1
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Zhou Y, Fan W, Tang J, Fang W, Zhou M. Heavy-Atom Tunneling in Ring-Closure Reactions of Beryllium Ozonide Complexes. J Am Chem Soc 2024; 146:26719-26725. [PMID: 39290183 DOI: 10.1021/jacs.4c06137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2024]
Abstract
Quantum mechanical tunneling (QMT) has long been recognized as crucial for understanding chemical reaction mechanisms, particularly in reactions involving light atoms like hydrogen. However, recent findings have expanded this understanding to include heavy-atom tunneling reactions. In this report, we present the observation of two heavy-atom tunneling reactions involving the spontaneous conversions from end-on bonded beryllium ozonide complexes, OBeOOO (A) and BeOBeOOO (C), to their corresponding side-on bonded ozonide isomers, OBe(η2-O3) (B) and BeOBe(η2-O3) (D), respectively, in a cryogenic neon matrix. This discovery is supported by the weak temperature dependence of the rate constants and unusually large 16O/18O kinetic isotope effects. Quantum chemistry calculations reveal extremely low barriers (<1 kcal/mol) for both ring-closure reactions. Additionally, instanton theory calculations on both reactions unveil that the tunneling processes involve the concerted motion of all four oxygen atoms.
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Affiliation(s)
- Yangyu Zhou
- Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
| | - Wenbin Fan
- Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
| | - Jingjing Tang
- Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
| | - Wei Fang
- Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
| | - Mingfei Zhou
- Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
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2
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García de la Concepción J, Corchado JC, Cintas P, Babiano R. Norcaradiene-Cycloheptatriene Equilibrium: A Heavy-Atom Quantum Tunneling Case. J Org Chem 2024; 89:9336-9343. [PMID: 38888485 PMCID: PMC11232008 DOI: 10.1021/acs.joc.4c00464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 05/31/2024] [Accepted: 06/07/2024] [Indexed: 06/20/2024]
Abstract
The equilibrium between norcaradiene and cycloheptatriene, which has captivated chemists for more than half a century, is revisited by state-of-the-art quantum chemical calculations. Our theoretical data significantly deviate from the experimental results (J. Am. Chem. Soc., 1981, 26, 7791-7792), especially at low temperatures, where isomerization is dominated by heavy-atom tunneling. This effect results in an extremely short half-life for norcaradiene, rendering it undetectable. This work sheds light on this equilibrium, updating the kinetic and thermodynamic data while also expanding the repertoire of organic reactions controlled by this exotic quantum effect.
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Affiliation(s)
- Juan García de la Concepción
- Departamento de Química Orgánica e Inorgánica, Facultad de Ciencias, and IACYS-Green Chemistry and Sustainable Development Unit, Universidad de Extremadura, 06006 Badajoz, Spain
| | - José C Corchado
- Departamento de Ingeniería Química y Química Física, Facultad de Ciencias, and ICCAEx, Universidad Extremadura, 06006 Badajoz, Spain
| | - Pedro Cintas
- Departamento de Química Orgánica e Inorgánica, Facultad de Ciencias, and IACYS-Green Chemistry and Sustainable Development Unit, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Reyes Babiano
- Departamento de Química Orgánica e Inorgánica, Facultad de Ciencias, and IACYS-Green Chemistry and Sustainable Development Unit, Universidad de Extremadura, 06006 Badajoz, Spain
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3
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Frenklach A, Amlani H, Kozuch S. Quantum Tunneling Instability in Pericyclic Reactions: The Cheletropic, Coarctate, and Ene Cases. Org Lett 2024; 26:5157-5161. [PMID: 38847371 DOI: 10.1021/acs.orglett.4c01635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Some retro-pericyclic reactions, as a result of their high exothermicity and short trajectories, are the perfect ground for heavy atom tunneling molecular decompositions, also known as "quantum tunneling instability" (QTI). Considering this effect, in our first installment [Frenklach, A.; Amlani, H.; Kozuch, S. Quantum Tunneling Instability in Pericyclic Reactions. J. Am. Chem. Soc. 2024, 146 (17), 11823-11834, DOI: 10.1021/jacs.4c00608], we computed several retro-Diels-Alder reactions, predicting that many studied reactants cannot be isolated. Herein, we will explore the QTI of retro-cheletropic, coarctate, and ene exemplars, where again we hypothesize the impossibility to detect their reactants.
