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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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Gstir T, Sundelin D, Michaelsen T, Ayasli A, Swaraj D, Judy J, Zappa F, Geppert W, Wester R. Reaction dynamics of the methoxy anion CH 3O - with methyl iodide CH 3I. Faraday Discuss 2024. [PMID: 38770842 DOI: 10.1039/d3fd00164d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Studying larger nucleophiles in bimolecular nucleophilic substitution (SN2) reactions bridges the gap from simple model systems to those relevant to organic chemistry. Therefore, we investigated the reaction dynamics between the methoxy anion (CH3O-) and iodomethane (CH3I) in our crossed-beam setup combined with velocity map imaging at the four collision energies 0.4, 0.7, 1.2, and 1.6 eV. We find the two ionic products I- and CH2I-, which can be attributed to the SN2 and proton transfer channels, respectively. The proton transfer channel progresses in a previously observed fashion from indirect to direct scattering with increasing collision energy. Interestingly, the SN2 channel exhibits direct dynamics already at low collision energies. Both the direct stripping, leading to forward scattering, and the direct rebound mechanism, leading to backward scattering into high angles, are observed.
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Affiliation(s)
- Thomas Gstir
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - David Sundelin
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - Atilay Ayasli
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - Dasarath Swaraj
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - Jerin Judy
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
| | - Wolf Geppert
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, 6020 Innsbruck, Austria.
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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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Liu X, Guo W, Feng H, Pang B, Wu Y. Competition between Elimination and Substitution for Ambident Nucleophiles CN - and Iodoethane Reactions in Gaseous and Aqueous Medium. J Phys Chem A 2023; 127:7373-7382. [PMID: 37639466 DOI: 10.1021/acs.jpca.3c04630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Nucleophilic substitution (SN2) and elimination (E2) reactions between ambident nucleophiles have long been considered as typical reactions in organic chemistry, and exploring the competition between the two reactions is of great importance in chemical synthesis. As a nucleophile, CN- can use its C and N atoms as the reactive centers to undergo E2 and SN2 reactions, but related research is currently limited. This study uses the CCSD(T)/pp/t//MP2/ECP/d electronic structure method to perform detailed investigations on the potential energy profiles for SN2 and E2 reactions between CN- and CH3CH2I in gaseous and aqueous media. The potential energy profiles reveal that the energy barriers for SN2 and E2 reactions with the C atom as the reactive center are consistently lower than those with the N atom, indicating that the C atom has a stronger nucleophilic ability and stronger basicity. Furthermore, the potential energy profiles in both gas and aqueous environments show that the barriers of SN2 reactions are lower than those for E2 reactions with both C and N as the attacking atom. By using the frontier molecular orbital and activation strain models to explain the interesting phenomenon, the transition from the gas phase to solution was investigated, specifically in the gas-microsolvation-water transition. The results show that water molecules reduce the nucleophilicity and basicity of CN-, while strain energy (ΔEstrain) causes a greater increase in the energy barrier for E2 reactions. This study provides new insights and perspectives on the understanding of CN- as a nucleophile in SN2 reactions and serves as theoretical guidance for organic synthesis.
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Affiliation(s)
- Xu Liu
- College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
| | - Wenyu Guo
- College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
| | - Huining Feng
- College of Chemistry, Liaoning University, Shenyang 110036, P. R. 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, 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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7
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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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8
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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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Unexpected steric hindrance failure in the gas phase F - + (CH 3) 3CI S N2 reaction. Nat Commun 2022; 13:4427. [PMID: 35907925 PMCID: PMC9338938 DOI: 10.1038/s41467-022-32191-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 07/18/2022] [Indexed: 11/13/2022] Open
Abstract
Base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) reactions are of significant importance in physical organic chemistry. The textbook example of the retardation of SN2 reactivity by bulky alkyl substitution is widely accepted based on the static analysis of molecular structure and steric environment. However, the direct dynamical evidence of the steric hindrance of SN2 from experiment or theory remains rare. Here, we report an unprecedented full-dimensional (39-dimensional) machine learning-based potential energy surface for the 15-atom F− + (CH3)3CI reaction, facilitating the reliable and efficient reaction dynamics simulations that can reproduce well the experimental outcomes and examine associated atomic-molecular level mechanisms. Moreover, we found surprisingly high “intrinsic” reactivity of SN2 when the E2 pathway is completely blocked, indicating the reaction that intends to proceed via E2 transits to SN2 instead, due to a shared pre-reaction minimum. This finding indicates that the competing factor of E2 but not the steric hindrance determines the small reactivity of SN2 for the F− + (CH3)3CI reaction. Our study provides new insight into the dynamical origin that determines the intrinsic reactivity in gas-phase organic chemistry. Base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) are of significant importance in physical organic chemistry. Here, the authors show that the competing factor of E2 as opposed to steric hindrance determines the low reactivity of SN2 in the F− + (CH3)3CI reaction.
