Oxidation of aspirin by N-sodio-N-bromobenzene sulphonamide (bromamine-B) in acid medium; a kinetic and mechanistic study

The kinetics of the oxidation of aspirin (ASP) by bromamine-B (BAB) has been studied in aqueous perchloric acid at 303 K. Decarboxylation, bromination and loss of acetic acid gave the reaction product 2,4,6-tribromophenol and was identified by GC-MS. The rate shows first order dependence on BAB, fractional order in ASP and inverse fractional order in H +. The rate decreased with decreasing dielectric constant of the medium. The variation of ionic strength and the addition of the reaction product (benzene sulphonamide) and halide ions had no significant effect on the reaction rate. Thermodynamic parameters were evaluated. The solvent isotope effect was studied using D 2O

Kinetics of oxidation of cysteine by bromamine-T in H2SO4 medium

The kinetics of oxidation of cysteine by sodium N-bromotoluene sulfonamide (bromamaine-T or BAT) in H2SO4 medium has been carried out at 30 degrees C. The effect of H+] and SO42-], variation of ionic strength and dielectric constant to the medium on the rate of reaction has been studied. Addition of the reaction product, toluene sulfonamide had no effect on the rate of reaction. Thermodynamic parameters have been evaluated by studying the kinetics at various temperatures. Suitable mechanism has been proposed in consistency with the kinetic results

Kinetics of the ruthenium(III) catalyzed oxidation of amides by sodium N-bromotoluenesulfonamide in hydrochloric acid solution

The kinetics of Ru(III) catalyzed oxidations of urea, methylurea and ethylurea by sodium N-bromo-p-toluenesulfonamide, also known as bromamine-T (BAT), in HCl solution has been studied at 30 degrees C. The reaction rate shows a first-order dependence each on BAT], amide] and Ru(III)I and fractional-order on H+]. Additions of halide ions and the reaction product of BAT (p-toluenesulfonamide) and the variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Activation parameters have been evaluated. A Taft linear free energy relationship is observed for the reaction, with rho*= -0.64 and -2.95 and delta = -0.25, indicating that electron donating groups enhance the rate. An isokinetic relationship is observed with beta = 391 K indicating that enthalpy factors control the rate. The existence of the relationship has been supported by the Exner criterion. The protonation constant of monobromamine-T calculated from a plot of 1/k' versus 1/H+] is 29.15. Mechanisms consistent with the observed kinetic data have been proposed

Ruthenium(III) catalyzed oxidation of aliphatic primary amines by bromamine-T in hydrochloric acid medium: A kinetic study

The kinetics of the ruthenium(III) catalyzed oxidation of the aliphatic primary amines n-propylamine, n-butylamine and isoamylamine, by sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) in HCI medium has been studied in the temperature range 298-313 K. The reaction rate shows a first-order dependence each on BAT, amine, and ruthenium(III). The reaction also shows an inverse fractional-and inverse first-order dependence on acid at low and high HCl] ranges, respectively. Added halide ions and p-toluenesulfonamide (reduction product of BAT), and variation of ionic strength of the solvent medium have no effect on the rate. The activation parameters have been evaluated. Mechanisms consistent with the kinetic data have been proposed. The protonation constant of monobromamine-T has been evaluated to be 29 +/- 2. A Taft LFE relationship is observed for the ruthenium(lll) catalyzed reaction with p* = -4.6 indicating that the electron donating groups enhance the reaction rate. An isokinetic relationship is observed with B = 355 K indicating that enthalpy factors control the rate

Mechanistic investigations of the oxidation of indoles with bromamine-T in alkaline medium catalyzed by Os(VIII)

The kinetics of oxidation of 5 substituted indoles (Y-In, where Y = H, Cl, Br, NO2, CH3 and OCH3) by sodium-N-bromo-p-toluenesulphonamide or bromamine-T (BAT) in the presence of NaOH and catalyzed by Os(VIII) in 10 % vol. methanol medium has been studied at 303 K. The corresponding oxindoles and p-toluenesulphonamide (PTS) have been characterized as reaction products. The reaction rate shows a first order dependence each on indole](0) and BAT](0), a fraction order on Os(VIII)] and an inverse first order on OH-]. Addition of p-toluenesulphanamide, chloride, bromide and variation of ionic strength of the medium have no effect on the reaction rate. There is a negative effect of dielectric constant of the solvent. Activation parameters have been calculated from the Arrhenius plots. The Hammett correlation of substituent effects indicates a linear free energy relationship with rho+ = - 1.0 showing the formation of an electron deficient transition state. From enthalpy-entropy relationships and the Exner correlations, the isokinetic temperature beta was found to be 330 K, indicating enthalpy as a controlling factor. Proton inventory studies in H2O-D2O mixtures have shown the involvement of a single exchangeable proton of OH- ion in the transition state. A mechanism consistent with the observed kinetics has been proposed

Fluorine substituted thiomethyl pyrimidine derivatives as efficient inhibitors for mild steel corrosion in hydrochloric acid solution: Thermodynamic, electrochemical and DFT studies

Three new 5-fluoro-2- methylthio substituted pyrimidine derivatives have been synthesized and characterized by H-1 NMR spectroscopy and Mass spectrometry. Corrosion inhibition characteristics of the synthesized pyrimidine derivatives have been studied on mild steel (MS) in 0.5 M hydrochloric acid solution at various temperatures (303-333 K) using mass loss and electrochemical techniques. The obtained weight loss, electrochemical impedance and potentiodynamic polarization data indicate that the corrosion inhibition efficiency is directly proportional to concentration of the inhibitors. The Adsorption process on MS surface obeyed Langmuir isotherm model. Scanning electron microscopy (SEM) was used to characterize surface morphology of the MS specimen in absence and presence of pyrimidine derivatives. Density functional theory (DFT) calculations using B3LYP functional with 6-311+G (d,p) level was used to establish the relationship between molecular structure and corrosion inhibition efficiency. Electrochemical analysis indicated that pyrimidine derivatives inhibit the corrosion by adsorbing on the metal surface. Mixed-type of corrosion inhibition activity with anodic predominance was proposed by polarization studies. (C) 2020 Elsevier B.V. All rights reserved