Premium
Mechanism and Kinetics of the Reaction of OH Radicals with Glyoxal and Methylglyoxal: A Quantum Chemistry+CVT/SCT Approach
Author(s) -
Galano Annia,
AlvarezIdaboy J. Raúl,
RuizSantoyo Ma. Esther,
VivierBunge Annik
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400127
Subject(s) - chemistry , glyoxal , methylglyoxal , arrhenius equation , activation energy , hydrogen atom abstraction , potential energy surface , quantum chemistry , computational chemistry , reaction mechanism , kinetics , kinetic energy , thermodynamics , radical , molecule , organic chemistry , physics , enzyme , quantum mechanics , catalysis
A theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from glyoxal and methylglyoxal is presented. Optimum geometries, frequencies, and gradients have been computed at the BHandHLYP/6–311++G(d,p) level of theory for all the stationary points, as well as for 12 additional points along the minimum energy path (MEP). Energies were obtained by single‐point calculations at the above geometries using CCSD(T)/6–311++G(d,p) to produce the potential energy surface. The rate coefficients were calculated for the temperature range 200–500 K by using canonical variational theory (CVT) with small‐curvature tunneling (SCT) corrections. Our analysis suggests a stepwise mechanism, which involves the formation of a reactant complex. The overall agreement between the calculated and experimental kinetic data is very good. This agreement supports the reliability of the Arrhenius parameters of the glyoxal + OH reaction that are proposed in this work for the first time. The Arrhenius expressions that best describe the studied reactions are k 1 =(9.63±0.23)×10 −13 exp[(517±7)/T] and k 2 =(3.93±0.11)×10 −13 exp[(1060±8)/T] cm 3 molecule −1 s −1 for glyoxal and methylglyoxal, respectively.