Transition structures of chemical reactions in solution through the free energy gradient method

• Grant number: 16/22723-2
• Support Opportunities: Research Grants - Visiting Researcher Grant - Brazil
• Start date: April 17, 2017
• End date: August 16, 2017
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Sylvio Roberto Accioly Canuto
• Grantee: Sylvio Roberto Accioly Canuto
• Visiting researcher: Herbert de Castro Georg
• Visiting researcher institution: Universidade Federal de Goiás (UFG). Instituto de Física, Brazil
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The research project proposes the computational implementation of a method to optimize transition structures for the study of chemical reactions in solution using an atomistic description of the molecular environment of the reaction through computer simulation methods.This method explicitly takes into account the electronic structure of the system of interest (where the reaction occurs) through first principles quantum mechanics methods, while the molecular environment is treated through empirical force fields, that is, within a hybrid methodology called QM / MM. This methodology is an efficient and much less computationally expensive alternative to first principles computer simulations.This hybrid methodology is already used in the groups of both of the researchers involved to optimize minima on the free energy hypersurface of the system (meaning to locate reagents and products). With the implementation of the optimization of transition structures in solution it will be possible to achieve a greater understanding of the mechanisms of reaction, providing a significant advance in the study of chemical reactions.Although very important, the theoretical study of chemical reactions is difficult, even in vacuum, due to the difficulty in locating the transition states, which allow a more complete view of the reaction mechanism. In solution, this study becomes even more complicated due to the need to take into account the molecular environment, which is also not trivial.There are simple approaches that can be employed to model the molecular environment, treating it as a dielectric continuum, where the atomistic detail is neglected. These approaches offer an interesting alternative to simple solutions where the solvent molecules do not interact specifically with the molecules of the system of interest. However, they fail for more complex solutions or where there are specific solute-solvent interactions.Our proposal is to implement a more general method that can be used to attack, in a much more comprehensive way, the study of chemical reactions in solvent, or even in more complex molecular and biomolecular environments. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

VALVERDE, DANILLO; GEORG, HERBERT C.; CANUTO, SYLVIO. Free-Energy Landscape of the S(N)2 Reaction CH3Br + Cl- ? CH3Cl + Br- in Different Liquid Environments. Journal of Physical Chemistry B, v. 126, n. 20, p. 8-pg., 2022-05-26. (14/50983-3, 17/02612-4, 16/22723-2)