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Affiliation(s)
- Alexander Frenklach
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
| | - Hila Amlani
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
| | - Sebastian Kozuch
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
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4
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Qiu G, Schreiner PR. The Intrinsic Barrier Width and Its Role in Chemical Reactivity. ACS CENTRAL SCIENCE 2023; 9:2129-2137. [PMID: 38033803 PMCID: PMC10683502 DOI: 10.1021/acscentsci.3c00926] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 09/29/2023] [Accepted: 10/12/2023] [Indexed: 12/02/2023]
Abstract
Chemical reactions are in virtually all cases understood and explained on the basis of depicting the molecular potential energy landscape, i.e., the change in atomic positions vs the free-energy change. With such landscapes, the features of the reaction barriers solely determine chemical reactivities. The Marcus dissection of the barrier height (activation energy) on such a potential into the thermodynamically independent (intrinsic) and the thermodynamically dependent (Bell-Evans-Polanyi) contributions successfully models the interplay of reaction rate and driving force. This has led to the well-known and ubiquitously used reactivity paradigm of "kinetic versus thermodynamic control". However, an analogous dissection concept regarding the barrier width is absent. Here we define and outline the concept of intrinsic barrier width and the driving force effect on the barrier width and report experimental as well as theoretical studies to demonstrate their distinct roles. We present the idea of changing the barrier widths of conformational isomerizations of some simple aromatic carboxylic acids as models and use quantum mechanical tunneling (QMT) half-lives as a read-out for these changes because QMT is particularly sensitive to barrier widths. We demonstrate the distinct roles of the intrinsic and the thermodynamic contributions of the barrier width on QMT half-lives. This sheds light on resolving conflicting trends in chemical reactivities where barrier widths are relevant and allows us to draw some important conclusions about the general relevance of barrier widths, their qualitative definition, and the consequences for more complete descriptions of chemical reactions.
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Affiliation(s)
- Guanqi Qiu
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Peter R. Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
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5
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Prado Merini M, Schleif T, Sander W. Heavy-Atom Tunneling in Bicyclo[4.1.0]hepta-2,4,6-trienes. Angew Chem Int Ed Engl 2023; 62:e202309717. [PMID: 37698374 DOI: 10.1002/anie.202309717] [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: 07/08/2023] [Revised: 09/11/2023] [Accepted: 09/12/2023] [Indexed: 09/13/2023]
Abstract
Heavy-atom tunneling limits the lifetime and observability of bicyclo[4.1.0]hepta-2,4,6-triene, a key intermediate in the rearrangement of phenylcarbene. Bicyclo[4.1.0]hepta-2,4,6-triene had been proposed as the primary intermediate of the rearrangement of phenylcarbene, but despite many efforts evaded its characterization even in cryogenic matrices. By introducing fluorine substituents into the ortho-positions of the phenyl ring of phenylcarbene, the highly strained cyclopropene 1,5-difluorobicyclo[4.1.0]hepta-2,4,6-triene becomes stable enough to be characterized in argon matrices. However, even at 3 K this cyclopropene is only metastable and rearranges via heavy-atom tunneling to the corresponding cycloheptatetraene. Calculations suggest that fluorination is necessary to slow down the tunneling rearrangement of the bicycloheptatriene. The parent bicycloheptatriene rapidly rearranges via heavy-atom tunneling and therefore cannot be detected under matrix isolation conditions.
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Affiliation(s)
- Melania Prado Merini
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
| | - Tim Schleif
- Department of Chemistry, Yale University, 225 Prospect St., New Haven, CT 06520, USA
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
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6
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Simkó I, Schran C, Brieuc F, Fábri C, Asvany O, Schlemmer S, Marx D, Császár AG. Quantum Nuclear Delocalization and its Rovibrational Fingerprints. Angew Chem Int Ed Engl 2023; 62:e202306744. [PMID: 37561837 DOI: 10.1002/anie.202306744] [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: 05/15/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/12/2023]
Abstract
Quantum mechanics dictates that nuclei must undergo some delocalization. In this work, emergence of quantum nuclear delocalization and its rovibrational fingerprints are discussed for the case of the van der Waals complexHHe 3 + ${{\rm{HHe}}_3^ + }$ . The equilibrium structure ofHHe 3 + ${{\rm{HHe}}_3^ + }$ is planar and T-shaped, one He atom solvating the quasi-linear He-H+ -He core. The dynamical structure ofHHe 3 + ${{\rm{HHe}}_3^ + }$ , in all of its bound states, is fundamentally different. As revealed by spatial distribution functions and nuclear densities, during the vibrations of the molecule the solvating He is not restricted to be in the plane defined by the instantaneously bentHHe 2 + ${{\rm{HHe}}_2^ + }$ chomophore, but freely orbits the central proton, forming a three-dimensional torus around theHHe 2 + ${{\rm{HHe}}_2^ + }$ chromophore. This quantum delocalization is observed for all vibrational states, the type of vibrational excitation being reflected in the topology of the nodal surfaces in the nuclear densities, showing, for example, that intramolecular bending involves excitation along the circumference of the torus.
