Reactions of iso-propyl radicals with oxygen, hydrogen and deuterium
Abstract
i-C3H7 radicals have been produced by the oxidation of i-C3H7CHO at 440°C. From measurements of the relative yields of C3H6 and C3H8 over a wide range of mixture composition, a value for the ratio k4/k1= 0.003 2 ± 0.000 3 has been obtained. From measurements of the increased yield of C3H8(or C3H7D) in the presence of H2(or D2), the ratios k1/k2s= 3 060 ± 250, k1/k3s= 7 680 ± 300 at 440°C are obtained. i-C3H7·+ O2= C3H6+ HO2(1),i-C3H7·+ H2= C3H8+ H (2s), i-C3H7·+ D2= C3H7D + D (3s), + i-C3H7CHO = C3H8+ i-C3H7ĊO or i-Ċ3H6CHO.(4), The value for k2s/k3s= 2.51 ± 0.20 suggests that E3s–E2s= 800 cal mol–1, which indicates a lowering of the zero-point energy in the transition state of about 1 000 cal mol–1 when H2 is replaced by D2. Absolute rate constants for reactions (1), (2s), (3s) and (4) and Arrhenius parameters for reactions (2s) and (3s), are discussed.