4P. Herein, we correct an earlier study that intuitively attributed the mechanistic preferences of F- and PH2-, i.e., E2 and SN2, respectively, to a supposedly unfavorable shift in the polarity of the abstracted β-proton along the PH2--induced E2 pathway while claiming that ″...no correlation between the thermodynamic basicity and E2 rate should be expected.″ Our analyses, however, unequivocally show that it is simply the 6 kcal mol-1 higher proton affinity of F- that enables this base to engage in a more stabilizing orbital interaction with CH3CH2Cl and hence to preferentially react via the E2 pathway, despite the higher characteristic distortivity (more destabilizing activation strain) associated with this pathway. On the other hand, the less basic PH2- has a weaker stabilizing interaction with CH3CH2Cl and is, therefore, unable to overcome the characteristic distortivity of the E2 pathway. Therefore, the mechanistic preference of PH2- is steered to the SN2 reaction channel (less-destabilizing activation strain).
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Affiliation(s)
- Pascal Vermeeren
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Thomas Hansen
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Maxime Grasser
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Daniela Rodrigues Silva
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Departamento de Quı́mica, Universidade Federal de Lavras, Lavras, Minas Gerais 37200-900, Brazil
| | - Trevor A Hamlin
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - F Matthias Bickelhaupt
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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19
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Hansen T, Vermeeren P, Haim A, van Dorp MJH, Codée JDC, Bickelhaupt FM, Hamlin TA. Regioselectivity of Epoxide Ring-Openings via SN
2 Reactions Under Basic and Acidic Conditions. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000590] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Thomas Hansen
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
- Leiden Institute of Chemistry; Leiden University; Einsteinweg 55 2333 CC Leiden The Netherlands
| | - Pascal Vermeeren
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
| | - Anissa Haim
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
| | - Maarten J. H. van Dorp
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
| | - Jeroen D. C. Codée
- Leiden Institute of Chemistry; Leiden University; Einsteinweg 55 2333 CC Leiden The Netherlands
| | - F. Matthias Bickelhaupt
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
- Institute for Molecules and Materials (IMM); Radboud University; Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands
| | - Trevor A. Hamlin
- Department of Theoretical Chemistry; Amsterdam Institute of Molecular and Life Sciences (AIMMS); Amsterdam Center for Multiscale Modeling (ACMM); Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
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20
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Understanding chemical reactivity using the activation strain model. Nat Protoc 2020; 15:649-667. [PMID: 31925400 DOI: 10.1038/s41596-019-0265-0] [Citation(s) in RCA: 160] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 10/29/2019] [Indexed: 12/20/2022]
Abstract
Understanding chemical reactivity through the use of state-of-the-art computational techniques enables chemists to both predict reactivity and rationally design novel reactions. This protocol aims to provide chemists with the tools to implement a powerful and robust method for analyzing and understanding any chemical reaction using PyFrag 2019. The approach is based on the so-called activation strain model (ASM) of reactivity, which relates the relative energy of a molecular system to the sum of the energies required to distort the reactants into the geometries required to react plus the strength of their mutual interactions. Other available methods analyze only a stationary point on the potential energy surface, but our methodology analyzes the change in energy along a reaction coordinate. The use of this methodology has been proven to be critical to the understanding of reactions, spanning the realms of the inorganic and organic, as well as the supramolecular and biochemical, fields. This protocol provides step-by-step instructions-starting from the optimization of the stationary points and extending through calculation of the potential energy surface and analysis of the trend-decisive energy terms-that can serve as a guide for carrying out the analysis of any given reaction of interest within hours to days, depending on the size of the molecular system.
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21
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Meyer J, Carrascosa E, Michaelsen T, Bastian B, Li A, Guo H, Wester R. Unexpected Indirect Dynamics in Base-Induced Elimination. J Am Chem Soc 2019; 141:20300-20308. [DOI: 10.1021/jacs.9b10575] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Eduardo Carrascosa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Björn Bastian
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Anyang Li
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Ministry of Education, College of Chemistry and Materials Science, Northwest Universtiy, 710127 Xian, People’s Republic of China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
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22
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Li J, Meng X, Hu C, Su Z. Cooperative Catalysis of Chiral Guanidine and Rh 2(OAc) 4 in Asymmetric O-H Insertion of Carboxylic Acid: A Theoretical Investigation. J Org Chem 2019; 84:15020-15031. [PMID: 31675228 DOI: 10.1021/acs.joc.8b02850] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We reported a mechanistic study on asymmetric O-H insertion reaction of α-diazoester with carboxylic acid using Rh2(OAc)4/chiral guanidine-amide as the cocatalyst by density functional theory [B3LYP-D3(BJ)/def2-TZVP//B3LYP-D3(BJ)/[6-31G**, SDD] (SMD, Et2O)]. The catalytic reaction included two stages: (i) formation of Rh-carbene species, subsequently by the construction of C-O bond forming enol and (ii) chiral guanidinium salt-assisted H-transfer to the enol. In cooperative catalysis, Rh2(OAc)4 helped to form an enol intermediate via high-reactivity Rh-carbene species, while the in situ-formed guanidium carboxylate acted as a chiral proton shuttle to construct a hydrogen bonding net for the stereo-determinant protonation. The repulsions between the phenyl group of the enol intermediate and the cyclohexyl as well as the ortho-substituted isopropyl group of chiral guanidine played important roles in controlling stereoselectivity. A disadvantageous steric arrangement in si-face attack weakened the stabilizing electrostatic and orbital interaction of reacting species in the H-transfer step, enhancing the pathway to form a predominant product with R-configuration in the two competing pathways. A model was proposed to explain the asymmetric induction of chiral guanidine-amide in protonation.