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Affiliation(s)
- Irén Simkó
- Laboratory of Molecular Structure and Dynamics, Institute of Chemistry, ELTE Eötvös Loránd University, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
- MTA-ELTE Complex Chemical Systems Research Group, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
- Hevesy György PhD School of Chemistry, ELTE Eötvös Loránd University, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
| | - Christoph Schran
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany
- Present address: Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Fabien Brieuc
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany
- Present address: Laboratoire Matière en Conditions Extrêmes, Université Paris-Saclay, CEA, DAM, DIF, 91297, Arpajon, France
| | - Csaba Fábri
- MTA-ELTE Complex Chemical Systems Research Group, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
| | - Oskar Asvany
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937, Köln, Germany
| | - Stephan Schlemmer
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937, Köln, Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Attila G Császár
- Laboratory of Molecular Structure and Dynamics, Institute of Chemistry, ELTE Eötvös Loránd University, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
- MTA-ELTE Complex Chemical Systems Research Group, H-1117, Budapest, Pázmány Péter sétány 1/A, Hungary
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7
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Madinah R, Rusydi F, Fadilla RN, Khoirunisa V, Boli LSP, Saputro AG, Hassan NH, Ahmad A. First-Principles Study of the Dispersion Effects in the Structures and Keto-Enol Tautomerization of Curcumin. ACS OMEGA 2023; 8:34022-34033. [PMID: 37744805 PMCID: PMC10515353 DOI: 10.1021/acsomega.3c04907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 08/18/2023] [Indexed: 09/26/2023]
Abstract
Noncovalent interactions, such as dispersion, play a significant role in the stability of flexible molecules, such as curcumin. This study revealed the importance of dispersion correction in the structure and keto-enol tautomerization of curcumin, which has rarely been addressed in computational studies. We rigorously constructed all possible unique curcumin conformers in the enol and keto forms within the first-principles framework. Regardless of the different environments, we carefully explained the agreement between the computational geometry (in the gas phase) and the experimental measurement (in the polymorph) by using dispersion correction. The calculation results for the aqueous solution of conformational abundance, thermochemistry, and reaction kinetics support the experimental observations after considering the dispersion correction. The study also suggests a water-catalyzed mechanism for keto-enol tautomerization, where dispersion correction plays a role in decreasing the energy barrier and making the keto form thermochemically and kinetically favorable. Our results could be helpful in future computational studies to find a method for increasing the aqueous solubility of curcumin; hence, the potential of curcumin as a multifunctional medicine can be fully achieved.