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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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11
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Gallegos M, Costales A, Martín Pendás Á. Does Steric Hindrance Actually Govern the Competition between Bimolecular Substitution and Elimination Reactions? J Phys Chem A 2022; 126:1871-1880. [PMID: 35290051 PMCID: PMC8958592 DOI: 10.1021/acs.jpca.2c00415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bimolecular nucleophilic substitution (SN2) and elimination (E2) reactions are prototypical examples of competing reaction mechanisms, with fundamental implications in modern chemical synthesis. Steric hindrance (SH) is often considered to be one of the dominant factors determining the most favorable reaction out of the SN2 and E2 pathways. However, the picture provided by classical chemical intuition is inevitably grounded on poorly defined bases. In this work, we try to shed light on the aforementioned problem through the analysis and comparison of the evolution of the steric energy (EST), settled within the IQA scheme and experienced along both reaction mechanisms. For such a purpose, the substitution and elimination reactions of a collection of alkyl bromides (R-Br) with the hydroxide anion (OH-) were studied in the gas phase at the M06-2X/aug-cc-pVDZ level of theory. The results show that, generally, EST recovers the appealing trends already anticipated by chemical intuition and organic chemistry, supporting the role that SH is classically claimed to play in the competition between SN2 and E2 reactions.
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Affiliation(s)
- Miguel Gallegos
- Department of Analytical and Physical Chemistry, University of Oviedo, E-33006 Oviedo, Spain
| | - Aurora Costales
- Department of Analytical and Physical Chemistry, University of Oviedo, E-33006 Oviedo, Spain
| | - Ángel Martín Pendás
- Department of Analytical and Physical Chemistry, University of Oviedo, E-33006 Oviedo, Spain
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12
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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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13
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Gallegos M, Costales A, Martín Pendás Á. A real space picture of the role of steric effects in
S
N
2
reactions. J Comput Chem 2022; 43:785-795. [PMID: 35277994 PMCID: PMC9314895 DOI: 10.1002/jcc.26834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/23/2022] [Accepted: 02/24/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Miguel Gallegos
- Department of Analytical and Physical Chemistry University of Oviedo Oviedo Spain
| | - Aurora Costales
- Department of Analytical and Physical Chemistry University of Oviedo Oviedo Spain
| | - Ángel Martín Pendás
- Department of Analytical and Physical Chemistry University of Oviedo Oviedo Spain
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14
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Hansen T, Roozee JC, Bickelhaupt FM, Hamlin TA. How Solvation Influences the S N2 versus E2 Competition. J Org Chem 2021; 87:1805-1813. [PMID: 34932346 PMCID: PMC8822482 DOI: 10.1021/acs.joc.1c02354] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We have quantum chemically
investigated how solvation influences
the competition between the SN2 and E2 pathways of the
model F– + C2H5Cl reaction.
The system is solvated in a stepwise manner by going from the gas
phase, then via microsolvation of one to three explicit solvent molecules,
then last to bulk solvation using relativistic density functional
theory at (COSMO)-ZORA-OLYP/QZ4P. We explain how and why the mechanistic
pathway of the system shifts from E2 in the gas phase to SN2 upon strong solvation of the Lewis base (i.e., nucleophile/protophile).
The E2 pathway is preferred under weak solvation of the system by
dichloromethane, whereas a switch in reactivity from E2 to SN2 is observed under strong solvation by water. Our activation strain
and Kohn–Sham molecular orbital analyses reveal that solvation
of the Lewis base has a significant impact on the strength of the
Lewis base. We show how strong solvation furnishes a weaker Lewis
base that is unable to overcome the high characteristic distortivity
associated with the E2 pathway, and thus the SN2 pathway
becomes viable.
