Kinetics and mechanism of the oxidation of some neutral and acidic α-amino acids by tetrabutylammonium tribromide

Abstract

The oxidation of eleven amino acids by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid results in the formation of the corresponding carbonyl compounds and ammonia. The reaction is first order with respect to TBATB. Michaelis-Menten type kinetics is observed with some of the amino acids while others exhibit second-order dependence. It failed to induce polymerization of acrylonitrile. The effect of solvent composition indicate that the rate of reaction increases with increase in the polarity of the medium. Addition of tetrabutylammonium chloride has no effect on the rate of oxidation. Addition of bromide ion causes decrease in the oxidation rate but only to a limiting value. The reaction is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.

Oxidative Degradation ofl-Isoleucine by Au3+Complexes in Weakly Acid Medium: A Kinetic and Mechanistic Investigation

“…This electrostriction phenomenon is another factor responsible for highly negative Δ S # . In several earlier reports involving the oxidation of amino acids such highly negative ΔS # were also noted.…”

Kinetics and mechanism of vanadium(IV) oxidation by tetrabutylammonium tribromide

“…Instead, the interaction would be through the oxygen atom of the vanadyl cation. Such interactions of tribromide ion with oxygen during the formation of a transition state are proposed for oxidation of diols, alcohols and organic acids [1][2][3][4]. Therefore, the probable transition state can be represented as in Figure 2.…”

“…Tetrabutylammonium tribromide(TBATB) has been utilised for oxidation [1][2][3][4] and bromination [5][6][7] of various organic substrates. These tetraalkylammonium polyhalides are enviromentally benign reagents for halogenation as compared with hazardous elemental halogens.…”

Tetrabutylammonium Tribromide

“…22 TBATB has also been used for the oxidation of aliphatic aldehydes to generate the corresponding carboxylic acids, 23 for the oxidation of dimethyl and diphenyl sulfoxide to generate the corresponding sulfones, 24 and for the oxidation of some neutral and acidic α-amino acids to produce the corresponding carbonyl compounds and ammonia. 25 In all cases, the reac-tions were completed in aqueous acetic acid as the solvent, the tribromide ion being the reactive oxidizing species.…”