Thermochemistry of Csingle bondO, (CO)single bondO, and (CO)single bondC bond breaking in fatty acid methyl esters

Density functional theory quantum chemical calculations corrected with empirical atomic increments have been used to examine Csingle bondO, (CO)single bondO, and (CO)single bondC bond scission enthalpies in gas-phase fatty acid methyl esters (FAMEs) present in biodiesel derived from rapeseed oil methyl ester and soybean oil methyl ester. Mechanistic information, currently not available elsewhere for these large species, is obtained based on thermochemical considerations and compared to thermochemical considerations reported for methyl butanoate, a small methyl ester sometimes used as a model for FAMEs. These results are compared to previously reported Csingle bondC and Csingle bondH bond scissions in these FAMEs, derived using this same protocol.