Electrolytically Generated Manganese(III) Sulphate for the Oxidation of 6-Deoxyhexoses in Aqueous Sulphuric Acid Medium: A Kinetic Study

Abstract

Manganese(III) sulphate was prepared by the electrolytic oxidation of

manganese(II) sulphate in aqueous sulphuric acid. The electrolytically

generated Mn(III) species was characterised by spectroscopic and redox

potential studies. Conditions for the study of kinetics of oxidation of

6-deoxy hexoses namely L-rhamnose and L-fucose by Mn(III) in aqueous

sulphuric acid were investigated at λ_max = 500 nm spectrophotometrically.

The rate shows ftrst order dependence on [Mn(III)]₀ and [S]₀ but there is

no dependence of rate on [H⁺]. The effects of added anions like chloride,

sulphate, fluoride, persulphate and reaction product Mn(II) were investigated.

Kinetic and thermodynamic parameters were computed from

Arrhenius and Eyring plots. A mechanism involving the formation of

enediol from 6-deoxyhexose which react with Mn(III) in the rate limiting

step is suggested.