Kinetics of oxidation of acidic amino acids (glutamic acid (Glu) and aspartic acid (Asp)) by sodium N-bromobenzenesulphonamide (bromamine-B or BAB) has been carried out in aqueous HClO 4 medium at 30°C. The rate shows firstorder dependence each on [BAB] o and [amino acid] o and inverse first-order on [H + ]. At [H + ] > 0⋅60 mol dm-3 , the rate levelled off indicating zero-order dependence on [H + ] and, under these conditions, the rate has fractional order dependence on [amino acid]. Succinic and malonic acids have been identified as the products. Variation of ionic strength and addition of the reaction product benzenesulphonamide or halide ions had no significant effect on the reaction rate. There is positive effect of dielectric constant of the solvent. Proton inventory studies in H 2 O-D 2 O mixtures showed the involvement of a single exchangeable proton of the OHion in the transition state. Kinetic investigations have revealed that the order of reactivity is Asp > Glu. The rate laws proposed and derived in agreement with experimental results are discussed.

The kinetics of the ruthenium(III) chloride (Ru(III))-catalysed oxidation of five N-heterocycles (S) viz. imidazole (IzlH), benzimidazole (BzlH), 2-hydroxybenzimidazole (2-HyBzlH), 2-aminobenzimidazole (2-AmBzlH) and 2-phenylbenzimidazole (2-PhBzlH) by sodium-Nchloro-p-toluenesulfonamide (chloramine-T; CAT) in the presence of HCl has been studied at 313 K. The oxidation reaction follows the identical kinetics for all the five N-heterocycles and obeys the rate law, rate, where x, y and z are less than unity. Addition of p-toluenesulfonamide (PTS) retards the reaction rate. Variation of ionic strength of the medium and the addition of halide ions show negligible effect on the rate of the reaction. The rate was found to increase in D 2 O medium and showed positive dielectric effect. The reaction products are identified. The rates are measured at different temperatures for all substrates and the composite activation parameters have been computed from the Arrhenius plots. From enthalpy-entropy relationships and Exner correlations, the calculated isokinetic temperature (β) of 392 K is much higher than the experimental temperature (313 K), indicating that, the rate has been under enthalpy control. Relative reactivity of these substrates are in the order: 2-HyBzlH > 2-AmBzlH > BzlH > IzlH > 2-PhBzlH. This trend may be attributed to resonance and inductive effects. Further, the kinetics of Ru(III)-catalysed oxidation of these N-heterocycles have been compared with uncatalysed reactions (in the absence of Ru(III) catalyst) and found that the catalysed reactions are 16-20 times faster. The catalytic constant (K C ) was also calculated for each substrate at different temperatures. From the plots of log K C versus 1/T, values of activation parameters with respect to the catalyst have been evaluated. H 2 O + Cl has been postulated as the reactive oxidizing species. The reaction mechanism and the derived rate law are consistent with the observed experimental results.

The kinetics of oxidation of five dipeptides (DPP) viz., glycylglycine (Gly-Gly), L-alanyl-L-alanine (Ala-Ala), L-valyl-L-valine (Val-Val), L-leucyl-L-leucine (Leu-Leu) and phenylglycyl-phenylglycine (Phg-Phg) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in NaOH medium was studied at 308 K. The reactions follow identical kinetics for all the dipeptides, being first-order dependence each on [CAT] has no significant effect on the rate of reaction. The reaction rate was found to increase with increase in ionic strength of the medium. The solvent isotope effect was studied using D 2 O. The activation parameters for the reaction were computed from Arrhenius plots. Equilibrium and decomposition constants were evaluated. The oxidation products of the dipeptides were identified as their corresponding aldehydes. An isokinetic relationship was observed with β＝352 K, indicating that enthalpy factors control the reaction rate. CH 3 C 6 H 4 SO 2 NCl -of the oxidant has been postulated as the reactive oxidizing species. Under comparable experimental conditions, the rate of oxidation of the dipeptides increases in the order: Phg-Phg＞Ala-Ala＞Val-Val＞Leu-Leu＞Gly-Gly. The kinetics of oxidation of the dipeptides have also been compared with those of their corresponding monomer amino acids. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.

in Wiley InterScience (www.interscience.wiley.com).Oxidation of isatins (isatin, 5-methylisatin, 5-bromoisatin, and 5-nitroisatin) to their corresponding anthranilic acids was performed with sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) as an oxidant and ruthenium trichloride (Ru(III)) as a catalyst in HCl medium at 30 6 0.18C. The four reactions follow identical kinetics with a first-order dependence each on [BAT] . Activation parameters have been deduced for the composite reaction. The rates satisfactorily correlate with the Hammett r relationship and the reaction constant q is 20.36 signifies that the electron donating groups accelerate the reaction while the electron withdrawing groups retard the rate. An isokinetic relationship is observed with b 5 360 K, indicating that enthalpy factors control the reaction rate. Oxidation products of isatins were identified as their corresponding anthranilic acids by GC-MS analysis and the yields were found to be [90%. Under similar experimental conditions, the kinetics of Ru(III)-catalyzed oxidation of isatins with BAT has been compared with that of uncatalyzed reactions, revealing that the catalyzed reactions are three to fourfold faster. The observed results have been explained by a plausible mechanism and the related rate law has been deduced. The method adopted for the oxidation of isatins to anthranilic acids in the present work offers several advantages and can be scaled up to industrial operation. 2008 American Institute of Chemical Engineers AIChE J, 54: 756-765, 2008

The kinetics of oxidation of ethanolamines, monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA), by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline buffer medium (pH 8.7-12.2) has been studied at 40ЊC. The three reactions follow identical kinetics with first-order in [oxidant] and fractional-order each inUnder comparable experimental conditions, the rate of oxidation increases in the order:The added reaction product, benzenesulfonamide, DEA Ͼ TEA Ͼ MEA. retards the reaction rate. The addition of halide ions and the variation of ionic strength of the medium have no significant effect on the rate. The dielectric effect is negative. The solvent isotope effect kЈ(H 2 O)/kЈ(D 2 O) Ϸ 0.92. Activation parameters for the composite reaction and for the rate-limiting step were computed from the Eyring plots. Michaelis-Menten type of kinetics is observed. The formation and decomposition constants of ethanolamine-BAB complexes are evaluated. An isokinetic relationship is observed with indicating that ␤ ϭ 430 K enthalpy factors control the rate. For each substrate, a mechanism consistent with the kinetic data has been proposed.