PM3 study of the effects of Ã¯ÂÂ¡-methylation on the gas-phase kinetics of thermal decomposition of ethyl acetatesAuthor(s): I.A.Adejoro
The effects of ï¡-methylation on the gas-phase reaction kinetics andmechanism of the pyrolysis of ethyl acetates was studied theoretically at semiempirical PM3 level.All the calculations showed that the thermal decomposition of these alkyl acetates is a concerted asynchronous process via a six-membered cyclic transition state. The overall result of the calculations shows that ï¡-methyl substitution has a steric releasing effect in the transition state, hence it is rate enhancing. Also it is found that rate enhancement due to C4-O1 bond stretching in the formation of the T.S. is more significant as a rate determinant than the acidic nature of the ï¢ hydrogen eliminated. The first order rate coefficients and computed activation parameters predicted by PM3 method are in good agreement with the experimental results for the series studied.