Steric effects in the oxidation of oxan-4-ols and thian-4-ols by vanadium(V)

Abstract

The rates of oxidation of 20 heterocyclic alcohols by vanadium(V) have been measured at 60 °C in aqueous acetic acid medium in the presence of sulphuric and perchloric acid. The data indicate an overall second-order reaction at constant acid concentration, first-order each in alcohol and oxidant. The conformational effects on the rates of oxidation of various heterocyclic alcohols are discussed. An interesting observation in the present study is that t-2,t-6-diphenyl-c-3,c-5-dimethyloxan-r-4-ol, an axial alcohol, reacts slower than corresponding equatorial epimer, c-2,c-6-diphenyl-t-3,t-5-dimethyloxan-r-4-ol, which is contrary to general expectations.