Reactions of the ethyl radical. Part 7.—Addition, dismutation and metathesis with allyl propionate

Abstract

A mechanism is proposed for the photolysis of a gaseous mixture of diethyl ketone and allyl propionate by 3130 Å radiation between 79 and 162°C. This mechanism includes a sequence of addition of the ethyl radical to the double bond of the allyl group, followed by the dismutation of a proportion of the adduct radicals: [graphic omitted] The dismutation is confirmed by the rates of formation of the products: R_C5H10/R_CO2= 1·00 ± 0·02 (79-141 °C), and the activation energies, E₇ and E₈, may be estimated directly from the equations: k₇/k^½₂= 10^{(–7.2±0.3)}exp (–7.7 ± 0.5)10³/RT cm^3/2 molecule^–1/2sec^–1/2, k₈k^½₂/k_7c= 10^(16.2±1.5)exp (–18.5±2.7)10³/RT molecule^1/2 cm^–3/2sec^–1/2, where k₂ refers to 2CH₃CH₂→ C₄H₁₀, and k_7c to CH₃CH₂˙+˙C₅H₁₀ OOCCH₂CH₃→ C₇H₁₅OOCCH₂CH₃, and limits of error are estimated at the 5% probability level. The results are discussed in relation to the behaviour of related allylic systems in the gas phase, and to patterns of chain transfer in the polymerization of allyl monomers in the liquid phase.