Experimental and Theoretical Study of the Product Channels of the C2H + NO Reaction

The product channels of the C2H + NO reaction were studied by transient infrared absorption spectroscopy. HCN, CO, CN, and HNO (produced from HCO secondary chemistry), were,successfully detected. Analysis of the obtained product yields provides an estimation of the branching fractions to be phi(1a)(HCN+C) = 0.77 +/- 0.04 and phi(1b)(HCO+CN) = 0.23 +/- 0.04 at 298 K. The potential energy surface (PES) of the reaction was investigated by ab initio methods at CCSD(T)/6-311++G(d,p)//DFT-B3LYP/6-311++G(d,p) levels as well as higher levels of theory for selected critical points. The singlet potential energy surface shows a low-energy pathway only to the HCN + CO product channel, but a plausible route to HCO + CN products exists on the triplet surface. The computational results are in qualitative agreement with the experimental observations.