Kinetics and mechanism of ruthenium(III) catalyzed oxidation of secondary alcohols by bromamine-​T in hydrochloric acid solutions

The kinetics of oxidn. of 2-​propanol, 2-​butanol, 2-​pentanol, 2-​hexanol, and 2-​heptanol by Na N-​bromo-​p-​toluenesulfonamide (bromamine-​T or BAT) to the corresponding ketones in the presence of HCl and catalyzed by Ru(III) chloride was studied at 30°. The reaction rate shows a first-​order dependence on [BAT] and a fractional-​order each on [alc.]​, [Ru(III)​] and [H+]​. Addn. of the reaction product, p-​toluenesulfonamide, retards the rate. An increase in the dielec. const. of the medium decreases the rate. Variations of ionic strength and halide ion concn. have no effect on the rate. Rate studies in D2O medium show that the solvent isotope effect, k'(H2O)​/k'(D2O)​, is 0.67. Proton inventory studies were carried out using H2O-​D2O mixts. Attempts were made to arrive at a linear free-​energy relation through the Taft treatment and obsd. that the rate consts. do not correlate satisfactorily. An isokinetic relation is obsd. with β = 354K indicating that enthalpy factors control the rate which is also confirmed by the Exner criterion. A mechanism consistent with the obsd. kinetics was proposed and discussed

Prochlorperazine bismethanesulfonate : Sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium

Prochlorperazine bismethanesulfonate (PCPMS) is proposed as a new sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium. PCPMS forms a red-colored species with osmium(VIII) or osmium(VI) instantaneously at room temperature in 5 M phosphoric acid medium. The red species exhibits maximum absorbance at 529 nm. Beer's law is valid over the concentration range 0.05-3.6 ppm for osmium(VIII) and 0.15-6.4 ppm for osmium(VI). Sandell's sensitivity of the reaction is 2.89 nm cm-2 for osmium(VIII) and 4.24 ng cm-2 for osmium(VI). The effects of time, temperature, acidity, order of addition of reagents, reagent concentration, and diverse ions are investigated. The application of the proposed method in the determination of osmium content in synthetic ores has been explored

Oxidation of ethanolamines by sodium N-bromobenzenesulfonamide in alkaline buffer medium: A kinetic and mechanistic study

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 40°C. The three reactions follow identical kinetics with first-order in [oxidant] and fractional-order each in [substrate] and [OH-]. Under comparable experimental conditions, the rate of oxidation increases in the order: DEA > TEA > MEA. The added reaction product, benzenesulfonamide, 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 k′(H2O)/k′(D2O) ≈ 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 β = 430 K indicating that enthalpy factors control the rate. For each substrate, a mechanism consistent with the kinetic data has been proposed. © 2001 John Wiley & Sons, Inc., Int J Chem Kinet

Kinetic and mechanistic studies on the oxidation of norfloxacin by chloramine-B and N-chlorobenzotriazole in acidic medium

The kinetics of oxidation of Norfloxacin 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid by chloramine-B and N-chlorobenzotriazole has been studied in aqueous acetic acid medium (25% v/v) in the presence of perchloric acid at 323 K. For both the oxidants, the reaction follows a first-order dependence on oxidant, a fractional-order on Norfloxacin, and an inverse- fractional order on H+. Dependence of reaction rate on ionic strength, reaction product, dielectric constant, solvent isotope, and temperature is studied. Kinetic parameters are evaluated. The reaction products are identified. The proposed reaction mechanism and the derived rate equation are consistent with the observed kinetic data. Formation and decomposition constants for substrate-oxidant complexes are evaluated. © 1999 John Wiley & Sons, Inc

Oxidation of isoniazid by N-haloarenesulfonamidates in alkaline medium: A kinetic and mechanistic study

The kinetics of oxidation of Isoniazid (INH) by sodium N-haloarenesulfonamidates, chloramine-T (CAT), bromamine-T (BAT), chloramine-B (CAB), and bromamine-B (BAB), has been studied in alkaline medium at 303 K. The oxidation reaction follows identical kinetics with a first-order dependence on each oxidant and INH and an inverse fractional-order on OH-. Addition of the reaction product (p-toluenesulfonamide or benzenesulfonamide) had no significant effect on the reaction rate. Variation of ionic strength and addition of halide ions have no influence on the rate. There is a negative effect of dielectric constant of the solvent. Studies of solvent isotope effects using D2O showed a retardation of rate in the heavier medium. The reaction was studied at different temperatures, and activation parameters have been computed from the Arrhenius and Eyring plots. Isonicotinic acid was identified as the oxidation product by GC-MS. A two-pathway mechanism is proposed in which RNHX and the anion RNX- interact with the substrate in the rate-limiting steps. The mechanism proposed and the derived rate laws are consistent with the observed kinetics. The rate of oxidation of INH increases in the order: BAT>BAB>CAT>CAB. This effect is mainly due to electronic factors

Kinetics and mechanism of oxidation of aspirin by bromamine-T, N-bromosuccinimide, and N-bromophthalimide

The kinetics of the oxidation of aspirin (ASP) by bromamine-T (BAT), N-bromo-succinimide (NBS), and N-bromophthalimide (NBP) has been studied in aqueous perchloric acid at 303 K. The oxidation reaction follows identical kinetics with first-order in [oxidant], fractional-order in [ASP], and inverse fractional-order in [H+]. Under identical experimental conditions the extent of oxidation with different oxidizing agents is in the order: NBS > BAT > NBP, The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction products and halide ions had no significant effect on the reaction rate. The solvent isotope effect was studied using D2O. Kinetic parameters were evaluated by studying the reaction at different temperatures. The reaction products were identified by GC-MS. The proposed reaction mechanism and the derived rate law are consistent with the observed kinetic data. Formation and decomposition constants for ASP-oxidant complexes have been evaluated. Decarboxylation, bromination, and loss of acetic acid gave 2,4,6-tribromophenol. © 1998 John Wiley & Sons, Inc