Direct Ab Initio Dynamics Study of Radical C4H (X̃2Σ+) + CH4 Reaction

The methane (CH4) hydrogen abstraction reaction by linear butadiynyl radical C4H (CCCCH) has been investigated by direct ab initio dynamics over a wide temperature range of 100−3000 K, theoretically. The potential energy surfaces (PESs) have been constructed at the CCSD(T)/aug-cc-pVTZ//BB1K/6-311G(d,p) levels of theory. Two different hydrogen abstraction channels by C1 and C4 of C4H (C1C2C3C4H) have been considered. The results indicate that the C1 position of C4H is a more reactive site. The electron transfer behaviors of two possible channels are also analyzed by quasi-restricted orbital (QRO) in detail. The rate constants calculated by canonical variational transition-state theory (CVT) with the small-curvature tunneling correction (SCT) are in excellent agreement with available experimental values. The normal and three-parameter expressions of Arrhenius rate constants are also provided within 100−3000 K. It is expected to be helpful for further studies on the reaction dynamics behaviors over a wide temperature range where no experimental data is available so far.