Atmospheric Oxidation of Methyl Propanoate by the OH radical

Atmospheric oxidation of methyl propanoate (MP) by the OH radical has been performed using density functional theory (BMK, BBIK) and ab initio (MP2, CBS-QB3) calculations. The thermodynamic and kinetic parameters are calculated. Three channels have been discussed. These reactions occur through low energy barriers of 3.2–4.3 kcal/mol. The energy barriers increase in the order α < μ < β at CBS–QB3. However, BMK shows slightly different order. Rate constants and branching ratios reveal that the H-abstraction from Cα is as the dominant reaction over the whole temperature range of 200–300 K, with a competition from Cβ channel at lower temperature. The BB1K data reproduce the available experimental rate constant.