Photochemical hydroperoxidation of terpenes I.: Synthesis and characterization of α-pinene, β-pinene and limonene hydroperoxides

The photohydroperoxidation of the stereoisomers of three terpenes ( ( +) and ( -) alpha-pinene, ( +) and ( -) beta-pinene and ( +) and ( -) limonene) has been performed by using photocatalysts, such as zinc oxide, or sensitizers, such as anthracene or rose Bengal, supported on cross-linked polystyrene. Hydroperoxides accumulated alone in the first stages of sensitized oxidation but were always associated with alcoholic and carbonyl products in the case of ZnO. Secondary products obtained for longer exposure times in sensitized oxidations were identified by gas chromatography/mass spectrometry and mechanisms for their formation, deriving from the photolysis of parent hydroperoxides, were suggested. (C) 1997 Elsevier Science S.A.