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Affiliation(s)
- Jing Li
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry , Sichuan University , Chengdu , Sichuan 610064 , P.R. China
| | - Xiangxiang Meng
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry , Sichuan University , Chengdu , Sichuan 610064 , P.R. China
| | - Changwei Hu
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry , Sichuan University , Chengdu , Sichuan 610064 , P.R. China
| | - Zhishan Su
- Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry , Sichuan University , Chengdu , Sichuan 610064 , P.R. China
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23
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Effect of solvent polarity on the potential energy surface in the SN2 reaction of F− + CH3Cl. COMPUT THEOR CHEM 2019. [DOI: 10.1016/j.comptc.2019.01.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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24
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Liu X, Zhang J, Yang L, Hase WL. How a Solvent Molecule Affects Competing Elimination and Substitution Dynamics. Insight into Mechanism Evolution with Increased Solvation. J Am Chem Soc 2018; 140:10995-11005. [DOI: 10.1021/jacs.8b04529] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xu Liu
- State Key Laboratory of Advanced Welding and Joining, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jiaxu Zhang
- State Key Laboratory of Advanced Welding and Joining, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Li Yang
- State Key Laboratory of Advanced Welding and Joining, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - William L. Hase
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
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25
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Satpathy L, Sahu PK, Behera PK, Mishra BK. Solvent Effect on the Potential Energy Surfaces of the F - + CH 3CH 2Br Reaction. J Phys Chem A 2018; 122:5861-5869. [PMID: 29909618 DOI: 10.1021/acs.jpca.8b02687] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although substantial work has been undertaken on reaction pathways involved in base-promoted elimination reactions and bimolecular nucleophilic substitution reaction of F- on CH3CH2X (X = Cl, Br, I), the effect of solvents with varying dielectric constants on the stereochemistry of each of the reaction species involved across the reaction profile have not yet been clearly understood. The present investigation reports the effect of solvents on the potential energy surfaces (PES) and structures of the species appearing in the reaction pathway of F- with bromoethane. The PESs in the gas phase have been computed at MP2 level and CCSD(T) level. The performance of several hybrid density functional, such as B3LYP, M06, M06L, BHandH, X3LYP, M05, M05-2X, and M06-2X have also been investigated toward describing the elimination and nucleophilic substitution reactions. With respect to MAE values and to make the computation cost-effective, we have explored the implicit continuum solvent model, CPCM in solvents like cyclohexane, methanol, acetonitrile, dimethyl sulfoxide and water. The reactant complexes proceed through the subsequent steps to produce fluoroethane as the substitution product and ethylene as one of the elimination products. For elimination reaction both syn and anti elimination have been explored. The calculated relatives energies values, which are negative in the gas phase, are found to be positive in polar solvents since the point charge in the separated reactants are more stabilized than the dispersed charge in the transient complex, which has also been analyzed through NBO analysis.
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Affiliation(s)
- Lopamudra Satpathy
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
| | - Prabhat K Sahu
- Computational Modeling Research Laboratory , School of Chemistry Sambalpur University , Jyoti Vihar 768 019 , India
| | - Pradipta K Behera
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
| | - Bijay K Mishra
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
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26
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Hamlin TA, Swart M, Bickelhaupt FM. Nucleophilic Substitution (S N 2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent. Chemphyschem 2018; 19:1315-1330. [PMID: 29542853 PMCID: PMC6001448 DOI: 10.1002/cphc.201701363] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Indexed: 11/12/2022]
Abstract
The reaction potential energy surface (PES), and thus the mechanism of bimolecular nucleophilic substitution (SN 2), depends profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the SN 2 mechanism. One of the most striking effects is the transition from a double-well to a single-well PES when the central atom is changed from a second-period (e. g. carbon) to a higher-period element (e.g, silicon, germanium). Variations in nucleophilicity, leaving group ability, and bulky substituents around a second-row element central atom can then be exploited to change the single-well PES back into a double-well. Reversely, these variations can also be used to produce a single-well PES for second-period elements, for example, a stable pentavalent carbon species.
