Kinetics of Mn2+ catalysed oxidation of cyclic ketones by lead tetraacetate

Department of Chemistry, Nagarjuna University, Nagarjunanagar-522 510, India E-mail : protbsyamsumlar@yahoo.co.in Manuscript received 14 February· 2005, accepted 6 May 2005 Kinetics of oxidation of a few cyclic ketones — cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone by lead tetraacetate in acetic acid medium with perchloric acid catalysed by Mn2+ has been investigated. Reactions are uniformly zero-order in oxidant. The dependence on substrate is fractional with cyclopentanone, cyclohexanone and cycloheptanone. The dependence on substrate is unity with cyclooctanone. The dependence on Mn2+ is unity with cyclopentanone, zero-order with cyclohexanone and cycloheptanone where as it is fractional with cyclooctanone. Dependence on H+ is fractional in the range studied. With cyclooctanone, rate tends to become zero on H+ at higher concentrations of H+. The results have been analysed on the basis of conformations of these cyclic ketones. Cyclohexanone kinetically reacts faster. The order of reactivity is cyclohexanone > cyclooctanone > cycloheptanone-cyclopentanone