Direct ab initio study on the rate constants of radical C2(A 3Π(u)) + C3H8 reaction.

The mechanism and kinetics of the radical (3)C(2) + C(3)H(8) reaction have been investigated theoretically by direct ab initio kinetics over a wide temperature range. The potential energy surfaces have been constructed at the CCSD(T)/B3//UMP2/B1 levels of theory. The electron transfer was also analyzed by quasi-restricted orbital (QRO) in detail. It was shown that all these channels proceed exclusively via hydrogen abstraction. The overall ICVT/SCT rate constants are in agreement with the available experimental results. The prediction shows that the secondary hydrogen of C(3)H(8) abstraction by (3)C(2) radical is the major pathway at low temperatures (below 700 K), while as the temperature increases, the primary hydrogen of C(3)H(8) abstraction becomes more important and more favorable. A negative temperature dependence of the rate constants for the reaction of (3)C(2) + C(3)H(8) was observed. The three-(k (3)) and four-parameter (k (4)) rate-temperature expressions were also provided within 243-2000 K to facilitate future experimental studies.