Ab initio and direct dynamics study on the C2H3 + CH3CH2OH reaction

Abstract

ABSTRACTThe mechanism for the C2H3 + CH3CH2OH reaction has been investigated by the CCSD(T)/cc-pVTZ method based on the geometries of stationary points optimised at the B3LYP/6-311++G(d, p) level of theory. Five reaction channels have been identified for the production of C2H4 + CH2CH2OH, C2H4 + CH3CH2O, C2H4 + CH3CHOH, C2H3OH + CH3CH2, and C2H3OCH2CH3 + H (denoted as channels (1)–(5), respectively). The potential barrier heights of the corresponding transition states TSR/P1, TSR/P2, TSR/P3, TSR/P4 and TSR/P5 were predicted to be 12.40, 8.50, 8.11, 38.38 and 42.21 kcal/mol at the CCSD(T)//B3LYP level of theory, respectively. The rate constants and branching ratios for the three lower energy H-abstraction channels were calculated using conventional transition state theory with Eckart tunnelling correction at the temperature range 300–2500 K. The predicted rate constants have been compared with the available literature data. Both the forward and reverse rate constants have positive temperature dependence, and the tunnelling effect is only important at low temperatures. The branching ratio calculation shows that channel (2) is predominant and channel (3) is less competitive, while channel (1) is almost neglectable at low temperatures. However, all three channels are important in high-temperature region.