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Affiliation(s)
- Roichatul Madinah
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
| | - Febdian Rusydi
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Physics, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
| | - Rizka N. Fadilla
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Precision Engineering, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
| | - Vera Khoirunisa
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Department
of Engineering Physics, Institut Teknologi
Sumatera, Jl. Terusan Ryacudu, Lampung Selatan 35365, Indonesia
| | - Lusia S. P. Boli
- Research
Center for Quantum Engineering Design, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia
- Advanced
Functional Materials Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung 40132, Indonesia
- Physics Study
Program, Faculty of Mathematics and Natural Sciences, Universitas Jendral Soedirman, Purwokerto 53122, Indonesia
| | - Adhitya G. Saputro
- Advanced
Functional Materials Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung 40132, Indonesia
| | - Nur H. Hassan
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
| | - Azizan Ahmad
- Department
of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
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8
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Ma Z, Yan Z, Li X, Chung LW. Quantum Tunneling in Reactions Modulated by External Electric Fields: Reactivity and Selectivity. J Phys Chem Lett 2023; 14:1124-1132. [PMID: 36705472 DOI: 10.1021/acs.jpclett.2c03461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Quantum tunneling and external electric fields (EEFs) can promote some reactions. However, the synergetic effect of an EEF on a tunneling-involving reaction and its temperature-dependence is not very clear. In this study, we extensively investigated how EEFs affect three reactions that involve hydrogen- or (ground- and excited-state) carbon-tunneling using reliable DFT, DLPNO-CCSD(T1), and variational transition-state theory methods. Our study revealed that oriented EEFs can significantly reduce the barrier and corresponding barrier width (and vice versa) through more electrostatic stabilization in transition states. These EEF effects enhance the nontunneling and tunneling-involving rates. Such EEF effects also decrease the crossover temperatures and quantum tunneling contribution, albeit with lower and thinner barriers. Moreover, EEFs can modulate and switch on/off the tunneling-driven 1,2-H migration of hydroxycarbenes under cryogenic conditions. Furthermore, our study predicts for the first time that EEF/tunneling synergy can control the chemo- or site-selectivity of one molecule bearing two similar/same reactive sites.
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Affiliation(s)
- Zhifeng Ma
- Shenzhen Grubbs Institute, Department of Chemistry, and Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen 518055, P. R. China
| | - Zeyin Yan
- Shenzhen Grubbs Institute, Department of Chemistry, and Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen 518055, P. R. China
| | - Xin Li
- Shenzhen Grubbs Institute, Department of Chemistry, and Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen 518055, P. R. China
| | - Lung Wa Chung
- Shenzhen Grubbs Institute, Department of Chemistry, and Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen 518055, P. R. China
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9
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Nunes CM, Doddipatla S, Loureiro GF, Roque JPL, Pereira NAM, Pinho e Melo TMVD, Fausto R. Differential Tunneling-Driven and Vibrationally-Induced Reactivity in Isomeric Benzazirines. Chemistry 2022; 28:e202202306. [PMID: 36066476 PMCID: PMC10092225 DOI: 10.1002/chem.202202306] [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: 07/23/2022] [Indexed: 11/08/2022]
Abstract
Quantum mechanical tunneling of heavy-atoms and vibrational excitation chemistry are unconventional and scarcely explored types of reactivity. Once fully understood, they might bring new avenues to conduct chemical transformations, providing access to a new world of molecules or ways of exquisite reaction control. In this context, we present here the discovery of two isomeric benzazirines exhibiting differential tunneling-driven and vibrationally-induced reactivity, which constitute exceptional results for probing into the nature of these phenomena. The isomeric 6-fluoro- and 2-fluoro-4-hydroxy-2H-benzazirines (3-a and 3'-s) were generated in cryogenic krypton matrices by visible-light irradiation of the corresponding triplet nitrene 3 2-a, which was produced by UV-light irradiation of its azide precursor. The 3'-s was found to be stable under matrix dark conditions, whereas 3-a spontaneously rearranges (τ1/2 ∼64 h at 10 and 20 K) by heavy-atom tunneling to 3 2-a. Near-IR-light irradiation at the first OH stretching overtone frequencies (remote vibrational antenna) of the benzazirines induces the 3'-s ring-expansion reaction to a seven-member cyclic ketenimine, but the 3-a undergoes 2H-azirine ring-opening reaction to triplet nitrene 3 2-a. Computations demonstrate that 3-a and 3'-s have distinct reaction energy profiles, which explain the different experimental results. The spectroscopic direct measurement of the tunneling of 3-a to 3 2-a constitutes a unique example of an observation of a species reacting only by nitrogen tunneling. Moreover, the vibrationally-induced sole activation of the most favorable bond-breaking/bond-forming pathway available for 3-a and 3'-s provides pioneer results regarding the selective nature of such processes.
