Theoretical Study on the Kinetics for the Reactions of Heptyl Radicals with Methanol

Ab initio study of the reactions of n -heptyl radicals(1-C 7 H 15 , 2-C 7 H 15 , 3-C 7 H 15 , and 4-C 7 H 15 ) with methanol was conducted over the temperature range of 300–1500 K. Transition states for the reaction channels producing C 7 H 15 OH, CH 3 , C 7 H 15 OCH 3 , H, C 7 H 16 , CH 2 OH and CH 3 O were identified and the geometries of all stationary points were calculated at BB1K/MG3S level of theory. The potential barrier heights of the corresponding transition states were predicted by the CBS-QB3//BB1K and G4//BB1K methods, indicating that the eight H-abstraction channels are more kinetically favorable than the channels where OH transfers from CH 3 OH to C 7 H 15 and where the C 7 H 15 OCH 3 +H products are given. The rate constants of H-abstraction channels were calculated with TST and TST/Eck. Both the forward and reverse rate constants have positive temperature dependence and the tunneling effect is only important at the temperature lower than 700 K. For the reactions of H-atom abstraction from methyl in CH 3 OH by n -heptyl, a reverse and the corresponding forward rate constant are roughly equal. For the reactions of H-atom abstraction from OH in CH 3 OH by n -heptyl, a reverse rate constant is larger by several orders of magnitude than the corresponding forward one.