chloramine-T In Hydrochloric Acid Medium Research Articles

Kinetics and Mechanism of Oxidation of Alizarin Yellow R Dye by Chloramine-T in Hydrochloric Acid Medium. A Spectrophotmetric Study

Kinetics of oxidative decolorization of alizarin yellow R (AYR) by chloramine-T (CAT) in hydrochloric acid (HCl) medium at 304 K has been investigated spectrophotometrically at λmax520 nm. The reaction showed first-order rate dependence on [CAT] and [AYR]o and fractional order dependence on [HCl]. Stoichiometry of the reaction was found to be 1:1 with respect to the substrate and oxidant respectively. The oxidation products were identified by spectral analysis. Variation of ionic strength had no effect on the rate. Addition of p-toluene sulphonamide (PTS) did not retard the rate of the reaction. Activation parameters have been computed. Probable mechanism and the relevant rate law have been deduced for the observed kinetic results.

Use of chloramine-T and two dyes in the sensitive determination of stavudine in pharmaceuticals

Three new methods are described for the assay of stavudine (STV) in bulk drug and in dosage forms using chloramine-T (CAT) and two dyes, methyl orange and indigocarmine, as reagents. Titrimetry involves treating STV with a measured excess of CAT in hydrochloric acid medium, and after the oxidation of STV is judged to be complete, the unreacted oxidant is determined iodometrically. Spectrophotometric methods entail the addition of a known excess of CAT to STV in hydrochloric acid medium followed by determination of residual oxidant by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (Method A) or indigo carmine and measuring the absorbance at 610 nm (Method B). In all the methods, the amount of CAT reacted corresponds to the amount of STV. In titrimetric method, the reaction follows 1:1 stoichiometry (STV: CAT), and is applicable over the range 1.5-10 mg of STV. In spectrophotometric methods, the absorbance is found to increase linearly with concentration of STV. The systems obey Beer's law for 0.2-2.0 and 1.0-10.0 mg/mL for method A and method B, respectively. The apparent molar absorptivities are calculated to be 5.7x10(4) and 1.5x10(4) L/mol/cm for method A and method B, respectively, and the corresponding Sandell sensitivity values are 0.004 and 0.015 µg/cm². The limits of detection and quantification are reported for both methods. Intra-day and inter-day precision and accuracy of the developed methods were evaluated as per the current ICH guidelines. The methods were successfully applied to the assay of STV in tablet and capsule formulations and the results were compared with those of a reference method by applying Student's t-test and F-test. No interference was observed from common tablet adjuvants. The accuracy and reliability of the methods were further ascertained by performing recovery experiments via standard-addition method.

Mechanistic studies on the Ru(III)-catalyzed oxidation of some aromatic primary diamines by chloramine-T in hydrochloric acid medium: A kinetic approach

Abstract The kinetics of ruthenium(III) chloride (Ru(III))-catalyzed oxidation of aromatic primary diamines viz., 4,4′-diaminodiphenyl methane (DDM), 4,4′-diaminodiphenyl sulfone (DDS) and 4,4′-diaminodiphenyl ether (DDE), by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in HCl medium have been investigated at 298 K. Under comparable experimental conditions, the three oxidation reactions follow identical kinetics with first-order dependence both on [oxidant]0 and [Ru(III)], and less than unity order dependence on [Amine]0 and on [H+]. The stoichiometry for each reaction was found and the oxidation products were identified through GC–MS analysis. The reactions were subjected to changes in (a) ionic strength, (b) p- toluenesulfonamide, (c) dielectric permittivity, (d) halide ions, (e) solvent isotope and (f) temperature effect. The reaction mixture fails to initiate the polymerization of acrylonitrile. The activation parameters for the overall reaction were deduced from Arrhenius plots. Under comparable experimental conditions, the relative reactivity of these amines towards CAT is in the order: DDS > DDE > DDM. This reactivity trend may be attributed to electronic factors. The isokinetic temperature (β) of 350 K calculated from enthalpy–entropy relationships and the Exner criterion was much higher than the experimental temperature of 298 K employed in the present study, indicating that the reaction is under enthalpy control. Under the identical set of experimental conditions, the kinetics of Ru(III)- catalyzed oxidation of amines by CAT has been compared with those of uncatalyzed reactions; the catalyzed reactions are found to be about 5-fold faster. The catalytic constant (KC) has been calculated for each amine at different temperatures. The values of activation parameters with respect to Ru(III)-catalyst have been evaluated from the plots of log KC versus 1/T. The protonated species CH3C6H4SO2N+H2Cl has been postulated as the reactive oxidizing species of CAT. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.

Ru(III)-catalysed oxidation of some N-heterocycles by chloramine-T in hydrochloric acid medium: a kinetic and mechanistic study

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- N-chloro- 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 = k [CAT] 0 [ S ] 0 x [H +] y [Ru(III)] z , 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 2O 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 2O +Cl has been postulated as the reactive oxidizing species. The reaction mechanism and the derived rate law are consistent with the observed experimental results.

Spectrophotometric determination of verapamil hydrochloride in drug formulations with chloramine-T as oxidant.

