Oxidation of primary amines by bromamine-B catalyzed by Osmium(VIII) in alkaline medium: A kinetic and mechanistic study

✍ Scribed by S. Ananda; T. Demappa; N. M. Made Gowda

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 166 KB
• Volume: 29
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1997)29:10<737::aid-kin2>3.0.co;2-n

✦ Synopsis

The kinetics of oxidation of the aliphatic primary amines, n-propylamine, n-butylamine, and isoamylamine, by N-sodio-N-bromobenznesulfonamide or bromamine-B (BAB), in the presence of osmium(VIII), has been studied in alkaline medium at 35ЊC. In the presence of the catalyst, the experimental rate law for the oxidation of the amine substrate (S) takes the form, rate ϭ k

which in the absence of the catalyst changes to the form, rate ϭ k[BAB][S][OH Ϫ ] y , where x and y are less than unity. Additions of halide ions and the reduction product of BAB (benzenesulfonamide), and the variation of ionic strength of the solvent medium have no effect on the reaction rate. Activation parameters have been evaluated. The proposed mechanism assumes the formation of a complex intermediate between the active oxidant species, PhSO 2 NBr Ϫ , and the catalyst, OsO 4 , in the rate determining step. This complex then interacts with the substrate amine in fast steps to yield the end products. The average value for the deprotonation constant of monobromamine-B, forming PhSO 2 NBr Ϫ , is evaluated for the Os(VIII) catalyzed reactions of the three amines in alkaline medium as 9.80 ϫ 10 3 at 35ЊC. The average value for the same constant for the uncatalyzed reactions is 1.02 ϫ 10 4 at 35ЊC.