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Affiliation(s)
- Trevor A. Hamlin
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
| | - Marcel Swart
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
- Institut de Química Computacional I Catàlisi and Department de QuímicaUniversitat de Girona17003GironaSpain
- ICREAPg. Lluís Companys 2308010BarcelonaSpain
| | - F. Matthias Bickelhaupt
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
- Institute of Molecules and Materials (IMM)Radboud UniversityHeyendaalseweg 1356525 AJNijmegenThe Netherlands
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27
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Hamlin TA, van Beek B, Wolters LP, Bickelhaupt FM. Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects. Chemistry 2018; 24:5927-5938. [PMID: 29457865 PMCID: PMC5947303 DOI: 10.1002/chem.201706075] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Indexed: 12/23/2022]
Abstract
We have quantum chemically studied the effect of various polar and apolar solvents on the shape of the potential energy surface (PES) of a diverse collection of archetypal nucleophilic substitution reactions at carbon, silicon, phosphorus, and arsenic by using density functional theory at the OLYP/TZ2P level. In the gas phase, all our model SN 2 reactions have single-well PESs, except for the nucleophilic substitution reaction at carbon (SN 2@C), which has a double-well energy profile. The presence of the solvent can have a significant effect on the shape of the PES and, thus, on the nature of the SN 2 process. Solvation energies, charges on the nucleophile or leaving group, and structural features are compared for the various SN 2 reactions in a spectrum of solvents. We demonstrate how solvation can change the shape of the PES, depending not only on the polarity of the solvent, but also on how the charge is distributed over the interacting molecular moieties during different stages of the reaction. In the case of a nucleophilic substitution at three-coordinate phosphorus, the reaction can be made to proceed through a single-well [no transition state (TS)], bimodal barrier (two TSs), and then through a unimodal transition state (one TS) simply by increasing the polarity of the solvent.
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Affiliation(s)
- Trevor A. Hamlin
- Department of Theoretical ChemistryAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
| | - Bas van Beek
- Department of Theoretical ChemistryAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
| | - Lando P. Wolters
- Department of Theoretical ChemistryAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
| | - F. Matthias Bickelhaupt
- Department of Theoretical ChemistryAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
- Institute of Molecules and Materials (IMM)Radboud University NijmegenHeyendaalseweg 1356525 AJNijmegenThe Netherlands
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28
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Miranda-Rojas S, Fernández I, Kästner J, Toro-Labbé A, Mendizábal F. Unraveling the Nature of the Catalytic Power of Fluoroacetate Dehalogenase. ChemCatChem 2018. [DOI: 10.1002/cctc.201701517] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sebastián Miranda-Rojas
- Departamento de Ciencias Químicas; Facultad de Ciencias Exactas; Universidad Andres Bello; Av. República 275 Santiago Chile
| | - Israel Fernández
- Departamento de Química Orgánica I and Centro de Innovación en, Química Avanzada (ORFEO-CINQA); Facultad de Ciencias Químicas; Universidad Complutense de Madrid; 28040- Madrid Spain
| | - Johannes Kästner
- Institut für Theoretische Chemie; Universität Stuttgart; Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Alejandro Toro-Labbé
- Laboratorio de Química Teórica Computacional; Facultad de Química; Pontifica Universidad Católica de Chile; Av. Vicuña Mackenna 4860, Macul Santiago Chile
| | - Fernando Mendizábal
- Departamento de Química; Facultad de Ciencias; Universidad de Chile; Las Palmeras 3425, Ñuñoa Santiago Chile
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29
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Carrascosa E, Meyer J, Michaelsen T, Stei M, Wester R. Conservation of direct dynamics in sterically hindered S N2/E2 reactions. Chem Sci 2017; 9:693-701. [PMID: 29629138 PMCID: PMC5869569 DOI: 10.1039/c7sc04415a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 11/09/2017] [Indexed: 11/21/2022] Open
Abstract
Nucleophilic substitution (SN2) and base-induced elimination (E2), two indispensable reactions in organic synthesis, are commonly assumed to proceed under stereospecific conditions. Understanding the way in which the reactants pre-orient in these reactions, that is its stereodynamics, is essential in order to achieve a detailed atomistic picture and control over such processes. Using crossed beam velocity map imaging, we study the effect of steric hindrance in reactions of Cl- and CN- with increasingly methylated alkyl iodides by monitoring the product ion energy and scattering angle. For both attacking anions the rebound mechanism, indicative of a direct SN2 pathway, is found to contribute to the reaction at high relative collision energies despite being increasingly hindered. An additional forward scattering mechanism, ascribed to a direct E2 reaction, also contributes at these energies. Inspection of the product energy distributions confirms the direct and fast character of both mechanisms as opposed to an indirect reaction mechanism which leads to statistical energy redistribution in the reaction complex. This work demonstrates that nonstatistical dynamics and energetics govern SN2 and E2 pathways even in sterically hindered exchange reaction systems.