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Affiliation(s)
- Cláudio M. Nunes
- University of Coimbra, CQC-IMS Department of Chemistry3004-535CoimbraPortugal
| | - Srinivas Doddipatla
- University of Coimbra, CQC-IMS Department of Chemistry3004-535CoimbraPortugal
| | - Gonçalo F. Loureiro
- University of Coimbra, CQC-IMS Department of Chemistry3004-535CoimbraPortugal
| | - José P. L. Roque
- University of Coimbra, CQC-IMS Department of Chemistry3004-535CoimbraPortugal
| | | | | | - Rui Fausto
- University of Coimbra, CQC-IMS Department of Chemistry3004-535CoimbraPortugal
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10
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Nunes CM, Roque JP, Doddipatla S, Wood SA, McMahon RJ, Fausto R. Simultaneous Tunneling Control in Conformer-Specific Reactions. J Am Chem Soc 2022; 144:20866-20874. [PMID: 36321916 PMCID: PMC9776521 DOI: 10.1021/jacs.2c09026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We present here a new example of chemical reactivity governed by quantum tunneling, which also highlights the limitations of the classical theories. The syn and anti conformers of a triplet 2-formylphenylnitrene, generated in a nitrogen matrix, were found to spontaneously rearrange to the corresponding 2,1-benzisoxazole and imino-ketene, respectively. The kinetics of both transformations were measured at 10 and 20 K and found to be temperature-independent, providing clear evidence of concomitant tunneling reactions (heavy-atom and H-atom). Computations confirm the existence of these tunneling reaction pathways. Although the energy barrier between the nitrene conformers is lower than any of the observed reactions, no conformational interconversion was observed. These results demonstrate an unprecedented case of simultaneous tunneling control in conformer-specific reactions of the same chemical species. The product outcome is impossible to be rationalized by the conventional kinetic or thermodynamic control.
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Affiliation(s)
- Cláudio M. Nunes
- University
of Coimbra, CQC-IMS, Department of Chemistry, 3004-535 Coimbra, Portugal,
| | - José P.
L. Roque
- University
of Coimbra, CQC-IMS, Department of Chemistry, 3004-535 Coimbra, Portugal
| | - Srinivas Doddipatla
- University
of Coimbra, CQC-IMS, Department of Chemistry, 3004-535 Coimbra, Portugal
| | - Samuel A. Wood
- Department
of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706-1322, United States
| | - Robert J. McMahon
- Department
of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706-1322, United States
| | - Rui Fausto
- University
of Coimbra, CQC-IMS, Department of Chemistry, 3004-535 Coimbra, Portugal
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11
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Schleif T. Transformations of Strained Three-Membered Rings a Common, Yet Overlooked, Motif in Heavy-Atom Tunneling Reactions. Chemistry 2022; 28:e202201775. [PMID: 35762788 PMCID: PMC9804509 DOI: 10.1002/chem.202201775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Indexed: 01/05/2023]
Abstract
Quantum mechanical tunneling has long been recognized as an important phenomenon when considering transformations dominated by a lightweight hydrogen atom. Tunneling of heavier atoms like carbon, initially dismissed as negligible, has seen a quickly increasing number of computationally predicted and/or experimentally confirmed examples over the last decade, thus highlighting its importance for a wide variety of reactions. However, no common structural motif has been pointed out within these seemingly unconnected examples, strongly limiting the predictability of the impact of heavy-atom tunneling on a given reaction. This Concept article will provide this perspective and showcase how the recognition of the formation and cleavage of three-membered rings as common motif can inform the prediction of and research into heavy-atom tunneling reactions.
