Kinetics and mechanisms of oxidation of d-fructose and d-lactose by permanganate ion in acidic medium  

作　　者：Rafia Azmat Raheela Naz Noshab Qamar Imran Malik 

机构地区：[1]Department of Chemistry University of Karachi [2]Department of Chemistry, Jinnah University for Women, 5-C Nazimabad Karachi Pakistan [3]International Centre of Chemical and Biological Sciences (ICCBS), University of Karachi

出　　处：《Natural Science》2012年第7期466-478,共13页自然科学期刊（英文）

摘　　要：The oxidations of D-fructose and D-lactose were monitored spectrophotometrically by potassium permanganate in acidic medium at λmax 545 nm. Reaction demonstrated that the two oxidative species of permanganate were involved in an acidic oxidation of the sugars. It was established that respective acids of sugars as well as arabinonic and formic acid were the oxidation products. Respective acids of sugars were the results of reactive oxygen species of permanganate ions in acidic conditions while arabinonic and formic acids due to the cleavage of C__C bond through MnO-4 species. It was first order kinetics with respect to [MnO-4 ], [fructose], [lactose] and [H+]. Hg was used to accelerate the slow oxidation of lactose. Effect of varying salt electrolyte concentration was insignificant showing that the molecular species was involved in the rate determining step. Formic and arabinonic acids and respective acids were analyzed through spot and spectroscopic studies respectively. Reaction was monitored at different temperatures and thermodynamics activation parameters were determined. A mechanism consistent with kinetic studies, spectral evidences, stoichiometry of the reactions and product analysis has been proposed for the oxidation of fructose and lactose in absence and presence of catalyst respectively.The oxidations of D-fructose and D-lactose were monitored spectrophotometrically by potassium permanganate in acidic medium at λmax 545 nm. Reaction demonstrated that the two oxidative species of permanganate were involved in an acidic oxidation of the sugars. It was established that respective acids of sugars as well as arabinonic and formic acid were the oxidation products. Respective acids of sugars were the results of reactive oxygen species of permanganate ions in acidic conditions while arabinonic and formic acids due to the cleavage of C__C bond through MnO-4 species. It was first order kinetics with respect to [MnO-4 ], [fructose], [lactose] and [H+]. Hg was used to accelerate the slow oxidation of lactose. Effect of varying salt electrolyte concentration was insignificant showing that the molecular species was involved in the rate determining step. Formic and arabinonic acids and respective acids were analyzed through spot and spectroscopic studies respectively. Reaction was monitored at different temperatures and thermodynamics activation parameters were determined. A mechanism consistent with kinetic studies, spectral evidences, stoichiometry of the reactions and product analysis has been proposed for the oxidation of fructose and lactose in absence and presence of catalyst respectively.

关 键 词：FRUCTOSE LACTOSE KMNO4 Hg Formic ACID Arabinonic ACID 

分 类 号：O6[理学—化学]