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/k_2s= 3 060 ± 250, k₁/k_3s= 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 k_2s/k_3s= 2.51 ± 0.20 suggests that E_3s–E_2s= 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.