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Affiliation(s)
- Tim Schleif
- Lehrstuhl für Organische Chemie IIRuhr-Universität Bochum44780BochumGermany
- Present address: Sterling Chemistry LaboratoryYale UniversityNew HavenCT 06520USA
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12
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Schleif T, Prado Merini M, Henkel S, Sander W. Solvation Effects on Quantum Tunneling Reactions. Acc Chem Res 2022; 55:2180-2190. [PMID: 35730754 DOI: 10.1021/acs.accounts.2c00151] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A decisive factor for obtaining high yields and selectivities in organic synthesis is the choice of the proper solvent. Solvent selection is often guided by the intuitive understanding of transition state-solvent interactions. However, quantum-mechanical tunneling can significantly contribute to chemical reactions, circumventing the transition state and thus depriving chemists of their intuitive handle on the reaction kinetics. In this Account, we aim to provide rationales for the effects of solvation on tunneling reactions derived from experiments performed in cryogenic matrices.The tunneling reactions analyzed here cover a broad range of prototypical organic transformations that are subject to strong solvation effects. Examples are the hydrogen tunneling probability for the cis-trans isomerization of formic acid which is strongly reduced upon formation of hydrogen-bonded complexes and the [1,2]H-shift in methylhydroxycarbene where a change in product selectivity is predicted upon interaction with hydrogen bond acceptors.Not only hydrogen but also heavy atom tunneling can exhibit strong solvent effects. The direction of the nearly degenerate valence tautomerization between benzene oxide and oxepin was found to reverse upon formation of a halogen or hydrogen bond with ICF3 or H2O. But even in the absence of strong noncovalent interactions such as hydrogen or halogen bonding, solvation can have a decisive effect on tunneling as evidenced by the Cope rearrangement of semibullvalenes via heavy-atom tunneling. Can quantum tunneling be catalyzed? The acceleration of the ring expansion of 1H-bicyclo[3.1.0.]-hexa-3,5-dien-2-one by complexation with Lewis acids provides a proof-of-concept for tunneling catalysis.Two concepts are central for the explanation and prediction of solvation effects on tunneling phenomena: a simple approach expands the Born-Oppenheimer approximation by separating nuclear degrees of freedom into intra- and intermolecular degrees. Intermolecular movements represent the slowest motions within molecular aggregates, thus effectively freezing the position of the solvent in relation to the reactant during the tunneling process. Another useful approach is to treat reactants and products by separate single-well potentials, where the intersection represents the transition state. Thus, stabilization of the reactants via solvation should result in an increase in barrier heights and widths which in turn lowers tunneling probabilities. These simple models can predict trends in tunneling kinetics and provide a rational basis for controlling tunneling reactions via solvation.
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Affiliation(s)
- Tim Schleif
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Melania Prado Merini
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Stefan Henkel
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
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13
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Roque JPL, Nunes CM, Fausto R. Matrix Isolation in Heterocyclic Chemistry. HETEROCYCLES 2022. [DOI: 10.1002/9783527832002.ch12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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14
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Fausto R, Ildiz GO, Nunes CM. IR-induced and tunneling reactions in cryogenic matrices: the (incomplete) story of a successful endeavor. Chem Soc Rev 2022; 51:2853-2872. [PMID: 35302145 DOI: 10.1039/d1cs01026c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In this article, IR-induced and tunneling-driven reactions observed in cryogenic matrices are described in a historical perspective, the entangling of the two types of processes being highlighted. The story of this still ongoing fascinating scientific endeavor is presented here following closely our own involvement in the field for more than 30 years, and thus focuses mostly on our work. It is, because of this reason, also an incomplete story. Nevertheless, it considers a large range of examples, from very selective IR-induced conformational isomerizations to IR-induced bond-breaking/bond-forming reactions and successful observations of rare heavy atom tunneling processes. As a whole, this article provides a rather general overview of the major progress achieved in the field.
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Affiliation(s)
- Rui Fausto
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
| | - Gulce O Ildiz
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. .,Department of Physics, Faculty of Sciences and Letters, Istanbul Kultur University, 34158 Bakirkoy, Istanbul, Turkey
| | - Cláudio M Nunes
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
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15
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Mandal N, Das A, Hajra C, Datta A. Stereoelectronic and dynamical effects dictate nitrogen inversion during valence isomerism in benzene imine. Chem Sci 2022; 13:704-712. [PMID: 35173935 PMCID: PMC8769061 DOI: 10.1039/d1sc04855d] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/14/2021] [Indexed: 01/23/2023] Open
Abstract
Non-classical processes such as heavy-atom tunneling and post transition-state dynamics govern stereoselectivity for benzene imine ⇌ 1H-azepine.
