Rate constants for the elementary reactions between CN radicals and CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂ in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time‐resolved laser‐induced fluorescence experiments have been carried out on the reactions of CN radicals with CH 4 , C 2 H 6 , C 2 H 4 , C 3 H 6 , and C 2 H 2 . They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k (T) = A′(298) (T/298) n exp(−θ/T), yielding: for CH 4 , A′(298) = 7.0 × 10 −13 cm 3 molecule −1 s −1 , n = 2.3, and θ = −16 K; and for C 2 H 6 , A′(298) = 5.6 × 10 −12 cm 3 molecule −1 s −1 , n = 1.8, and θ = −500 K. The rate constants for the reactions with C 2 H 4 , C 3 H 6 , and C 2 H 2 all decrease monotonically with temperature and have been fitted to expressions of the form, k (T) = k (298) (T/298) n with k (298) = 2.5 × 10 −10 cm 3 molecule −1 s −1 , n = −0.24 for CN + C 2 H 4 ; k (298) = 3.4 × 10 −10 cm 3 molecule −1 s −1 , n = −0.19 for CN + C 3 H 6 ; and k (298) = 2.9 × 10 −10 cm 3 molecule −1 s −1 , n = −0.53 for CN + C 2 H 2 . These reactions almost certainly proceed via addition‐elimination yielding an unsaturated cyanide and an H‐atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species.