Discerning torquoselectivity in a series of cyclobutene ring-opening reactions using quantum theory of atoms in molecules and stress tensor


This study aims to investigate the phenomenon of torquoselectivity through four thermal cyclobutenes ring-opening reactions including 1-chlorocyclobut-1-ene (Reaction 1), 3-chloro-4-methylcyclobut-1-ene (Reaction 2), 3-methoxy-4-methylcyclobut-1-ene (Reaction 3), and finally 3-chloro-4-methoxycyclobut-1-ene (Reaction 4). Despite the limitation of conventional methods in which just considers activation energies within transition state theory, this research focuses on the nature of the chemical bond, electronic reorganization, and predicting either non-competitive or competitive reactions within quantum theory of atoms in molecules (QTAIM) and stress tensor frameworks. Various theoretical analyses for these reactions such as metallicity ξ(rb), ellipticity ε, total local energy density H(rb), stress tensor polarizability ℙσ, stress tensor eigenvalue λ3σ, bond-path length, and path lengths H display differently for non-competitive and competitive reactions as well as for the conrotatory preferences either it is the transition state outward conrotatory (TSOC) or transition state inward conrotatory (TSIC) directions by presenting degeneracy or non-degeneracy in their results. Results illustrate that the preference of TSOC or TSIC of these thermal ring-opening reactions could obtain from path lengths H of the ring-opening bonds, where the longer one apparently predicts the preference. In addition, examinations indicate that Reaction 1 is competitive and Reactions (2–4) are non-competitive reactions with TSOC, TSOC, and TSIC preference directions respectively. The concordant results of stress tensor and QTAIM scalar and vectors with experimental results provide a better understanding of all reactions mechanism.


National Key Research and DevelopmentProgram of China, Grant/Award Number:2019YFC1907805 The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.


bond critical point, cyclobutene, QTAIM, ring-opening reaction, stress tensor, torquoselectivity


Momen, R., Azizi, A., Morales-Bayuelo, A., Pazhoohesh, M., Ji, X. (2021) International Journal of Quantum Chemistry, e26826.


Research Institute

Institute of Energy and Sustainable Development (IESD)