Reaction kinetics of hydrogen addition reactions to methyl butenoate

To investigate the kinetics of hydrogen addition reactions of unsaturated methyl esters, we selected two representative molecules that are isomers with C=C double bonds at different locations, i.e. methyl 2-butenoate and methyl 3-butenoate for study. An appropriate quantum chemical method was determined to compute the potential energy surfaces. The high-pressure limit rate constants were computed by applying multi-structural canonical variational transition state theory including tunneling by the multi-dimensional small-curvature tunneling approximation. The master equation analysis was followed to study the pressure-dependence of the rate constants of H addition and the subsequent dissociation reactions. The results show that it is easier for the H atom to add to the C=C than to the C=O bond because of the lower barrier heights, and the hydrogen addition reactions are faster for both methyl 2-butenoate and methyl 3-butenoate, except that the hydrogen abstraction is dominant at above 1700 K for methyl 2-butenoate. Using our computed rate constants, the prediction for methyl propanoate mole fraction agreed better with experimental data of methyl 2-butenoate combustion.