Reactivity of retinoids and carotenoids in autoxidation

Article abstract of DOI:10.1002/(SICI)1099-1395(199606)9:6<411::AID-POC800>3.0.CO;2-E

The autoxidation of various retinyl polyenes and carotenoids in chlorobenzene at 45 °C and in thin solid films on a support at room temperature was investigated. The compounds used were β-carotene, canthaxanthin, retinyl acetate, methyl (all-E)-retinoate, methyl (13Z)-retinoate, retinal, C₁₈ ketone, β-ionylidene acetaldehyde, ψionone, β-ionone and ethyl sorbate as a model compound. It was shown that the isomerization of polyenyl peroxy radicals occurs during autoxidation of all the compounds studied, excepting β-ionone. A kinetic scheme for the polyene autoxidation process was considered and analysed. The conditions under which the rate constants of elementary reactions may be determined were defined and the rate constants of propagation and termination reactions for different polyenes were evaluated. The disappearance and formation of different functional groups were monitored by the spectroscopic investigation of autoxidation of polyene solid films. Mechanisms of the initial stages of the process are proposed for different polyenes.