title: Mechanism and kinetics of the reaction of OH radicals with glyoxal and methylglyoxal: a quantum chemistry + CVT/SCT approach.
abstract: 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 k1 = (9.63 +/- 0.23) x l0(-13)exp[(517 +/- 7)/T] and k2 = (3.93 +/- 0.11) x 10(-13)exp[(1060 +/- 8)/T]cm3 molecule(-1)s(-1) for glyoxal and methylglyoxal, respectively.
authors.affiliation: Instituto Mexicano del Petróleo Eje Central Lázaro Cárdenas 152, 007730, Mexico D. F (México). agalano@imp.mx
authors.forename: Annia
authors.initials: A
authors.lastname: Galano
authors.forename: J Raúl
authors.initials: JR
authors.lastname: Alvarez-Ldaboy
authors.forename: Ma Esther
authors.initials: ME
authors.lastname: Ruiz-Santoyo
authors.forename: Annik
authors.initials: A
authors.lastname: Vivier-Bunge
mesh_terms: D018360:Crystallography, X-Ray; D006037:Glyoxal / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D011765:Pyruvaldehyde / Q000737:chemistry*; D011789:Quantum Theory; D013696:Temperature; D013816:Thermodynamics
chemical_list: D017665:Hydroxyl Radical; D006037:Glyoxal; D011765:Pyruvaldehyde