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Affiliation(s)
- Eduardo Carrascosa
- Institut für Ionenphysik und Angewandte Physik , Universität Innsbruck , Technikerstraße 25 , 6020 Innsbruck , Austria . ; Tel: +43 512 507 52620
| | - Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik , Universität Innsbruck , Technikerstraße 25 , 6020 Innsbruck , Austria . ; Tel: +43 512 507 52620
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik , Universität Innsbruck , Technikerstraße 25 , 6020 Innsbruck , Austria . ; Tel: +43 512 507 52620
| | - Martin Stei
- Institut für Ionenphysik und Angewandte Physik , Universität Innsbruck , Technikerstraße 25 , 6020 Innsbruck , Austria . ; Tel: +43 512 507 52620
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik , Universität Innsbruck , Technikerstraße 25 , 6020 Innsbruck , Austria . ; Tel: +43 512 507 52620
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30
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Mándity IM, Nekkaa I, Paragi G, Fülöp F. Homochirality of β-Peptides: A Significant Biomimetic Property of Unnatural Systems. ChemistryOpen 2017; 6:492-496. [PMID: 28794942 PMCID: PMC5542748 DOI: 10.1002/open.201700078] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Indexed: 01/10/2023] Open
Abstract
Homochirality, an interesting phenomenon of life, is mainly an unresolved problem and was thought to be a property of living matter. Herein, we show that artificial β-peptides have the tendency toward homochiral diastereoselective chain elongation. Chain-length-dependent stereochemical discrimination was investigated in the synthesis of foldamers with various side chains and secondary structures. It was found that there is a strong tendency toward the synthesis of homochiral oligomers. The size of the side chain drastically influenced the selectivity of the stereodiscriminative chain-elongation reaction. It is noteworthy that water as the co-solvent increases the selectivity. Such behavior is a novel fundamental biomimetic property of foldamers with a potential of future industrial application.
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Affiliation(s)
- István M. Mándity
- Institute of Pharmaceutical ChemistryUniversity of SzegedEötvös u. 66720SzegedHungary
| | - Imane Nekkaa
- Institute of Pharmaceutical ChemistryUniversity of SzegedEötvös u. 66720SzegedHungary
| | - Gábor Paragi
- MTA-SZTE Supramolecular and Nanostructured Materials Research GroupDóm tér 86720SzegedHungary
| | - Ferenc Fülöp
- Institute of Pharmaceutical ChemistryUniversity of SzegedEötvös u. 66720SzegedHungary
- Research Group of Stereochemistry of the Hungarian Academy of SciencesDóm tér 86720SzegedHungary
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31
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Abstract
The competition between bimolecular nucleophilic substitution and base-induced elimination is of fundamental importance for the synthesis of pure samples in organic chemistry. Many factors that influence this competition have been identified over the years, but the underlying atomistic dynamics have remained difficult to observe. We present product velocity distributions for a series of reactive collisions of the type X− + RY with X and Y denoting the halogen atoms fluorine, chlorine and iodine. By increasing the size of the residue R from methyl to tert-butyl in several steps, we find that the dynamics drastically change from backward to dominant forward scattering of the leaving ion relative to the reactant RY velocity. This characteristic fingerprint is also confirmed by direct dynamics simulations for ethyl as residue and attributed to the dynamics of elimination reactions. This work opens the door to a detailed atomistic understanding of transformation reactions in even larger systems. The competition between chemical reactions critically affects our natural environment and the synthesis of new materials. Here, the authors present an approach to directly image distinct fingerprints of essential organic reactions and monitor their competition as a function of steric substitution.
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32
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Affiliation(s)
- Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria
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33
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Tajti V, Czakó G. Benchmark ab Initio Characterization of the Complex Potential Energy Surface of the F– + CH3CH2Cl Reaction. J Phys Chem A 2017; 121:2847-2854. [DOI: 10.1021/acs.jpca.7b01572] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Viktor Tajti
- Department of Physical Chemistry
and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- Department of Physical Chemistry
and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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34
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Yang L, Zhang J, Xie J, Ma X, Zhang L, Zhao C, Hase WL. Competing E2 and SN2 Mechanisms for the F– + CH3CH2I Reaction. J Phys Chem A 2017; 121:1078-1085. [DOI: 10.1021/acs.jpca.6b09546] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Li Yang
- School
of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
| | - Jiaxu Zhang
- School
of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
| | - Jing Xie
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Xinyou Ma
- Department
of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
| | - Linyao Zhang
- School
of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
| | - Chenyang Zhao
- School
of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
| | - William L. Hase
- Department
of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
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35
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Ribaudo G, Bellanda M, Menegazzo I, Wolters LP, Bortoli M, Ferrer-Sueta G, Zagotto G, Orian L. Mechanistic Insight into the Oxidation of Organic Phenylselenides by H 2 O 2. Chemistry 2017; 23:2405-2422. [PMID: 27935210 DOI: 10.1002/chem.201604915] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Indexed: 12/24/2022]
Abstract
The oxidation of organic phenylselenides by H2 O2 is investigated in model compounds, namely, n-butyl phenyl selenide (PhSe(nBu)), bis(phenylselanyl)methane (PhSeMeSePh), diphenyl diselenide (PhSeSePh), and 1,2-bis(phenylselanyl)ethane (PhSeEtSePh). Through a combined experimental (1 H and 77 Se NMR) and computational approach, we characterize the direct oxidation of monoselenide to selenoxide, the stepwise double oxidation of PhSeMeSePh that leads to different diastereomeric diselenoxides, the complete oxidation of the diphenyldiselenide that leads to selenium-selenium bond cleavage, and the subsequent formation of the phenylseleninic product. The oxidation of PhSeEtSePh also results in the formation of phenylseleninic acid along with 1-(vinylseleninyl)benzene, which is derived from a side elimination reaction. The evidence of a direct mechanism, in addition to an autocatalytic mechanism that emerges from kinetic studies, is discussed. By considering our observations of diselenides with chalcogen atoms that are separated by alkyl spacers of different length, a rationale for the advantage of diselenide versus monoselenide catalysts is presented.