A new spectrophotometric method is described for the determination of verapamil hydrochloride, based on its oxidation with chloramine-T in hydrochloric acid medium. It produces a yellow colored compound with maximum absorbance at 425 nm. Beer's law was obeyed in the concentration range 0-340 micro g mL(-1) with molar absorptivity 2 x 10(3) L mol(-1) cm(-1) and RSD 0.3-0.82%. All variables were studied to optimize the reaction conditions. No interferences were observed from the common excipients present in the formulations. The method has been applied successfully to the determination of the drug in pharmaceutical preparations. Statistical comparison of the results with those from the reference method reveals excellent agreement and confirms that accuracy and precision are not significantly different.

A highly sensitive spectrophotometric method for the determination of some phenothiazine antipsychotics using chloramine-T and indigocarmine.

A new simple, accurate and precise spectrophotometric method for the determination of six phenothiazine drugs in pure form and in dosage forms is described. The method is based on the oxidation of the studied drugs by a known excess of Chloramine-T in hydrochloric acid medium and subsequent determination of the unreacted oxidant by reacting it with indigocarmine in the same acid medium. The reacted oxidant corresponds to the drug content. The colored species exhibits maximum absorption at 610 nm. The apparent molar absorptivity values and Sandell sensitivity values are in the range 1.53 x 10(4)-2.96 x 10(4) l mol-1 cm-1 and 13.75-37.15 ng cm-2, respectively. The method is highly sensitive and suitable for 1-15 micrograms ml-1 concentrations with the detection limits being in the range, 0.0651-0.1724 microgram ml-1. The method was successfully applied to the studied drugs in their dosage forms. The results are reproducible within +/- 1% and compare favorably with those obtained by the procedures of the British Pharmacopeia.

A reinvestigation of the reaction between Prop-2-en-1-ol and chloramine-T in hydrochloric acid medium

Contrary to a previous report the reaction of prop-2-en-1-ol with chloramine-T in 1 M HCl gives 2,3-dichloropropan-1-ol not prop-2-en-1-al. For HCl concentrations of 0.075 M and higher the reaction is of first order each with respect to the concentration of chloramine-T, H+ and Cl- ions, but independent of the alcohol. As chloroamines in these conditions are known to give chlorine, it is proposed that the reaction involves the addition to the unsaturated alcohol of molecular chlorine which is produced by a prior, rate-determining reaction between H+ and Cl- ions with chloramine-T.

Kinetic and mechanistic studies on the oxidation of arginine and histidine by chloramine-T in hydrochloric acid medium

The oxidation of amino acids by chloramine-T (CAT) in HCl medium at 30°C indicates simultaneous catalysis by H+ and Cl− ions in the HCl concentration range of 0.04–0.12 M. The reaction is first order with respect to concentrations [CAT], [H+] and [arginine], but zero order with respect to [histidine]. The rate depends also on Cl− concentration following 0.7th order. At HCl concentrations >0.12 M, the rate equation is:w=k[CAT] [amino acid]0.6 and is independent of the [Cl−]. A suitable mechanism has been suggested.

Kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium

Kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium

Kinetics and mechanism of oxidation of acetone, ethyl methyl ketone and diethyl ketone with chloramine-T in hydrochloric acid medium

The kinetics of oxidation of aliphatic ketones (acetone, ethyl methyl ketone and diethyl ketone) by chloramine-T in presence of hydrochloric acid (0.1 to 0.3M) have been investigated at 30 °C. The rate of disappearance of chloramine-T has been found to be first order each with respect to oxidant, ketone and [H+], in the range of the acid concentrations studied. The thermodynamic and kinetic parameters have been evaluated by determining the rate constants at different temperatures. The products of the reaction have been identified as chloroketones by their NMR spectra. The solvent isotope effect has been studied in the case of the oxidation of acetone and ethyl methyl ketone. A mechanism has been proposed.

Kinetics of oxidation of allyl alcohol by chloramine-T in hydrochloric acid medium: effect of high acid concentrations

The kinetics of oxidation of allyl alcohol by chloramine-T in presence of hydrochloric acid(0.15-0.29M) has been studied. At 0�C the rate is first order with respect to chloramine-T, second order in [H+] and independent of the alcohol concentration. The energy of activation and entropy of activation of the reaction have been found to be 55.6 kJ mol -1 and -153 J K-1 respectively. A mechanism is proposed.

Kinetics and mechanism of oxidation of allyl alchohol by chloramine-T in hydrochloric acid medium

The kinetics of oxidation of allyl alcohol by chloramine-T in presence of hydrochloric acid (0.04-0.13M ) has been studied at O�C. The reaction shows first-order dependence on chloramine-T and hydrogen ion concentration and is independent of the concentration of alcohol. The energy and entropy of activation of the reaction have been found to be 12.3 kcal mol-1 and -33.2 e.u. respectively.Ionic strength has very little influence on the rate of reaction. A mechanism in terms of a fast interaction between allyl alcohol and hypochlorous acid formed by the hydrolysis of N-chloro-p-toluenesulphonamide in a slow step is proposed.