Reaction mechanism of CH + C(3)H(6): a theoretical study.

A detailed theoretical study is performed at the B3LYP/6-311G(d,p) and G3B3 (single-point) levels as an attempt to explore the reaction mechanism of CH with C(3)H(6). It is shown that the barrierless association of CH with C(3)H(6) forms two energy-rich isomers CH(3)-cCHCHCH(2) (1), and CH(2)CH(2)CHCH(2) (4). Isomers 1 and 4 are predicted to undergo subsequent isomerization and dissociation steps leading to ten dissociation products P(1) (CH(3)-cCHCHCH + H), P(2) (CH(3)-cCCHCH(2) + H), P(3) (cCHCHCH(2) + CH(3)), P(4) (CH(3)CHCCH(2) + H), P(5) (cis-CH(2)CHCHCH(2) + H), P(6) (trans-CH(2)CHCHCH(2) + H), P(7) (C(2)H(4) + C(2)H(3)), P(8) (CH(3)CCH + CH(3)), P(9) (CH(3)CCCH(3) + H) and P(12) (CH(2)CCH(2) + CH(3)), which are thermodynamically and kinetically possible. Among these products, P(5), P(6), and P(7) may be the most favorable products with comparable yields; P(1), P(2), and P(3) may be the much less competitive products, followed by the almost negligible P(4), P(8), P(9), and P(12). Since the isomers and transition states involved in the CH + C(3)H(6) reaction all lie lower than the reactant, the title reaction is expected to be fast, which is consistent with the measured large rate constant in experiment. The present study may lead us to a deep understanding of the CH radical chemistry.