The mechanism and kinetics for the decomposition of 3-hydroxy-3- methyl-2-butanone and methyl benzoylformate have been studied by using the ab initio RHF/6-31G method. The calculated activation barriers of the two reactions are 251.42kJ/mol and 247.94kJ/mol, respectively, which are in reasonable agreement with the experimental data. The calculated results show that the decomposition of two reactions is a concerted process with hydrogen transferring and bond breaking via a five-membered cyclic transition state and a six-membered cyclic transition state, respectively. The thermal rate constants of the two reactions are obtained by calculating microcanonical probability fluxes through transition state, which are fairly accurate, by comparison with the experimental results.

Key words: AB INITIO CALCULATION, THERMAL DECOMPOSITION, REACTION MECHANISM, TRANSITION STATE