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Affiliation(s)
- Giovanni Ribaudo
- Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, Via Marzolo 5, 35131, Padova, Italy
| | - Massimo Bellanda
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Ileana Menegazzo
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Lando P Wolters
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Marco Bortoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
| | - Gerardo Ferrer-Sueta
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la Repúbica, Igua 4225, Montevideo, Uruguay
| | - Giuseppe Zagotto
- Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, Via Marzolo 5, 35131, Padova, Italy
| | - Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy
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36
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Abstract
![]()
Fundamental
principles that determine chemical reactivity and reaction
mechanisms are the very foundation of chemistry and many related fields
of science. Bimolecular nucleophilic substitutions (SN2)
are among the most common and therefore most important reaction types.
In this report, we examine the trends in the SN2 reactions
with respect to increasing electronegativity of the reaction center
by comparing the well-studied backside SN2 Cl– + CH3Cl with similar Cl– substitutions
on the isoelectronic series with the second period elements N, O,
and F in place of C. Relativistic (ZORA) DFT calculations are used
to construct the gas phase reaction potential energy surfaces (PES),
and activation strain analysis, which allows decomposition of the
PES into the geometrical strain and interaction energy, is employed
to analyze the observed trends. We find that SN2@N and
SN2@O have similar PES to the prototypical SN2@C, with the well-defined reaction complex (RC) local minima and
a central barrier, but all stationary points are, respectively, increasingly
stable in energy. The SN2@F, by contrast, exhibits only
a single-well PES with no barrier. Using the activation strain model,
we show that the trends are due to the interaction energy and originate
mainly from the decreasing energy of the empty acceptor orbital (σ*A–Cl) on the reaction center A in the order of C, N,
O, and F. The decreasing steric congestion around the central atom
is also a likely contributor to this trend. Additional decomposition
of the interaction energy using Kohn–Sham molecular orbital
(KS-MO) theory provides further support for this explanation, as well
as suggesting electrostatic energy as the primary reason for the distinct
single-well PES profile for the FCl reaction.
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Affiliation(s)
- Jan Kubelka
- Department of Chemistry, University of Wyoming , Laramie, Wyoming 82070, United States
| | - F Matthias Bickelhaupt
- Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam , De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Institute for Molecules and Materials (IMM), Radboud University , Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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37
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Carrascosa E, Meyer J, Wester R. Imaging the dynamics of ion–molecule reactions. Chem Soc Rev 2017; 46:7498-7516. [DOI: 10.1039/c7cs00623c] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A range of ion–molecule reactions have been studied in the last years using the crossed-beam ion imaging technique, from charge transfer and proton transfer to nucleophilic substitution and elimination.
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Affiliation(s)
- Eduardo Carrascosa
- Institut für Ionenphysik und Angewandte Physik
- Universität Innsbruck
- 6020 Innsbruck
- Austria
| | - Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik
- Universität Innsbruck
- 6020 Innsbruck
- Austria
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik
- Universität Innsbruck
- 6020 Innsbruck
- Austria
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38
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Proenza YG, de Souza MAF, Longo RL. Dynamical Bifurcation in Gas-Phase XH - + CH 3 Y S N 2 Reactions: The Role of Energy Flow and Redistribution in Avoiding the Minimum Energy Path. Chemistry 2016; 22:16220-16229. [PMID: 27651104 DOI: 10.1002/chem.201602976] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 11/10/2022]
Abstract
The gas-phase reactions of XH- (X=O, S) + CH3 Y (Y=F, Cl, Br) span nearly the whole range of SN 2 pathways, and show an intrinsic reaction coordinate (IRC) (minimum energy path) with a deep well owing to the CH3 XH⋅⋅⋅Y- (or CH3 S- ⋅⋅⋅HF) hydrogen-bonded postreaction complex. MP2 quasiclassical-type direct dynamics starting at the [HX⋅⋅⋅CH3 ⋅⋅⋅Y]- transition-state (TS) structure reveal distinct mechanistic behaviors. Trajectories that yield the separated CH3 XH+Y- (or CH3 S- +HF) products directly are non-IRC, whereas those that sample the CH3 XH⋅⋅⋅Y- (or CH3 S- ⋅⋅⋅HF) complex are IRC. The IRCIRC/non-IRC ratios of 90:10, 40:60, 25:75, 2:98, 0:100, and 0:100 are obtained for (X, Y)=(S, F), (O, F), (S, Cl), (S, Br), (O, Cl), and (O, Br), respectively. The properties of the energy profiles after the TS cannot provide a rationalization of these results. Analysis of the energy flow in dynamics shows that the trajectories cross a dynamical bifurcation, and that the inability to follow the minimum energy path arises from long vibration periods of the X-C⋅⋅⋅Y bending mode. The partition of the available energy to the products into vibrational, rotational, and translational energies reveals that if the vibrational contribution is more than 80 %, non-IRC behavior dominates, unless the relative fraction of the rotational and translational components is similar, in which case a richer dynamical mechanism is shown, with an IRC/non-IRC ratio that correlates to this relative fraction.
