Radiation chemistry of acetals. Part 4. Photolysis (λ 185) of liquid 1,3-dioxolan and 2,2-dimethyl-1,3-dioxolan

Abstract

The 185 nm photolysis of the title compounds has been carried out at different temperatures. The quantum yields of the products give satisfactory material balances. The major primary process appears to be ring cleavage at the C(1)–C(5) bond, the biradical ˙CH₂CH₂–O–CR₂–O˙ being an intermediate. Other decomposition pathways may be molecular in nature. Major products from the photolysis at 20 °C of 2,2-dimethyldioxolan are acetone (ϕ= 0.27), propyl acetate (0.24), ethylene (0.18), acetaldehyde (0.13), methyl acetate (0.12), and ethylene oxide (0.11). Dioxolan-2-yl and dioxolan-4-yl radicals are also involved in the photodecomposition. The former radicals are found to rearrange to the β-acyloxyethyl radicals. In the unsubstituted 1,3-dioxolan, the β-formyloxyethyl radical acts as a chain carrier in a reaction leading to ethyl formate as the main product.