Kinetics of CN(X ²Σ⁺) radical reactions with HCN, BrCN and CH₃CN

Absolute rate constants were obtained for CN (X ²Σ⁺) radical reactions with HCN, BrCN and CH₃CN. The CN radical relative concentration was followed by laser-induced fluorescence (LIF) with a cw ring dye laser on the A ²Π-X ²Σ⁺ (4, 0) band at 621.5 nm. CN radicals were generated by laser photolysis of ICN at 266 nm. The following Arrhenius parameters were obtained over the temperature range 296-578 K: CN+HCN, k=10^-11.41±0.15 exp[-(670±100)/T] cm³ s^-1; CN+BrCN, k=10^-10.7±0.4 × exp[-(1340±330)/T] cm³ s^-1; CN+CH₃CN, k=10^-10.19±0.10 exp[-(1190±70)/T] cm³ s^-1. The rates meas and that of Szekely et al. for CN+HCN could be well fitted by the form, k=10^-16.20T^1.57 exp (-50/T) cm³ s^-1 over the range 300-3000 K, allowing extrapolation to the combustion temperature regime. The measured rates and those of Kayes and Levitt and Clark et al. for the CN+BrCN reaction could be fitted by the form, k=10^-14.18T^1.16 exp(-940/T) cm³ s^-1 the temperature range 300-3000 K. In addition, the non-linearity of these data over a wide range of temperature could be satisfactorily accounted for by transition-state theory calculations for both of these reactions.