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Affiliation(s)
- Yaicel G Proenza
- Departamento de Química Fundamental, CCEN, Universidade Federal de Pernambuco, 50.740-560, Recife, PE, Brazil
| | - Miguel A F de Souza
- Instituto de Química, CCET, Universidade Federal do Rio Grande do Norte, 59.072-970, Natal, RN, Brazil
| | - Ricardo L Longo
- Departamento de Química Fundamental, CCEN, Universidade Federal de Pernambuco, 50.740-560, Recife, PE, Brazil.
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39
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de Paul N. Nziko V, Scheiner S. Effects of Angular Deformation on the Energetics of the S N2 Reaction. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600712] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
| | - Steve Scheiner
- Department of Chemistry and Biochemistry; Utah State University; 84322-0300 Logan UT USA
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40
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Mahmood A, Longo RL. Structural and relative energy assessments of DFT functionals and the MP2 method to describe the gas phase methylation of nitronates: [R1R2CNO2]− + CH3I. Phys Chem Chem Phys 2016; 18:17062-70. [DOI: 10.1039/c5cp07833d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structures and energetics of CH3I + [R1R2CNO2]− gas phase C- and O-methylation reactions were computed with several functionals and ECP/basis sets and compared to CCSD(T)/CBS.
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Affiliation(s)
- Ayyaz Mahmood
- Departamento de Química Fundamental
- CCEN
- Universidade Federal de Pernambuco
- Cidade Universitária
- Recife
| | - Ricardo L. Longo
- Departamento de Química Fundamental
- CCEN
- Universidade Federal de Pernambuco
- Cidade Universitária
- Recife
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41
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Pabis A, Paluch P, Szala J, Paneth P. A DFT Study of the Kinetic Isotope Effects on the Competing SN2 and E2 Reactions between Hypochlorite Anion and Ethyl Chloride. J Chem Theory Comput 2015; 5:33-6. [PMID: 26609818 DOI: 10.1021/ct800412h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Kinetic isotope effects (KIEs) on the two alternative reactions, SN2 and E2, between hypochlorite anion and ethyl chloride in water have been studied theoretically using B3LYP and M06-2X functionals. It has been found that the latter one yields more correct geometries and energetics. Although, in the qualitative sense, KIEs obtained using both DFT functionals are in agreement, interpretation of some of them, like (18)O-KIE in the present case, leads to different mechanistic conclusions.
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Affiliation(s)
- Anna Pabis
- Faculty of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
| | - Piotr Paluch
- Faculty of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
| | - Joanna Szala
- Faculty of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
| | - Piotr Paneth
- Faculty of Chemistry, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz, Poland
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42
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Swart M, Solà M, Bickelhaupt FM. Density Functional Calculations of E2 and SN2 Reactions: Effects of the Choice of Method, Algorithm, and Numerical Accuracy. J Chem Theory Comput 2015; 6:3145-52. [PMID: 26616777 DOI: 10.1021/ct100454c] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Herein we provide a detailed account on how the potential energy surfaces of the E2 and SN2 reactions of X(-) + CH3CH2X (X = F, Cl) depend on various methodological and technical choices in density functional calculations. We cover a choice of density functionals (OLYP, various M06-types, and the new SSB-D), basis sets (up to quintuple- and quadruple-ζ for Gaussian- and Slater-type orbitals, respectively, plus polarization and diffuse functions), and other aspects of the computations (among others: nonrelativistic versus zeroth-order regular approximation relativistic; numerical integration accuracy; all-electron versus frozen core; self-consistent field (SCF) versus post-SCF). The program codes ADF and NWChem are used for calculations with Slater- and Gaussian-type basis sets, respectively. The fluoride systems (X = F) appear to not only depend extremely sensitively on the basis set size (especially the presence of diffuse functions) but also on other technical settings, especially in the case of hybrid meta-generalized gradient approximation functionals. This work complements a recent contribution (Y. Zhao, D. G. Truhlar, J. Chem. Theory Comput. 2010, 6, 1104) and provides recommendations for density functionals, basis sets, and technical settings.
