Abstract
In this microreview we revisit the early work in the development of Transition State Theory, paying particular attention to the idea of a dividing surface between reactants and products. The correct location of this surface is defined by the requirement that trajectories not recross it. When that condition is satisfied, the true transition state for the reaction has been found. It is commonly assumed for solution‐phase reactions that if the potential energy terms describing solvent‐solute interactions are small, the true transition state will occur at a geometry close to that for the solute in vacuo. However, we emphasize that when motion of solvent molecules occurs on a time scale similar or longer than that for structural changes in the reacting solute the true transition state may be at an entirely different geometry, and that there is an important inertial component to this phenomenon, which cannot be described on any potential energy surface. We review theories, particularly Grote‐Hynes theory, which have corrected the Transition State Theory rate constant for effects of this kind by computing a reduced transmission coefficient. However, we argue that searching for a true dividing surface with near unit transmission coefficient may sometimes be necessary, especially for the common situation in which the rate‐determining formation of a reactive intermediate is followed by the branching of that intermediate to several products.
Highlights
Presented under the rubric of a microreview, this article is more properly viewed as a hybrid between a review and [a] School of Mathematics, University of Bristol, University Walk, Clifton, Bristol BS8 1TW, country/>United Kingdom a research paper since it contains new material in addition to the expected summary of existing work
Because the rate is calculated as the flux through the transitions states (TSs), any non-reactive trajectory that crosses the TS dividing surface, or reactive trajectory that crosses it more than once will increase the flux through the dividing surface, leading to an overestimate of the rate constant. This means that Transition State Theory (TST) gives us an upper limit on the true rate constant, and that if we found a dividing surface without any recrossing TST would give the exact value of the rate constant
In Variational Transition State Theory (VTST) the dividing surface is variationally optimized to minimize the rate constant, usually by finding the maximum free energy along the reaction path. This surface is properly located in phase space, most of the VTST calculations assume that the TS can be found in configuration space.[16a]. TST and its modern development VTST have been extensively reviewed,[3b,13,17,19,20] but here we will focus on in its application to condensed-phase reactions, its applicability and limitations when working in configuration space, and the potential of including phase space into the methodology
Summary
A research paper since it contains new material in addition to the expected summary of existing work. Rafael Garcia-Meseguer obtained a degree in Chemistry from the University of Valencia in 2010. J. RuizPernía for his Ph.D. in theoretical chemistry and computational modeling in the University of Valencia which he obtained in 2017. RuizPernía for his Ph.D. in theoretical chemistry and computational modeling in the University of Valencia which he obtained in 2017 During this time he collaborated with Damien Laage and J. Hynes in the Ecole Normale Supérieure of Paris After that he moved to the UK where he is currently working as a research associate in the School of Mathematics at the University of Bristol. In 2006 he returned to the UK as director of the Physical Organic Chemistry Centre at Cardiff University. Because phase-space diagrams do not commonly appear in organic chemistry papers, we choose to introduce them first
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
