A kinetic study of RuIII catalyzed oxidation of galactose and cyclopentanol by potassium bromate in alkaline medium

Abstract

in alkaline medium using mercuric acetate as a scavenger for Br - ion (galac) as well as co-catalyst (cyclopen), have been studied in the temperature range 30-45 °C. The reactions exhibit first-order kinetics with respect to oxidant and catalyst while zero-order kinetics with respect to substrate was observed in case of both galactose and cyclopentanol. For cyclopentanol, a positive effect on the rate of reaction were observed on successive addition of [Hg(OAc) 2 ] and [Cl - ] whereas [OH - ] exhibited an inverse fractional order. In case of galactose, [OH - ] and [Hg(OAc) 2 ] have no effect on the reaction velocity. A positive fractional order in acetic acid concentration (AcOH) and negligible effect of ionic strength of the medium were observed. The reactive species of RU III in alkaline medium is [RuCl 2 (H 2 O) 3 (OH)] (galac) and [RuCl 3 (H 2 O) 2 OH] -1 (cyclopen) under the experimental pH range. A suitable mechanism in conformity with the kinetic observation has been proposed. The various activation parameters such as energy of activation (ΔE*), Arrhenius factor (A), entropy of activation (ΔS*) were calculated from the rate measurements at 30, 35, 40 and 45 °C. A rate law has been derived on the basis of data obtained.