Radiolysis of binary mixtures. Part III. Isotope effects in methanolic solutions of deuteriated benzene and deuteriated naphthalene

Abstract

The effect of perdeuteriobenzene and deuteriated naphthalene on the yields of D₂, HD, and CH₃D from methanolic solutions has been examined. The results indicate that hydrogen-atom abstractions contribute significantly to the yield of hydrogen from methanol. This hydrogen yield is unaffected by the addition of scavengers. The isotope effects associated with the formation of the scavenging products anisole, cyclohexadienemethanol, cyclohexa-1,4-diene, phenylcyclohexadiene, and biphenyl formed in methanol–benzene solutions have also been examined. The isotope effect is defined as the ratio of product G-values in CH₃OH + C₆H₆ to those in CH₃OH + C₆D₆. Positive isotope effects have been observed in the formation of biphenyl and anisole, while cyclohexadienemethanol displayed a reverse isotope effect, i.e., smaller than unity. Cyclohexa-1,4-diene and phenylcyclohexadiene show complex isotope effects, which are positive in pure benzene but reverse in benzene–methanol solutions. The decomposition of naphthalene is also associated with a reverse isotope effect. The present isotope effects have been used to elucidate fundamental processes occurring in the radiolysis of binary mixtures containing methanol.