Reaction mechanism and kinetic study of the •OH initiated tropospheric oxidation of 3-methyl-2-buten-1-ol: A quantum chemical investigation

Abstract

In this article a theoretical study of mechanism and kinetics of the OH -initiated oxidation reaction of 3-methyl-2-buten-1-ol (MBO-321) is presented. This degradation mechanism of MBO-321 consists of H -abstraction reaction and OH -addition to olefinic bond. In addition, probable product analysis alongwith the mechanism for secondary reactions in presence of O 2 and NO has been investigated. Energetics have been studied at the CCSD(T)/6-311++g(d,p)//MP2 = full/6-31+G(d) level of theory. Thermochemical analysis has been done using CBS-QB3 method starting from the geometry obtained in the MP2 method. All the H -abstraction reactions pass through positive energy barrier except H4 -abstraction channel. OH -addition to the double bond takes place via formation of the pre-reactive complex as these reaction channel pass through negative activation barrier. OH -addition is the predominant reaction pathway for the overall oxidation process. Using TST theory at 1 atm pressure and in the temperature range of 200 K–400 K, the calculated rate constant and lifetime of OH -addition is [Formula: see text] molecule-1 s-1 and 1.88 h, which is consistent with the previous experimental data, [Formula: see text] molecule-1 s-1 and 1.9 h respectively (Imamura et al., Rate coefficients for the gas phase reactions of OH radical with methylbutenols at 298 K, Int J Chem Kinet36:379–385, 2004).