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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
| | - Jasper C Roozee
- 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
| | - 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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15
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Meyer J, Tajti V, Carrascosa E, Győri T, Stei M, Michaelsen T, Bastian B, Czakó G, Wester R. Atomistic dynamics of elimination and nucleophilic substitution disentangled for the F - + CH 3CH 2Cl reaction. Nat Chem 2021; 13:977-981. [PMID: 34373599 PMCID: PMC7611763 DOI: 10.1038/s41557-021-00753-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 06/15/2021] [Indexed: 02/08/2023]
Abstract
Chemical reaction dynamics are studied to monitor and understand the concerted motion of several atoms while they rearrange from reactants to products. When the number of atoms involved increases, the number of pathways, transition states and product channels also increases and rapidly presents a challenge to experiment and theory. Here we disentangle the dynamics of the competition between bimolecular nucleophilic substitution (SN2) and base-induced elimination (E2) in the polyatomic reaction F- + CH3CH2Cl. We find quantitative agreement for the energy- and angle-differential reactive scattering cross-sections between ion-imaging experiments and quasi-classical trajectory simulations on a 21-dimensional potential energy hypersurface. The anti-E2 pathway is most important, but the SN2 pathway becomes more relevant as the collision energy is increased. In both cases the reaction is dominated by direct dynamics. Our study presents atomic-level dynamics of a major benchmark reaction in physical organic chemistry, thereby pushing the number of atoms for detailed reaction dynamics studies to a size that allows applications in many areas of complex chemical networks and environments.
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Affiliation(s)
- Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria
| | - Viktor Tajti
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Eduardo Carrascosa
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tibor Győri
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Martin Stei
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tim Michaelsen
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria
| | - Björn Bastian
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary,
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Univerisität Innsbruck Technikerstraße 25, 6020 Innsbruck, Austria,
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16
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Vermeeren P, Hamlin TA, Bickelhaupt FM. Chemical reactivity from an activation strain perspective. Chem Commun (Camb) 2021; 57:5880-5896. [PMID: 34075969 PMCID: PMC8204247 DOI: 10.1039/d1cc02042k] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 05/25/2021] [Indexed: 12/14/2022]
Abstract
Chemical reactions are ubiquitous in the universe, they are at the core of life, and they are essential for industrial processes. The drive for a deep understanding of how something occurs, in this case, the mechanism of a chemical reaction and the factors controlling its reactivity, is intrinsically valuable and an innate quality of humans. The level of insight and degree of understanding afforded by computational chemistry cannot be understated. The activation strain model is one of the most powerful tools in our arsenal to obtain unparalleled insight into reactivity. The relative energy of interacting reactants is evaluated along a reaction energy profile and related to the rigidity of the reactants' molecular structure and the strength of the stabilizing interactions between the deformed reactants: ΔE(ζ) = ΔEstrain(ζ) + ΔEint(ζ). Owing to the connectedness between the activation strain model and Kohn-Sham molecular orbital theory, one is able to obtain a causal relationship between both the sterics and electronics of the reactants and their mutual reactivity. Only when this is accomplished one can eclipse the phenomenological explanations that are commonplace in the literature and textbooks and begin to rationally tune and optimize chemical transformations. We showcase how the activation strain model is the ideal tool to elucidate fundamental organic reactions, the activation of small molecules by metallylenes, and the cycloaddition reactivity of cyclic diene- and dipolarophiles.
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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.
| | - 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. and Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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17
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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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18
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Wester R. Fifty years of nucleophilic substitution in the gas phase. MASS SPECTROMETRY REVIEWS 2021; 41:627-644. [PMID: 34060119 PMCID: PMC9291629 DOI: 10.1002/mas.21705] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/05/2021] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
Bimolecular nucleophilic substitution ( S N 2 ) reactions have become a model system for the investigation of structure-reactivity relationships, stereochemistry, solvent influences, and detailed atomistic dynamics. In this review, the progress during five decades of experimental and theoretical research on gas phase S N 2 reactions is discussed. Many advancements of the employed methods have led to a tremendous increase in our understanding of the properties and the dynamics of these reactions. For reactions involving six atoms a quantitative agreement of the differential reactive scattering cross sections has already been achieved, in the future it is expected that even larger polyatomic reactions systems become tractable. Furthermore, studies with higher precision, improved reactant control, and a more accurate theoretical treatment of quantum effects are envisioned.
