Selective Oxidation of Pregabalin Drug Molecule: Exploration of Scope, Reaction Mechanism and Kinetic Modeling

The kinetics and mechanism of (RuCl3 + OsO4) in combination and, RuCl3 and OsO4 alone catalyzed oxidation of pregabalin (PGB) drug with chloramine-T have been investigated at 313 K in aqueous alkaline medium. The kinetic characteristics were found to be varied for each catalyzed reactions. In all the three catalyzed reactions, the reaction rate shows a first-order dependence of rate on [CAT]0 and a negative-fractional-order on [NaOH]. The order of [PGB]0 is found to be unity incase of [OsO4], but it is fractional in both RuCl3 and [RuCl3 + OsO4] catalyzed reactions. The orders with respect to [RuCl3] and [OsO4] are less than one whereas it is unity in case of [RuCl3 + OsO4]. Activation parameters have been evaluated. 2-isobutylsuccinic acid was identified as the oxidation product of PGB. Under identical set of experimental conditions, the reaction rates revealed that all the three catalyzed reactions are about 25 to 71-fold faster than the uncatalyzed reactions. The catalytic efficiency of these catalysts follows the order (RuCl3 + OsO4) > OsO4 > RuCl3. The observed reactivity sequence may be attributed to the different d-electronic configuration of the catalysts. Most noteworthy is the significant catalytic activity of 71-fold in case of (RuCl3 + OsO4) catalyst. It justifies the synergistic effect of (RuCl3 + OsO4) catalyst on the oxidation of PGB drug. An isokinetic relationship is observed with ß = 366 K, indicating that enthalpy factors are controlling the rate. The reaction mechanisms put forward and rigorous kinetic models deduced, give the best fit to the experimental results for each catalyzed reactions

Mechanistic chemistry of oxidation of balsalazide with acidic chloramine-​T and bromamine-​T: A comparative spectrophotometric kinetic study

Balsalazide (BSZ) belongs to a class of non-​steroidal anti-​inflammatory drugs. Kinetics and mechanism of oxidn. of BSZ with sodium N-​halo-​p-​toluenesulfonamides viz., chloramine-​T (CAT) and bromamine-​T (BAT) in HClO4 medium have been spectrophotometrically investigated (λmax = 357 nm) at 303 K. Under comparable exptl. conditions, reactions with both the oxidants follow a first-​order dependence of rate on [BSZ] and fractional-​order dependence on each [oxidant] and [HClO4]​. Activation parameters and reaction consts. have been computed. 2-​hydroxy-​5-​nitrosobenzoic acid and 3-​(4-​nitroso-​benzoylamino)​propionic acid are identified as the oxidn. products of BSZ with both CAT and BAT. The rate of oxidn. of BSZ is about five-​fold faster with BAT than with CAT. Plausible mechanism and related rate law have been deduced for the obsd. kinetics

Synergistic Catalytic Activity of RuCl3 and OsO4 On the Selective Oxidation of Pregabalin Drug Molecule: Exploration of Scope, Reaction Mechanism and Kinetic Modeling

The kinetics and mechanism of (RuCl3 + OsO4) in combination and, RuCl3 and OsO4 alone catalyzed oxidation of pregabalin (PGB) drug with chloramine-T have been investigated at 313 K in aqueous alkaline medium. The kinetic characteristics were found to be varied for each catalyzed reactions. In all the three catalyzed reactions, the reaction rate shows a first-order dependence of rate on [CAT]0 and a negative-fractional-order on [NaOH]. The order of [PGB]0 is found to be unity incase of [OsO4], but it is fractional in both RuCl3 and [RuCl3 + OsO4] catalyzed reactions. The orders with respect to [RuCl3] and [OsO4] are less than one whereas it is unity in case of [RuCl3 + OsO4]. Activation parameters have been evaluated. 2-isobutylsuccinic acid was identified as the oxidation product of PGB. Under identical set of experimental conditions, the reaction rates revealed that all the three catalyzed reactions are about 25 to 71-fold faster than the uncatalyzed reactions. The catalytic efficiency of these catalysts follows the order (RuCl3 + OsO4) > OsO4 > RuCl3. The observed reactivity sequence may be attributed to the different d-electronic configuration of the catalysts. Most noteworthy is the significant catalytic activity of 71-fold in case of (RuCl3 + OsO4) catalyst. It justifies the synergistic effect of (RuCl3 + OsO4) catalyst on the oxidation of PGB drug. An isokinetic relationship is observed with ß = 366 K, indicating that enthalpy factors are controlling the rate. The reaction mechanisms put forward and rigorous kinetic models deduced, give the best fit to the experimental results for each catalyzed reactions

Mechanistic investigation of oxidation of ciprofloxacin by sodium n-chlorobenzenesulphonamide in acid medium. A kinetic study

The kinetics of oxidation of ciprofloxacin (CPF) by sodium N-chlorobenzenesulphonamide or chloramine-B (CAB) in HCI medium at 30 °C shows first order dependence each on oxidant, substrate and H + ion concentrations, but is independent of Cl -. The reaction is subjected to changes in: (a) ionic strength; (b) dielectric constant, and (c) added reaction product, and the subsequent effects on the reaction rate are studied. The reaction was studied at different temperatures, and activation parameters have been computed for the overall reaction from the Arrhenius plot. Oxidation products were identified by TLC and spectral (IR and NMR) analysis. A mechanism involving interaction of conjugate acid (PhSO 2NHCl) and substrate giving an intermediate complex in a slow step has been suggested. The proposed mechanism and the derived rate law are consistent with the observed kinetics

Oxidative conversion of anilines to azobenzenes with alkaline chloramine-T

Anilines are widely used in the manufacture of dyes, medicinals, plastics and perfumes. Anilines are readily oxidized to give products depending on reaction conditions. Conversion of anilines to azobenzene is important in organic synthesis. In the course of this research, optimum conditions for the facile oxidative conversion of anilines to azobenzenes have been established in very good yields. The kinetics of oxidation of aniline, p-methoxyaniline, p-methylaniline, p-carboxylicaniline and p-nitroaniline by chloramine-T (CAT) in NaOH medium shows identical kinetics with a first-order dependence of rate on CATo, fractional-order on Anilineo, and an inverse-fractional order on OH-. Activation parameters and decomposition constants have been determined. Oxidation products were characterized by NMR spectral studies. Isokinetic temperature is 415 K indicating enthalpy as a controlling factor. The rates increased in the order: p-methoxyaniline>p-methylaniline>aniline>p-carboxylicani- line>p-nitroaniline. A Hammett linear free energy relationship is observed for the reaction with Ï=-0.52. Reaction scheme and kinetic rate law were deduced. We have developed a simple and efficient protocol for the synthesis of azobenzenes by anilines in good yields and hence we believe that this methodology will be a valuable addition to the existing methods. © 2015 Korean Institute of Chemical Engineers, Seoul, Kore