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Affiliation(s)
- Nilangshu Mandal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, West Bengal, India
| | - Ankita Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, West Bengal, India
| | - Chandralekha Hajra
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, West Bengal, India
| | - Ayan Datta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, West Bengal, India
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16
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Schleif T, Sander W. Photolysis and thermolysis of (iodomethyl)cyclopropane: Rapid ring opening of cyclopropylcarbinyl via heavy‐atom tunneling? J PHYS ORG CHEM 2021. [DOI: 10.1002/poc.4295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Tim Schleif
- Lehrstuhl für Organische Chemie II Ruhr‐Universität Bochum Bochum Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II Ruhr‐Universität Bochum Bochum Germany
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17
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Henkel S, Merini MP, Mendez-Vega E, Sander W. Lewis acid catalyzed heavy atom tunneling - the case of 1 H-bicyclo[3.1.0]-hexa-3,5-dien-2-one. Chem Sci 2021; 12:11013-11019. [PMID: 34522298 PMCID: PMC8386641 DOI: 10.1039/d1sc02853g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/15/2021] [Indexed: 11/21/2022] Open
Abstract
For many thermal reactions, the effects of catalysis or the influence of solvents on reaction rates can be rationalized by simple transition state models. This is not the case for reactions controlled by quantum tunneling, which do not proceed via transition states, and therefore lack the simple concept of transition state stabilization. 1H-Bicyclo[3.1.0]-hexa-3,5-dien-2-one is a highly strained cyclopropene that rearranges to 4-oxocyclohexa-2,5-dienylidene via heavy-atom tunneling. H2O, CF3I, or BF3 form Lewis acid–base complexes with both reactant and product, and the influence of these intermolecular complexes on the tunneling rates for this rearrangement was studied. The tunneling rate increases by a factor of 11 for the H2O complex, by 23 for the CF3I complex, and is too fast to be measured for the BF3 complex. These observations agree with quantum chemical calculations predicting a decrease in both barrier height and barrier width upon complexation with Lewis acids, resulting in the observed Lewis acid catalysis of the tunneling rearrangement. The ring-opening of a highly strained cyclopropene to a carbene proceeds via heavy-atom tunneling. This rearrangement is accelerated in the presence of H2O, ICF3 or BF3, resulting in a novel Lewis-acid catalyzed tunneling reaction.![]()
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Affiliation(s)
- Stefan Henkel
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum 44801 Bochum Germany
| | - Melania Prado Merini
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum 44801 Bochum Germany
| | - Enrique Mendez-Vega
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum 44801 Bochum Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum 44801 Bochum Germany
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18
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Sokol KR, Magauer T. Total Synthesis of Oxepin and Dihydrooxepin Containing Natural Products. SYNTHESIS-STUTTGART 2021; 53:4187-4202. [PMID: 35001983 PMCID: PMC7612190 DOI: 10.1055/s-0037-1610776] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The construction of oxepin and dihydrooxepin containing natural products represents a challenging task in total synthesis. In the last decades, a variety of synthetic methods have been reported for the installation of these structural motifs. Herein, we provide an overview of synthetic methods and strategies to construct these motifs in the context of natural product synthesis and highlight the key steps of each example.
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Affiliation(s)
- Kevin Rafael Sokol
- Institute of Organic Chemistry and Center for Molecular Biosciences, Leopold-Franzens-University Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Thomas Magauer
- Institute of Organic Chemistry and Center for Molecular Biosciences, Leopold-Franzens-University Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
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19
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Kirshenboim O, Frenklah A, Kozuch S. Switch chemistry at cryogenic conditions: quantum tunnelling under electric fields. Chem Sci 2020; 12:3179-3187. [PMID: 34164085 PMCID: PMC8179409 DOI: 10.1039/d0sc06295b] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 12/15/2020] [Indexed: 12/03/2022] Open
Abstract
While the influence of intramolecular electric fields is a known feature in enzymes, the use of oriented external electric fields (EEF) to enhance or inhibit molecular reactivity is a promising topic still in its infancy. Herein we will explore computationally the effects that EEF can provoke in simple molecules close to the absolute zero, where quantum tunnelling (QT) is the sole mechanistic option. We studied three exemplary systems, each one with different reactivity features and known QT kinetics: π bond-shifting in pentalene, Cope rearrangement in semibullvalene, and cycloreversion of diazabicyclohexadiene. The kinetics of these cases depend both on the field strength and its direction, usually giving subtle but remarkable changes. However, for the cycloreversion, which suffers large changes on the dipole through the reaction, we also observed striking results. Between the effects caused by the EEF on the QT we observed an inversion of the Arrhenius equation, deactivation of the molecular fluxionality, and stabilization or instantaneous decomposition of the system. All these effects may well be achieved, literally, at the flick of a switch.
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Affiliation(s)
- Omer Kirshenboim
- Department of Chemistry, Ben-Gurion University of the Negev Beer-Sheva 841051 Israel
| | - Alexander Frenklah
- Department of Chemistry, Ben-Gurion University of the Negev Beer-Sheva 841051 Israel
| | - Sebastian Kozuch
- Department of Chemistry, Ben-Gurion University of the Negev Beer-Sheva 841051 Israel
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