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Affiliation(s)
- Roland Wester
- Institut für Ionenphysik und Angewandte PhysikUniversität InnsbruckTechnikerstraße 256020 InnsbruckAustria
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19
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Vermeeren P, Hansen T, Jansen P, Swart M, Hamlin TA, Bickelhaupt FM. A Unified Framework for Understanding Nucleophilicity and Protophilicity in the S N 2/E2 Competition. Chemistry 2020; 26:15538-15548. [PMID: 32866336 PMCID: PMC7756690 DOI: 10.1002/chem.202003831] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Indexed: 11/11/2022]
Abstract
The concepts of nucleophilicity and protophilicity are fundamental and ubiquitous in chemistry. A case in point is bimolecular nucleophilic substitution (SN 2) and base-induced elimination (E2). A Lewis base acting as a strong nucleophile is needed for SN 2 reactions, whereas a Lewis base acting as a strong protophile (i.e., base) is required for E2 reactions. A complicating factor is, however, the fact that a good nucleophile is often a strong protophile. Nevertheless, a sound, physical model that explains, in a transparent manner, when an electron-rich Lewis base acts as a protophile or a nucleophile, which is not just phenomenological, is currently lacking in the literature. To address this fundamental question, the potential energy surfaces of the SN 2 and E2 reactions of X- +C2 H5 Y model systems with X, Y = F, Cl, Br, I, and At, are explored by using relativistic density functional theory at ZORA-OLYP/TZ2P. These explorations have yielded a consistent overview of reactivity trends over a wide range in reactivity and pathways. Activation strain analyses of these reactions reveal the factors that determine the shape of the potential energy surfaces and hence govern the propensity of the Lewis base to act as a nucleophile or protophile. The concepts of "characteristic distortivity" and "transition state acidity" of a reaction are introduced, which have the potential to enable chemists to better understand and design reactions for synthesis.
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Affiliation(s)
- Pascal Vermeeren
- Department of Theoretical ChemistryAmsterdam Institute of, Molecular and Life Sciences (AIMMS)Amsterdam Center for Multiscale, Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081HVAmsterdamThe Netherlands
| | - Thomas Hansen
- Department of Theoretical ChemistryAmsterdam Institute of, Molecular and Life Sciences (AIMMS)Amsterdam Center for Multiscale, Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081HVAmsterdamThe Netherlands
- Leiden Institute of ChemistryLeiden UniversityEinsteinweg 55, 2333CCLeidenThe Netherlands
| | - Paul Jansen
- Department of Theoretical ChemistryAmsterdam Institute of, Molecular and Life Sciences (AIMMS)Amsterdam Center for Multiscale, Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081HVAmsterdamThe Netherlands
- Laboratory of Physical ChemistryETH ZurichVladimir-Prelog-Weg 28093ZurichSwitzerland
| | - Marcel Swart
- ICREAPg. Lluís Companys 2308010BarcelonaSpain
- IQCC & Dept. QuímicaUniversitat de GironaCampus Montilivi (Ciències)17003GironaSpain
| | - Trevor A. Hamlin
- Department of Theoretical ChemistryAmsterdam Institute of, Molecular and Life Sciences (AIMMS)Amsterdam Center for Multiscale, Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081HVAmsterdamThe Netherlands
| | - F. Matthias Bickelhaupt
- Department of Theoretical ChemistryAmsterdam Institute of, Molecular and Life Sciences (AIMMS)Amsterdam Center for Multiscale, Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081HVAmsterdamThe Netherlands
- Institute for Molecules and MaterialsRadboud UniversityHeyendaalseweg 1356525AJNijmegenThe Netherlands
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20
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Abstract
Nonstatistical dynamics is important for many chemical reactions. The Rice-Ramsperger-Kassel-Marcus (RRKM) theory of unimolecular kinetics assumes a reactant molecule maintains a statistical microcanonical ensemble of vibrational states during its dissociation so that its unimolecular dynamics are time independent. Such dynamics results when the reactant's atomic motion is chaotic or irregular. Intrinsic non-RRKM dynamics occurs when part of the reactant's phase space consists of quasiperiodic/regular motion and a bottleneck exists, so that the unimolecular rate constant is time dependent. Nonrandom excitation of a molecule may result in short-time apparent non-RRKM dynamics. For rotational activation, the 2J + 1 K levels for a particular J may be highly mixed, making K an active degree of freedom, or K may be a good quantum number and an adiabatic degree of freedom. Nonstatistical dynamics is often important for bimolecular reactions and their intermediates and for product-energy partitioning of bimolecular and unimolecular reactions. Post–transition state dynamics is often highly complex and nonstatistical.
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Affiliation(s)
- Bhumika Jayee
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
| | - William L. Hase
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
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21
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Bastian B, Michaelsen T, Li L, Ončák M, Meyer J, Zhang DH, Wester R. Imaging Reaction Dynamics of F -(H 2O) and Cl -(H 2O) with CH 3I. J Phys Chem A 2020; 124:1929-1939. [PMID: 32050071 PMCID: PMC7197043 DOI: 10.1021/acs.jpca.0c00098] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The
dynamics of microhydrated nucleophilic substitution reactions
have been studied using crossed beam velocity map imaging experiments
and quasiclassical trajectory simulations at different collision energies
between 0.3 and 2.6 eV. For F–(H2O) reacting
with CH3I, a small fraction of hydrated product ions I–(H2O) is observed at low collision energies.
This product, as well as the dominant I–, is formed
predominantly through indirect reaction mechanisms. In contrast, a
much smaller indirect fraction is determined for the unsolvated reaction.
