Micelle Catalyzed Oxidation of D-Mannose by Cerium (IV) in Sulfuric Acid  

作　　者：KABIR-UD-DIN ALI Mohd. Sajid KHAN Zaheer 

机构地区：[1]Chemistry Department, Aligarh Muslim University, Aligarh 202002, UP, India [2]Chemistry Department, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India

出　　处：《物理化学学报》2008年第5期810-816,共7页Acta Physico-Chimica Sinica

摘　　要：Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40 ℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium (IV), which decreased with increasing [H2SO4]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (IV) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium (IV). From the kinetic data, micelle-cerium (IV) binding and rate constants in micellar medium were evaluated. The anionic micelle of sodium dodecyl sulfate plays no catalytic role. The oxidation has the rate expression: -d[Ce(IV)]= k1Kc1[D-mannose][Ce(IV)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.Kinetics of D-mannose oxidation by cerium （IV） was studied in a sulfuric acid medium at 40 ℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium （IV）, which decreased with increasing [H2SO,]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium （IV） to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide （CTAB） micelles was best explained by the Menger- Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium （IV）. From the kinetic data, micelle-cerium （IV） binding and rate constants in micellar medium were evaluated. The anionic micelle of sodium dodecyl sulfate plays no catalytic role. The oxidation has the rate expression： -d[Ce（IV）]= k1Kc1[D-mannose][Ce（IV）]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.

关 键 词：甘露糖 胶束 催化剂 硫磺酸 化学分析 

分 类 号：O643.3[理学—物理化学]