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Affiliation(s)
- Marcel Swart
- Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, E-17071 Girona, Spain, Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, E-08010 Barcelona, Spain, and Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands
| | - Miquel Solà
- Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, E-17071 Girona, Spain, Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, E-08010 Barcelona, Spain, and Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands
| | - F Matthias Bickelhaupt
- Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, E-17071 Girona, Spain, Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, E-08010 Barcelona, Spain, and Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands
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Ahmadi AA, Fattahi A. Influence of a β-OH substituent on SN2 reactions of fluoroethane: Intramolecular hydrogen bonding catalysis or inhibition? A theoretical study. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2015.05.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Mahmood A, Teixeira ES, Longo RL. Understanding the Reactivity and Regioselectivity of Methylation of Nitronates [R(1)R(2)CNO2](-) by CH3I in the Gas Phase. J Org Chem 2015; 80:8198-205. [PMID: 26181145 DOI: 10.1021/acs.joc.5b01273] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylation of [R(1)R(2)CNO2](-), where R(1) = R(2) = H (1), R(1) = CH3 and R(2) = H (2), R(1) = R(2) = CH3 (3), and R(1) + R(2) = c-(CH2)2 (4), by CH3I was studied by an ab initio MP2/CBS method, RRKM theory, and kinetic simulations. Contrary to a previous proposal for the reaction mechanism, C-methylation is the preferred pathway of thermodynamics and kinetics. This is corroborated by the agreement between the calculated and experimental reactivity trend 4 ≫ 3 > 2 > 1. The regioselectivity toward C-alkylation is explained by the much larger exothermicity of this reaction channel compared to that of O-alkylation. The increase in reactivity with an increase in the crowdedness of the central carbon atom is explained by differences in sp(3) character at this atom and the decrease in the vibrational frequency associated with pyramidalization around this carbon atom.
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Affiliation(s)
- Ayyaz Mahmood
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil
| | - Erico Souza Teixeira
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil
| | - Ricardo L Longo
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50740-560, Brazil
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Pill MF, Schmidt SW, Beyer MK, Clausen-Schaumann H, Kersch A. A density functional theory model of mechanically activated silyl ester hydrolysis. J Chem Phys 2015; 140:044321. [PMID: 25669537 DOI: 10.1063/1.4862827] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutral reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ mol(-1), which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters.
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Affiliation(s)
- Michael F Pill
- Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich, Germany
| | - Sebastian W Schmidt
- Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich, Germany
| | - Martin K Beyer
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel, Germany
| | - Hauke Clausen-Schaumann
- Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich, Germany
| | - Alfred Kersch
- Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich, Germany
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Proenza YG, de Souza MAF, Ventura E, do Monte SA, Longo RL. Assessment of density-functionals for describing the X(-) + CH3ONO2 gas-phase reactions with X = F, OH, CH2CN. Phys Chem Chem Phys 2015; 16:26769-78. [PMID: 25372179 DOI: 10.1039/c4cp03674c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The energetics of the ECO2, SN2@C and SN2@N channels of X(-) + CH3ONO2 (X = F, OH, CH2CN) gas-phase reactions were computed using the CCSD(T)/CBS method. This benchmark extends a previous study with X = OH [M. A. F. de Souza et al., J. Am. Chem. Soc., 2012, 134, 19004] and was used to ascertain the accuracy and robustness of nineteen density-functionals for describing these potential energy profiles (PEP) as well as the kinetic product distributions obtained from RRKM calculations. Assessments were based on the mean unsigned error (MUE), the mean signed error (MSE), the #best : #worst (BW) criterion and the statistical confidence interval (CI) for the MSE. In general, double-hybrid (DH) functionals perform better than the range-separated ones, and both are better than the global-hybrid functionals. Based on the MUE and CI criteria the B2GPPLYP, B2PLYP, M08-SO, BMK, ωB97X-D, CAM-B3LYP, M06, M08-HX, ωB97X and B97-K functionals show the best performance in the description of these PEPs. Within this set, the B2GPPLYP functional is the most accurate and robust. The RRKM results indicate that the DHs are the best for describing the selectivities of these reactions. Compared to CCSD(T), the B2PLYP method has a relative error of only ca. 1% for the selectivity and the accuracy to provide the correct conclusion concerning the nonstatistical behavior of these reactions.
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Affiliation(s)
- Yaicel G Proenza
- Departamento de Química Fundamental, CCEN, Universidade Federal de Pernambuco, Cidade Universitária, Recife, PE 50.740-560, Brazil.
