Search

Ruthenium(III) catalyzed oxidation of propane-1,3-diol by potassium periodate was studied in aqueous perchloric acid medium. Orders of reaction with respect to concentrations of oxidant, substrate, acid and catalyst were determined. First order in oxidant and catalyst concentrations, and inverse fractional order in acid medium were observed. In addition, substrate inhibition (i.e. a decrease in reaction rate with an increase in substrate concentration) was observed. Effect of addition of salt and solvent was studied. Based on the studies of temperature variation, Arrhenius parameters were calculated. Plausible mechanism was also proposed based on observed kinetics.

Objective: To study the kinetics of periodate oxidation of polyethylene glycol-600 (PEG-600), a familiar non-toxic polymer used in pharmaceutical and other fields of industry. Methods: Reactions were carried out in alkaline medium and measured the kinetics by iodometry. One oxygen atom loss or two electrons transfer was observed per each molecule of periodate i.e., the rate of reaction was measured periodate converts to iodate because the formed iodate species is unable to oxidize the substrate molecules. Results: Based on log (a-x) versus t plots, order w. r. t. oxidant (periodate) is unity. Reactions were found to be independent of substrate (PEG-600) concentration. A decrease in rate with an increase in alkali concentration [OH–] was found and order was inverse fractional. Temperature dependence of reaction rate was studied and then calculated the corresponding Arrhenius parameters. Conclusion: An appropriate rate law was proposed by considering the above experimental results.

A simple, selective, accurate and low-cost spectrophotometric method has been described for determination of satranidazole in bulk and pharmaceutical formulations. The developed method involves the formation of chloroform extractable colored ion-association complex of satranidazole with Tropaeolin OOO (TPooo). The extracted colored complex showed absorbance maximum at wavelength 484 nm and obeying Beer′s law in the concentration 4-20 μg mL-1 with the correlation coeffiecent of 0.9998. The results of statistical analysis of the proposed method reveals high accuracy and good precession. Thus, the proposed method can be used commercially for the determination of satranidazole in bulk and pharmaceutical formulations.

Kinetics of PEG-200 oxidation by potassium periodatewas studied in alkaline medium. First-order dependence of reaction on periodate was observed. Rate of the reaction was found to be independent of substrate concentration. An inverse fractional order with respect to alkaliwas shown. Arrhenius parameters were calculated. Rate law was postulated taking into consideration of experimental results.

2,4 disubstitiuted furan derivatives (8Aâ8M) were prepared from furan-4-carboxylic acid ethyl ester (1). Antibacterial activity of new 2,4 di substituted furan derivatives was studied against Gram (+) and Gram (â) bacteria. 8F, 8E, 8D and 8J were found to be effective against Gram (â) bacteria whereas, 8A and 8L were effective against Gram (+) bacteria. Least MIC value was found as 100 µg/ml against Escherichia coli (for 8D and 8F), and Proteus vulgaris (for 8E and 8F). Antibacterial activity is correlated with different substituents. Products exhibited better antibacterial activities especially towards Streptococcus pyogenes, Proteus vulgaris, and Escherichia coli. Keywords: Pathogens, Antibacterial activity, Structure-activity relationship, Disubstitiuted furans, Synthesis

Kinetics of uncatalyzed and ruthenium(III) catalyzed oxidation of monoethanolamine by N-bromosuccinimide (NBS) has been studied in an aqueous acetic acid medium in the presence of sodium acetate and perchloric acid, respectively. In the uncatalyzed oxidation the kinetic orders are: the first order in NBS, a fractional order in the substrate. The rate of the reaction increased with an increase in the sodium acetate concentration and decreased with an increase in the perchloric acid concentration. This indicates that free amine molecules are the reactive species. Addition of halide ions results in a decrease in the kinetic rate, which is noteworthy. Both in absence and presence of a catalyst, a decrease in the dielectric constant of the medium decreases the kinetic rate pointing out that these are dipole—dipole reactions. A relatively higher oxidation state of ruthenium i.e., Ru(V) was found to be the active species in Ru(III) catalyzed reactions. A suitable mechanism consistent with the observations has been proposed and a rate law has been derived to explain the kinetic orders.

Role of added chloride ions on the shift of reaction pathway of oxidation of aromatic ketones (acetophenone, desoxybenzoin) by dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Participation of enolic and protonated forms of ketones in the rate determining steps is manifested from zero and first orders with respect to the oxidant in absence and presence of added chloride ions, respectively. Positive and negative effects of acid and dielectric constant on the reaction rate were observed. The observations deduce plausible mechanisms involving (i) rate-determining formation of enol from the conjugate acid of the ketone (SH+) in the absence of added chloride ions and (ii) rapid formation of molecular chlorine species from HOCl (hydrolytic species of DCICA) in the presence of added chloride ions, which then interacts with SH+ in a rate-determining step prior to the rapid steps of product formation. The order of Arrhenius parameters substantiate the proposed plausible mechanisms based on order of reactants both in presence and absence of added chloride ions.

Kinetics of ruthenium(III) catalyzed oxidation of biologically important sugar alcohols (myo-inositol, D-sorbitol, and D-mannitol) by dichloroisocyanuric acid was carried out in aqueous acetic acid—perchloric medium. The reactions were found to be first order in case of oxidant and ruthenium(III). Zero order was observed with the concentrations of sorbitol and mannitol whereas, a positive fractional order was found in the case of inositol concentration. An inverse fractional order was observed with perchloric acid in oxidation of three substrates. Arrhenius parameters were calculated and a plausible mechanism was proposed.

