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

a b s t r a c tThe kinetics and mechanism of (RuCl 3 + OsO 4 ) in combination and, RuCl 3 and OsO 4 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 negativefractional-order on [NaOH]. The order of [PGB] 0 is found to be unity incase of [OsO 4 ], but it is fractional in both RuCl 3 and [RuCl3 + OsO4] catalyzed reactions. The orders with respect to [RuCl 3 ] and [OsO 4 ] are less than one whereas it is unity in case of [RuCl 3 + OsO 4 ]. 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 (RuCl 3 + OsO 4 ) > OsO 4 > RuCl 3 . 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 (RuCl 3 + OsO 4 ) catalyst. It justifies the synergistic effect of (RuCl 3 + OsO 4 ) catalyst on the oxidation of PGB drug. An isokinetic relationship is observed with ˇ = 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.

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The experimental rate laws for the oxidation of N-acetylglucosamine with bromamine-B are: − d[BAB]/dt = k / [BAB] 1 [GlcNAc] 0.69 [HClO 4 ] −0.76 [IrCl 3 ] 0.48 [BSA] −0.33 in acid medium and -d[BAB]/dt = k / [BAB] 1 [GlcNAc] 1 [NaOH] 0.79 in alkaline medium. The IrCl 3 catalyzed reaction is thirteen fold faster than uncatalyzed reaction. Appropriate mechanisms and rate laws were deduced. -CH 3 COOH -NH 3 -CO 2 Keywords IrCl 3 catalysis • N-Acetylglucosamine • Bromamine-B • Acid and alkaline media • Kinetics-mechanism

Naratriptan (NTT), chemically known as N-methyl-2-[3-(1-methyl piperidin-4-yl)-1-H-indol-5-yl] ethane sulfonamide, is an indole derivative widely used in the treatment of migraine headaches. The literature survey indicates that there is no report on the oxidation of NTT from the view point of its kinetic and mechanistic aspects. Also none has examined the task of platinum group metal ions as catalysts in the oxidation of this drug. Therefore, in the present research, oxidation of NTT with chloramine-T (CAT) in alkaline medium has been investigated at 298 K through systematic kinetic study in order to explore the mechanistic picture of this redox system in presence and absence of palladium (II) chloride (Pd(II)) catalyst. The reaction shows a first-order dependence of rate each on