Photooxidation of Tetrabromofuran in Benzene

Abstract

Photooxidation in the solid state of tetrabromofuran (1) gave the tetrabromo -γ-lactone (2) (30%), but in benzene solution gave dibromomaleic anhydride (3) (85%). Possible radical chain mechanisms for the transformations (1) → (2) and (1) → (3) are suggested. A molecular orbital discussion attempts to explain how an initial π-π* transition of a C=C bond in (1) leads to a σ C-Br bond fission. Use of e.p.r . to detect radicals in the transformations (1) → (2) and (1) → (3) failed.