CONFORMATIONAL AND STERIC EFFECTS ON THE OXIDATION OF SOME SUBSTITUTED TETRAHYDROTHIOPYRAN-4-ONES AND THEIR 1,1-DIOXIDES BY PYRIDINIUM FLUOROCHROMATE

Kinetics of oxidation of the title compounds by pyridinium fluorochrom ate (PFC) in the presence of perchloric acid in aqueous acetic acid me dium has been studied. The reactions show first order dependence each on [oxidant] and [substrate] and are observed to be acid-catalysed. An increase in polarity of the medium is found to decrease the rate and the variation in ionic strength of the medium has no significant influ ence on the rate of oxidation. All the reactions have been carried out at four different temperatures and various activation parameters are evaluated. The oxidation products have been isolated and characterised . Plausible mechanisms consistent with the observed kinetic results ha ve been formulated. The relative reactivities of these compounds have also been rationalised based on their conformational differences and s teric factors.