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San LK, Bukovsky EV, Larson BW, Whitaker JB, Deng SHM, Kopidakis N, Rumbles G, Popov AA, Chen YS, Wang XB, Boltalina OV, Strauss SH. A faux hawk fullerene with PCBM-like properties. Chem Sci 2015; 6:1801-1815. [PMID: 29142669 PMCID: PMC5653957 DOI: 10.1039/c4sc02970d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 12/13/2014] [Indexed: 01/27/2023] Open
Abstract
Reaction of C60, C6F5CF2I, and SnH(n-Bu)3 produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C60(CF2C6F5)H (1) and 1,9-C60(cyclo-CF2(2-C6F4)) (2). The highest isolated yield of 1 was 35% based on C60. Depending on the reaction conditions, the relative amounts of 1 and 2 generated in situ were as high as 85% and 71%, respectively, based on HPLC peak integration and summing over all fullerene species present other than unreacted C60. Compound 1 is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 °C but was rapidly converted to 2 upon addition of Sn2(n-Bu)6 at this temperature. In contrast, complete conversion of 1 to 2 occurred within minutes, or hours, at 25 °C in 90/10 (v/v) PhCN/C6D6 by addition of stoichiometric, or sub-stoichiometric, amounts of proton sponge (PS) or cobaltocene (CoCp2). DFT calculations indicate that when 1 is deprotonated, the anion C60(CF2C6F5)- can undergo facile intramolecular SNAr annulation to form 2 with concomitant loss of F-. To our knowledge this is the first observation of a fullerene-cage carbanion acting as an SNAr nucleophile towards an aromatic C-F bond. The gas-phase electron affinity (EA) of 2 was determined to be 2.805(10) eV by low-temperature PES, higher by 0.12(1) eV than the EA of C60 and higher by 0.18(1) eV than the EA of phenyl-C61-butyric acid methyl ester (PCBM). In contrast, the relative E1/2(0/-) values of 2 and C60, -0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the E1/2(0/-) of PCBM is -0.09 V). Time-resolved microwave conductivity charge-carrier yield × mobility values for organic photovoltaic active-layer-type blends of 2 and poly-3-hexylthiophene (P3HT) were comparable to those for equimolar blends of PCBM and P3HT. The structure of solvent-free crystals of 2 was determined by single-crystal X-ray diffraction. The number of nearest-neighbor fullerene-fullerene interactions with centroid···centroid (⊙···⊙) distances of ≤10.34 Å is significantly greater, and the average ⊙···⊙ distance is shorter, for 2 (10 nearest neighbors; ave. ⊙···⊙ distance = 10.09 Å) than for solvent-free crystals of PCBM (7 nearest neighbors; ave. ⊙···⊙ distance = 10.17 Å). Finally, the thermal stability of 2 was found to be far greater than that of PCBM.
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Affiliation(s)
- Long K San
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
| | - Eric V Bukovsky
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
| | - Bryon W Larson
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
- National Renewable Energy Laboratory , Golden , CO 80401 , USA . ;
| | - James B Whitaker
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
| | - S H M Deng
- Physical Sciences Division , Pacific Northwest National Laboratory , MS K8-88, P.O. Box 999 , Richland , WA 99352 , USA .
| | - Nikos Kopidakis
- National Renewable Energy Laboratory , Golden , CO 80401 , USA . ;
| | - Garry Rumbles
- National Renewable Energy Laboratory , Golden , CO 80401 , USA . ;
| | - Alexey A Popov
- Leibniz Institute for Solid State and Materials Research , 01069 Dresden , Germany .
| | - Yu-Sheng Chen
- ChemMatCARS Beamline , University of Chicago Advanced Photon Source , Argonne , IL 60439 , USA .
| | - Xue-Bin Wang
- Physical Sciences Division , Pacific Northwest National Laboratory , MS K8-88, P.O. Box 999 , Richland , WA 99352 , USA .
| | - Olga V Boltalina
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
| | - Steven H Strauss
- Department of Chemistry , Colorado State University , Fort Collins , CO 80523 , USA . ;
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48
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Performance of recent density functionals to discriminate between olefin and nitrogen binding to palladium. Theor Chem Acc 2014. [DOI: 10.1007/s00214-014-1533-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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49
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Zhao X, Geng Z, Yang H, Wang D, Ding W, Liu J. Theoretical investigations on the reaction kinetics of CH3OCl/CD3OCl with chloride ion. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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50
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Wu CH, Galabov B, Wu JIC, Ilieva S, Schleyer PVR, Allen WD. Do π-conjugative effects facilitate SN2 reactions? J Am Chem Soc 2014; 136:3118-26. [PMID: 24450965 DOI: 10.1021/ja4111946] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rigorous quantum chemical investigations of the SN2 identity exchange reactions of methyl, ethyl, propyl, allyl, benzyl, propargyl, and acetonitrile halides (X = F(-), Cl(-)) refute the traditional view that the acceleration of SN2 reactions for substrates with a multiple bond at Cβ (carbon adjacent to the reacting Cα center) is primarily due to π-conjugation in the SN2 transition state (TS). Instead, substrate-nucleophile electrostatic interactions dictate SN2 reaction rate trends. Regardless of the presence or absence of a Cβ multiple bond in the SN2 reactant in a series of analogues, attractive Cβ(δ(+))···X(δ(-)) interactions in the SN2 TS lower net activation barriers (E(b)) and enhance reaction rates, whereas repulsive Cβ(δ(-))···X(δ(-)) interactions increase E(b) barriers and retard SN2 rates. Block-localized wave function (BLW) computations confirm that π-conjugation lowers the net activation barriers of SN2 allyl (1t, coplanar), benzyl, propargyl, and acetonitrile halide identity exchange reactions, but does so to nearly the same extent. Therefore, such orbital interactions cannot account for the large range of E(b) values in these systems.
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Affiliation(s)
- Chia-Hua Wu
- Center for Computational Chemistry and Department of Chemistry, University of Georgia , Athens, Georgia 30602, United States
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