Photosensitised reactions of α-pinene

Abstract

The photosensitised decomposition of α-pinene in the liquid phase, using acetophenone or propiophenone as the sensitiser, yields cis- and trans-β-ocimenes as the only products. This is in contrast to pyrolysis, radiolysis, and direct photolysis, where mixtures of products are obtained. Benzophenone does not act as a photosensitiser. It is possible that the reaction involves a vibrationally excited ground-state intermediate. The initial polychromatic quantum yield, (λ= 280–366 mµ), with acetophenone as sensitiser is 0·8.