Abstract: The decay of retinol(vitamin A) and retinyl acetate was studied by kinetic measurements in various aqueous micellar solutions. The first-order rate constants were obtained at different temperatures, and from which the corresponding activation parameters were derived. The results show that the decay of retinol and retinyl acetate are much faster in anionic micelles(SDS) than that in cationic micelles(CTAB) and neutral micelles(TX-100), which indicate that the decay is carried out by the protonation of retinol or retinyl acetate first, then one molecular water or acetic acid is lost to produce the carbonium ion, which release the proton followed to generate the anhydroretinol. And the rate constants of the decay of retinol and retinyl acetate show strong dependence on pH, which indicate that, the protonation of retinol or retinyl acetate is the rate-determining step.

Key words: Retinol, Retinyl acetate, Decay, Kinetic measurement, Mechanism, Carbonium ion intermediate