Low-temperature rate coefficients for the reactions of C 2 H + RH → products (RH = C 3 H 8, i -C 4 H 10, n -C 4 H 10, and neo -C 5 H 12 ) have been measured over the temperature range 154−361 K. Measurements were made using laser photolysis of C 2 H 2 to produce C 2 H. Transient infrared laser absorption decays of C 2 H are used to monitor the subsequent reaction in a transverse flow cell. The results show that the rate coefficients for the reactions of C 2 H with propane are independent of temperature while the rate coefficients for the reactions of C 2 H with isobutane, n -butane, and neopentane have a negative temperature dependence. Over the experimental temperature range, the rate constants for C 2 H + RH fit the following Arrhenius expressions: k propane = (7.8 ± 0.4) × 10 -11 exp[(3 ± 12)/ T ], k isobutane = (8.7 ± 0.8) × 10 -11 exp[(28 ± 21)/ T ], k n -butane = (8.3 ± 0.6) × 10 -11 exp[(112 ± 18)/ T ], k neopentane = (7.6 ± 0.9) × 10 -11 exp[(107 ± 30)/ T ] cm 3 molecules -1 s -1 . The corresponding rate constants at 298 K are k propane = 7.9 × 10 -11, k isobutane = 9.6 × 10 -11, k n -butane = 1.2 × 10 -10, k neopentane =1.1 × 10 -10 cm 3 molecules -1 s -1 .
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Hoobler et al. (1997) studied this question.