Effect of added chloride ions on kinetics and pathway of reaction between cyclic ketones (five to eight membered rings) and dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric acid medium. Formation of aliphatic dicarboxylic acids as the end products demonstrates the ring cleavage oxidation. Positive effect of acid and negative effect of dielectric constant on the reaction rate reveals a interaction between positive ion (oxidant in the form of H2OCl+) and dipolar substrate molecule. Zero and first orders by oxidant in absence and presence of added chloride ions illustrates the participation of substrate as enolic form of ketone and protonated ketone, respectively, in the rate determining steps. The observed order of reactivity of cyclic ketones (cyclohexanone > cyclooctanone > cyclopentanone > cycloheptanone) was explained on the bases of ring strain, change of hybridization and conformational considerations. The envisaged plausible mechanism based on order of reactants in presence and absence of added chloride ions was substantiated by the order of Arrhenius parameters.

In the oxidation of D-sorbitol and D-mannitol by potassium periodate in alkaline media, substrate inhibition was observed with both substrates, i.e., a decrease in the rate of the reaction was observed with an increase in the concentration of substrate. The substrate inhibition was attributed to the formation of stable complex between the substrate and periodate. The reactions were found to be first order in case of periodate and a positive fractional order with hydroxide ions. Arrhenius parameters were calculated for the oxidation of sorbitol and mannitol by potassium periodate in alkali media.

Polyethylene glycol-400 (PEG-400) has a spectrum of applications in pharmaceutical field. PEG-400 oxidation was carried out in alkaline medium by using potassium periodate as an oxidant. Rate of the reaction was found to be first order dependence on the oxidant concentration. In the studied range, substrate concentration didn't change the reaction rate. Increase of alkali concentration decreased the reaction rate and order of the reaction with respect to alkali was inverse fractional. Effect of temperature on reaction rate was studied and then Arrhenius parameters were calculated. A suitable rate law was proposed based on the observed experimental results.

Two simple, sensitive, selective, accurate and economical spectrophotometric methods (A and B) have been described in the present work for the determination of Nicergoline in bulk drug and pharmaceutical formulations (tablets). Methods - A/B are based on the formation of orange red / yellow colored ion-association complexes between Nicergoline and Tropaeolin ooo (TPooo) / Alizarine Red S (ARS) in acid medium followed by their extraction with chloroform, exhibiting absorption maxima at 490nm / 430nm, and obeying Beer's law in the concentration range of 2.5- 12.5µg/ml. Statistical analysis of the results of the proposed methods reveals high accuracy and good precision. The proposed methods could be successfully extended to the commercial pharmaceutical formulations containing Nicergoline.

Objectives To determine anthelmintic activity of the synthesized novel 1,2,3 – benzotriazole derivatives under ultrasonication in solvent free conditions. Methods Newer “1–(1H–benzo[d][1,2,3]triazole-1-carbonyl) derivatives” (5A–5P) were synthesized by using “1H–benzo[d][1,2,3]triazole” (1) as the starting material under ultrasonicated and solvent-free conditions. The resulting products were isolated and characterized by melting points and spectral studies. All the products were assayed for anthelmintic activity against Pheretima posthuma using albendazole and mebendazole as reference compounds. Results All the newer 1,2,3 – benzotriazole derivatives synthesized by ultrasound activation in solvent–free condition were obtained in moderate to good yields in the range of 71–82%. The data interpretation of the spectral values with reference to standard values confirmed the structures of the synthesized compounds. Out of the sixteen synthesized derivatives, four compounds (5B, 5F, 5J and 5N) showed anthelmintic activity in dose-dependent manner giving shortest time of paralysis and death with different concentrations of the derivatives. Among these four derivatives, 5J showed superior activity. Conclusion Out of the sixteen synthesized derivatives, four compounds (5B, 5F, 5J and 5N) containing p -nitrophenyl substituent attached to azo group of benzotriazole moieties exhibited equal or comparable anthelmintic activity with reference to albendazole. The superior activity of compound 5J might be due to attachment of additional p -nitrophenyl substituent to the cyano group.

UltraPerformance convergence chromatography (UPC2 ™) is a new category of separation science which utilizes the unrealized potential of the supercritical chromatography phenomenon. UPC2™ is a stand-alone, viable technique that is cost effective, sustainable, and uses green technology that lowers the use of organic solvents. Based on this advantage, we explored a simple and robust supercritical liquid-based UPC2 method in order to increase sample throughput and productivity to quantify the diastereomers of fulvestrant. The two isomers of fulvestrant were well separated on a chiral column (150 mm × 4.6 mm, I.D.) by applying a mixture of methanol and acetonitrile (9.5 : 0.5) as the co-solvent of the mobile phase of carbon dioxide (75%). The detection was carried out at 280 nm. We were able to achieve a three-fold reduction in retention with an isocratic mode as compared to the United States Pharmacopoeias (USP) normal phase method. This new method was validated in accordance with the ICH guidelines; it exhibited good intra- and inter-day accuracy, precision, and the results were linear over a range of 25% to 150% of the target concentration. The method could be successfully applied for the determination of the diastereomeric ratio of fulvestrant as an API and in fulvestrant injectable finished products.