Structure effects in oxidation of aliphatic ketones by thallium(III) sulphate

Abstract

Oxidation kinetics of 11 aliphatic ketones (R1COR2) by thallium(III) sulphate in dilute sulphuric acid have been studied by UV spectrophotometry. The oxidation of methylalkylketones (R2 > CH3) follows the first order kinetics, that of higher dialkyl ketones (R1, R2 > CH3) obeys the second order kinetic equation. Polar and steric effects in the oxidation of aliphatic ketones have been separated by application of LFER to the chosen sets of methyl alkyl ketones (R2 > CH3) and dialkyl ketones (R1, R2 > CH3). Structural factors have a certain effect on the oxidation rate of methyl alkyl ketones, the changes in the reaction rate being ascribable almost exclusively to steric effects of the R2 substituents. The polar effects are very important in the oxidation of dialkyl ketones. Results of the application of LFER suggest that enol formation is the rate-determining step in the oxidations of the two sets of ketones.