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Saha PK, Mallick A, Turley AT, Bismillah AN, Danos A, Monkman AP, Avestro AJ, Yufit DS, McGonigal PR. Rupturing aromaticity by periphery overcrowding. Nat Chem 2023; 15:516-525. [PMID: 36879076 PMCID: PMC10070187 DOI: 10.1038/s41557-023-01149-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 01/26/2023] [Indexed: 03/08/2023]
Abstract
The balance between strain relief and aromatic stabilization dictates the form and function of non-planar π-aromatics. Overcrowded systems are known to undergo geometric deformations, but the energetically favourable π-electron delocalization of their aromatic ring(s) is typically preserved. In this study we incremented the strain energy of an aromatic system beyond its aromatic stabilization energy, causing it to rearrange and its aromaticity to be ruptured. We noted that increasing the steric bulk around the periphery of π-extended tropylium rings leads them to deviate from planarity to form contorted conformations in which aromatic stabilization and strain are close in energy. Under increasing strain, the aromatic π-electron delocalization of the system is broken, leading to the formation of a non-aromatic, bicyclic analogue referred to as 'Dewar tropylium'. The aromatic and non-aromatic isomers have been found to exist in rapid equilibrium with one another. This investigation demarcates the extent of steric deformation tolerated by an aromatic carbocycle and thus provides direct experimental insights into the fundamental nature of aromaticity.
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Affiliation(s)
| | | | | | | | - Andrew Danos
- Department of Physics, Durham University, Durham, UK
| | | | | | | | - Paul R McGonigal
- Department of Chemistry, Durham University, Durham, UK.
- Department of Chemistry, University of York, York, UK.
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Rodionova EV, Tomilin OB, Fomina LV. Modeling (Prediction) of the Structure of Possible Transition States of Aromatic Hydrocarbons. RUSSIAN JOURNAL OF ORGANIC CHEMISTRY 2021. [DOI: 10.1134/s1070428021020019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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3
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Moberg C. Symmetry as a Tool for Solving Chemical Problems. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Christina Moberg
- Department of Chemistry, Organic Chemistry, KTH Royal Institute of Technology, SE 100 44 Stockholm, Sweden
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Nohira H, Nohira T. Revisiting the von Neumann–Wigner noncrossing rule and validity of a dynamic correlation diagram method. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2019. [DOI: 10.1142/s0219633619500135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The noncrossing rule for potential energy surfaces can be applied only, as originally postulated by von Neumann and Wigner, to slowly occurring changes; it has, however, over many years, been widely used to rationalize fast chemical reactions. Taking the conversion of Dewar benzene to benzene as an example, we demonstrate a reaction that has a timescale for which crossings are allowed. Since it is now established that elementary chemical reactions proceed over ca. 10–100[Formula: see text]fs, as revealed experimentally by Zewail, the noncrossing rule cannot any longer be said to be valid for most chemical reactions. We further demonstrate that the mechanism of the chemiluminescent conversion of Dewar benzene to benzene is explained by an electronic state diagram derived using a dynamic correlation diagram method which allows crossings, whereas the reaction is not explained by a conventional approach, applying the noncrossing rule using a static correlation diagram method.
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Affiliation(s)
- Hiroyuki Nohira
- Department of Applied Chemistry, Faculty of Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338–8570, Japan
| | - Toshiyuki Nohira
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
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Jones GO, Krebs ZJ. The trimerization of acetylenes involves a cascade of biradical and pericyclic processes. Org Biomol Chem 2017; 15:8326-8333. [DOI: 10.1039/c7ob01885a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thorough computational studies were performed on mechanisms and energies for the thermal trimerizations of neutral or electron-rich acetylenes used as cross-linkers in organic hard-masks for lithography applications.
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Electron density analysis of bent aromatic molecules: intramolecular interactions in small paracyclophanes. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-1960-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Dračínský M, Möller HM, Exner TE. Conformational Sampling by Ab Initio Molecular Dynamics Simulations Improves NMR Chemical Shift Predictions. J Chem Theory Comput 2013; 9:3806-15. [PMID: 26584127 DOI: 10.1021/ct400282h] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Car-Parrinello molecular dynamics simulations were performed for N-methyl acetamide as a small test system for amide groups in protein backbones, and NMR chemical shifts were calculated based on the generated ensemble. If conformational sampling and explicit solvent molecules are taken into account, excellent agreement between the calculated and experimental chemical shifts is obtained. These results represent a landmark improvement over calculations based on classical molecular dynamics (MD) simulations especially for amide protons, which are predicted too high-field shifted based on the latter ensembles. We were able to show that the better results are caused by the solute-solvents interactions forming shorter hydrogen bonds as well as by the internal degrees of freedom of the solute. Inspired by these results, we propose our approach as a new tool for the validation of force fields due to its power of identifying the structural reasons for discrepancies between the experimental and calculated data.
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Affiliation(s)
- Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences , Flemingovo náměstí 2, 166 10 Prague, Czech Republic.,Department of Chemistry, Durham University , DH1 3LE Durham, United Kingdom
| | - Heiko M Möller
- Department of Chemistry, University of Konstanz , 78457 Konstanz, Germany
| | - Thomas E Exner
- Department of Chemistry, University of Konstanz , 78457 Konstanz, Germany.,Theoretical Medicinal Chemistry and Biophysics, Institute of Pharmacy, Eberhard Karls University Tübingen , Auf der Morgenstelle 8, 72076 Tübingen, Germany
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Janková Š, Schulz J, Hybelbauerová S, Císařová I, Štěpnička P, Kotora M. Synthesis of 1,2,3,4-Tetramethyl- and 1,2,3,4-Tetraethylfluorene through a Dewar Benzene Pathway. European J Org Chem 2012. [DOI: 10.1002/ejoc.201201343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Yao ZK, Yu ZX. Mechanisms of the Thermal Cyclotrimerizations of Fluoro- and Chloroacetylenes: Density Functional Theory Investigation and Intermediate Trapping Experiments. J Am Chem Soc 2011; 133:10864-77. [DOI: 10.1021/ja2021476] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zhong-Ke Yao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Zhi-Xiang Yu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
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Hopf H, Mlynek C, McMahon RJ, Menke JL, Lesarri A, Rosemeyer M, Grabow JU. On the Trimerization of Cyanoacetylene: Mechanism of Formation of Tricyanobenzene Isomers and Laboratory Detection of Their Radio Spectra. Chemistry 2010; 16:14115-23. [DOI: 10.1002/chem.201001648] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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