Atmospheric reaction of OH radicals with 2-methyl-3-buten-2-ol (MBO): Quantum chemical investigation on the reaction mechanism

Predictive Combustion Kinetics of OH Radical Reactions with a C5 Unsaturated Alcohol: The Competitive H-Abstraction and OH-Addition Reactions of 2-Methyl-3-buten-2-ol

2-Methyl-3-buten-2-ol (MBO232) is a potential biofuel and renewable fuel additive. In a combustion environment, the consumption of MBO232 is mainly through the reaction with a OH radical, one of the most important oxidants. Here, we predict the intricate reactions of MBO232 and OH radicals under a broad range of combustion conditions, that is, 230-2500 K and 0.01-1000 atm. The potential energy surfaces of H-abstraction and OH-addition have been investigated at the CCSD(T)/CBS//M06-2X/def2-TZVP level, and the rate constants were calculated via Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) theory. The decomposition reactions of the critical intermediates from the OH-addition reactions have also been studied. Our results show that OH-addition reactions are dominant below 850 K, while H-abstraction reactions, especially the channel-abstracting H atoms from the methyl groups, are more competitive at higher temperatures. We found that it is necessary to discriminate H atoms attached to the same C atom, as their abstraction rates can differ by up to 1 order of magnitude. The calculated results show good agreement with the reported experimental data. We have provided the modified Arrhenius expressions for rate constants of the dominant channels. The kinetic data determined in this work are of much value for constructing the combustion models of MBO232 and understanding the combustion kinetics and mechanism of other unsaturated alcohols.

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

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).