Study of antiradical mechanisms with dihydroxybenzenes using reaction force and reaction electronic flux

Abstract

Phenolic compounds represent an important category of antioxidants because they help inhibit the oxidation process of organic compounds, while also acting as antiradicals in many biological processes. In this work, we analyze the transfer mechanisms for a set of catechols and resorcinols of a single electron, proton and hydrogen, with the radical peroxyl (˙OOH) and with different electron withdrawing and donating groups as substituents. By using the M05-2X exchange correlation functional within the Density Functional Theory framework combined with the 6-311++G(d,p) basis set, we were able to compute the Gibbs free energies for all mechanisms and compounds. According to the thermodynamic results, the hydrogen atom transfer mechanism was the most favorable. Therefore, this mechanism with substituents -CH and -COH in catechol and resorcinol was analyzed, using the reaction force and reaction electronic flux to characterize the structural and electronic changes that take place during the reaction. Our results show that electron donating groups favor electronic changes along the reaction path, increasing the spontaneity of the hydrogen atom transfer mechanism.

Comparison of classical reaction paths and tunneling paths studied with the semiclassical instanton theory

“…The reaction force analysis is an interpretation to distinguish between structural and electronic effects during the course of a chemical reaction 108 . This can be achieved by dividing the reaction into three regions which are separated at the extremal points of the reaction force: In the region from the reactant structure to ξ 1 structural and conformational changes cause an increase of potential energy.…”

“…In the region from ξ 2 to the product structure, the relaxation of the molecular structure leads to a release of potential energy. The structural and electronic contributions to the activation barrier can be quantized by W 1 and W 2 , and the structural and electronic contributions to the release of energy after passing the transition state can be quantized by W 3 and W 4 , respectively: 108,109…”

Interacting Quantum Atoms Analysis of the Reaction Force: A Tool to Analyze Driving and Retarding Forces in Chemical Reactions

“…[33] In this sense, F x ð Þ has been successfully used to analyse reaction mechanisms of different kinds of processes that range from proton transfer to cycloadditions to complex catalytic processes. [34][35][36][37][38][39][40][41][42][43][44] Figure 1. Generic potential energy (green) and reaction force profiles (blue).…”

Mechanism for Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

“…[48][49][50][51] Collectively, these properties represent a powerful toolkit for analyzing chemical reaction mechanisms and has been demonstrated in numerous studies. [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] The reaction force constant particularly has proven useful as an indicator of the synchronous/asynchronous nature of bond breaking/formation, it has been applied extensively to study synchronicity in Diels-Alder reactions. [72,73] Additionally, a recent method developed by Piotr Ordon and coworkers called the bond fragility spectrum aims to analyze the sequence of bond breaking/formation for a reaction by investigating the derivative of properties based on the molecular Hessian.…”