Oxidation of isoniazid by quinolinium dichromate in an aqueous acid medium and kinetic determination of isoniazid in pure and pharmaceutical formulations.

The kinetics of oxidation of isoniazid in acidic medium was studied spectrophotometrically. The reaction between QDC and isoniazid in acid medium exhibits (4:1) stoichiometry (QDC:isoniazid). The reaction showed first order kinetics in quinolinium dichromate (QDC) concentration and an order of less than unity in isoniazid (INH) and acid concentrations. The oxidation reaction proceeds via a protonated QDC species, which forms a complex with isoniazid. The latter decomposes in a slow step to give a free radical derived from isoniazid and an intermediate chromium(V), which is followed, by subsequent fast steps to give the products. The reaction constants involved in the mechanism are evaluated. Isoniazid was analyzed by kinetic methods in pure and pharmaceutical formulations.     

Deamination and decarboxylation in the chromium(III)-catalysed oxidation of L-valine by alkaline permanganate and analysis of chromium(III) in microscopic amounts by a kinetic method

The kinetics of Cr^III-catalysed oxidation of L-valine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate and L-valine in alkaline medium exhibits 2:1 stoichiometry (KMnO₄:l-valine). The reaction shows first order dependence on [permanganate] and [chromium(III)], and less than unit order dependence each in [L-valine] and alkali concentrations under the experimental conditions. However the order in [L-valine] and [alkali] changes from first order to zero order as the concentrations change from lower to higher respectively. The results suggest the formation of a complex between L-valine and the hydroxylated species of Cr^III. The complex reacts further with 1 mol of alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with 1 mol of alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were obtained and discussed. The title reaction has been utilised to analyse chromium(III) in the 26.0 ng cm^–3–1.0 g cm^–3 range.     

Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of Dimethyl Sulfoxide by N-Chlorosuccinimde in Aqueous Alkaline Medium

The ruthenium(III) catalyzed oxidation of dimethyl sulfoxide by N-chlorosuccinimide (NCS) in aqueous alkaline medium is found to occur via substrate-catalyst complex formation followed by the interaction of active species of NCS viz., HOCl and the complex in a slow step to yield the products with regeneration of the catalyst. One of the products, succinimide, retards the rate of reaction. The reaction is first order in [NCS] and [Ru(III)], lower than first order in [DMSO] and of inverse fractional order in [OH^-]. A suitable mechanism is proposed and the reaction constants of individual steps involved in the mechanism have been evaluated. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of Potential Impurities of Bicalutamide

Bicalutamide is an oral nonsteroidal, anti-androgen drug used for prostate cancer. It binds to the androgen receptor. During the bulk synthesis of bicalutamide, various impurities are formed. The present work details the development of simple processes for the preparation of impurities of bicalutamide, viz bical-sulfoxides (6), bical-deshydroxy (10), bical-desfluoro (10a), bical-2-fluoro (10b), and bical-3-fluoro (10c).     

Effect of Solvent Polarity on the Fluorescence Quenching of Biologically Active 5BAMC by Aniline in Binary Solvent Mixtures

The fluorescence quenching of 5, 6-benzo-4-azidomethyl coumarin (5BAMC) by aniline have been carried in different solvent mixtures of benzene (BN) and acetonitrile (AN) at room temperature by steady state fluorescence measurements. The quenching is found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer plot for the fluorophore in all the solvent mixtures. Various parameters for the quenching process have been determined using the extended S-V equation and have been found to be dependent on the solvent polarity. Further, with the use of finite sink approximation model, it is concluded that the bimolecular reactions quenching reactions are diffusion limited, and the distance parameter R′ and mutual diffusion coefficient D are estimated independently.     

Synthesis of spiro[indolo-1,5-benzodiazepines] from 3-acetyl coumarins for use as possible antianxiety agents

3-Acetyl coumarins (1) when allowed react with isatin (2) gave corresponding 3-(3′-hydroxy-2′-oxo indolo) acetyl coumarins (3), which on dehydration afforded the correspondingα,β-unsaturated ketones (4). Cyclocondensation of (4) with substitutedo-phenylene diamines resulted in novel 3-coumarinyl spiro[indolo-1,5-benzodiazepines] (5). Structures of all the compounds have been established on the basis of their IR, NMR and mass spectral data and have been screened for their antimicrobial activity and antianxiety activity in mice