Theoretical Study on the Reaction of Nitric Oxide with Propargyl Radical

The reaction of nitric oxide (NO) with propargyl radical (C₃H₃) was investigated at the CCSD(T)/cc-pVTZ//B3LYP/6-311++G(df, pd) level of theory. The rate coefficients of the system were determined by using the RRKM-CVT method with Eckart tunneling correction over a temperature range of 200-800 K and a pressure range of 1.0 × 10^-4 to 10.0 bar. Eight channels proceeding via the barrierless formation of excited intermediate ONCH₂CCH or CH₂CCHNO at the first step were explored. Three favorable channels (i.e., channels producing adduct of ONCH₂CCH and CH₂CCHNO and products of HCN and H₂CCO) were confirmed. The rate coefficients of channels producing adduct of ONCH₂CCH and CH₂CCHNO are comparable and have weak negative temperature dependence and positive pressure dependence. Channel producing products of HCN and H₂CCO is more important at low pressure and high temperature and less important after pressure greater than 1.0 × 10^-2 bar (with a branching ratio less than 6% at 0.1 bar).