This work reports a systematic ab initio and chemical kinetic study of the rate constants for hydrogen atom abstraction reactions by hydroxyl radical (OH) on typical isomers of unsaturated C6 methyl esters at the CBS/QB3 level of theory. The high-pressure limit rate constants at different reaction sites for all the methyl esters in the temperature range from 500 to 2000 K are calculated via transition-state theory with the Wigner method for quantum tunneling effect and fitted to the modified three parameters Arrhenius expression using least-squares regression. Further, a branching ratio analysis for each reaction site has been performed. (C) 2016 Elsevier B.V. All rights reserved.