At the largest studied collision energies, the solvated reaction is
found to also occur via a direct rebound mechanism. The measured product
angular distributions exhibit an overall good agreement with the simulated
angular distributions. Besides nucleophilic substitution, also ligand
exchange reactions forming F–(CH3I) and,
at high collision energies, proton transfer reactions are detected.
The differential scattering images reveal that the Cl–(H2O) + CH3I reaction also proceeds predominantly
via indirect reaction mechanisms.
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Affiliation(s)
- Björn Bastian
- 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
| | - Lulu Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Jennifer Meyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Dong H Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - 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 L, Fu B, Yang X, Zhang DH. A global ab initio potential energy surface and dynamics of the proton-transfer reaction: OH− + D2 → HOD + D−. Phys Chem Chem Phys 2020; 22:8203-8211. [DOI: 10.1039/d0cp00107d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction mechanisms of OH− + D2 → HOD + D− were first revealed by theory, based on an accurate full-dimensional PES.
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Affiliation(s)
- Lulu Li
- Department of Chemical Physics
- University of Science and Technology of China
- Hefei 230026
- China
- State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry
| | - Bina Fu
- State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry
- Dalian Institute of Chemical Physics
- Chinese Academy of Sciences
- Dalian 116023
- China
| | - Xueming Yang
- Department of Chemical Physics
- University of Science and Technology of China
- Hefei 230026
- China
- State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry
| | - Dong H. Zhang
- Department of Chemical Physics
- University of Science and Technology of China
- Hefei 230026
- China
- State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry
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23
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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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24
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Nucleophilic substitution vs elimination reaction of bisulfide ions with substituted methanes: exploration of chiral selectivity by stereodirectional first-principles dynamics and transition state theory. J Mol Model 2019; 25:227. [PMID: 31317347 DOI: 10.1007/s00894-019-4126-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/07/2019] [Indexed: 10/26/2022]
Abstract
Control of molecular orientation is emerging as crucial for the characterization of the stereodynamics of kinetics processes beyond structural stereochemistry. The special role played in chiral discrimination phenomena has been particularly emphasized by Aquilanti and collaborators after their extensive probes of experimental control of molecular alignment and orientation. In this work, the manifestation of the Aquilanti mechanism has been demonstrated for the first time in first-principles molecular dynamics simulations: stationary points characterized on potential energy surfaces have been calculated for the study of chemical reactions occurring between the bisulfide anion HS- and oriented prototypical chiral molecules CHFXY (where X = CH3 or CN and Y = Cl or I). The important reaction channels are those corresponding to bimolecular nucleophilic substitution (SN2) and to bimolecular elimination (E2): their relative role has been assessed and alternative pathways due to the mirror forms of the oriented chiral molecule are revealed by the different reactivity of the two enantiomers of CHFCNI in SN2 reaction.
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25
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Pratihar S, Nicola Barbosa Muniz MC, Ma X, Borges I, Hase WL. Pronounced changes in atomistic mechanisms for the Cl - + CH 3I S N2 reaction with increasing collision energy. Phys Chem Chem Phys 2019; 21:2039-2045. [PMID: 30633280 DOI: 10.1039/c8cp06198j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In a previous direct dynamics simulation of the Cl- + CH3I → ClCH3 + I- SN2 reaction, predominantly indirect and direct reaction was found at collision energies Erel of 0.20 and 0.39 eV, respectively. For the work presented here, these simulations were extended by studying the reaction dynamics from Erel of 0.15 to 0.40 eV in 0.05 eV intervals. A transition from a predominantly indirect to direct reaction is found for Erel of 0.27-0.28 eV, a finding consistent with experiment. The simulation results corroborate the understanding that in experiments indirect reaction is characterized by small product translational energies and isotropic scattering, while direct reaction has higher translational energies and anisotropic scattering. The traditional statistical theoretical model for the Cl- + CH3I SN2 reaction assumes the Cl--CH3I pre-reaction complex (A) is formed, followed by barrier crossing, and then formation of the ClCH3-I- post-reaction complex (B). This mechanism is seen in the dynamics, but the complete atomistic dynamics are much more complex. Atomistic SN2 mechanisms contain A and B, but other dynamical events consisting of barrier recrossing (br) and the roundabout (Ra), in which the CH3-moiety rotates around the heavy I-atom, are also observed. The two most important mechanisms are only formation of A and Ra + A. The simulation results are compared with simulations and experiments for Cl- + CH3Cl, Cl- + CH3Br, F- + CH3I, and OH- + CH3I.
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Affiliation(s)
- Subha Pratihar
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
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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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