Photochemical Reactions of Aromatic Compounds. IX. Photochemical Reactions of Dimethylaniline with Halobenzenes

Abstract

Abstract Irradiation of methanolic solutions of DMA containing halobenzenes (chlorobenzene, bromobenzene and iodobenzene) and triethylamine (TEA) gave TEA hydrohalides in quantitative yields along with benzene (II), di-phenyl, N-methylaniline, o- and p-dimethylaminodiphenyls (IV and V). From the properties of the products and spectroscopic and kinetic data, it was suggested that the reactions took place by way of electron transfer from DMA to halobenzenes. The electron transfer reactions were classified into a short range type (chlorobenzene and bromobenzene) and a long range type (iodobenzene) on the basis of the product ratio (IV+V)/II and the proportion of benzene-d1 in the benzene fraction obtained from the photoreactions of DMA-d6 with halobenzenes. From the kinetic and fluorescence data, an exciplex mechanism was suggested for the photoreactions with chlorobenzene and bromobenzene, and a direct electron transfer mechanism in the case of iodobenzene.