Reaction of n-propyl radicals with oxygen, hydrogen and deuterium

Abstract

n-C3H7 radicals have been produced by the oxidation of n-C3H7CHO at 450°C. By measuring the relative yield of C3H6 and C3H8, a value for the ratio k4/k1= 0.040 ± 0.005 has been obtained. A value of k4 can be obtained, based on the value of 2.9 × 1010 l. mol–1 s–1 assumed for the combination of two C3H7 radicals, which gives k1= 3.1 × 107 at 450°C. By measuring the increased yield of C3H8(or C3H7D) in the presence of H2(or D2), the ratios k1/k2= 347 ± 10, k2/k3= 2.3 ± 0.2 at 450°C are obtained. n-C3H7+ O2→ C3H6+ HO2(1), n-C3H7+ H2→ C3H8+ H (2), n-C3H7+ D2→ C3H7D + D (3), n-C3H7+ C3H7CHO → C3H8+ C3H7CO. (4)

The value for k2/k3 suggests that E3–E2= 0.7 kcal mol–1 which indicates a lowering of the zero-point energy in the transition state by about 1.1 kcal mol–1 when H2 is replaced by D2. Using entropy data, and the Arrhenius parameters for reaction (– 2), A2= 2.6 × 109 and E2= 14.8 kcal mol–1.