Wyniki wyszukiwania - BazTech

1

Kinetics and mechanism of meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate

Kungumathilagam D., Karunakaran K.

Polish Journal of Chemical Technology

|

2013

|

Vol. 15, nr 2

107–111

EN

Developing catalyst is very significant for biologically important reactions which yield products, used as drugs. Mechanistic study on meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate in aqueous acetic acid medium have been carried out. The reaction follows a fractional order with respect to substrate and catalyst. The order with respect to oxidant was found to be one. Increase in the percentage of acetic acid and increase in the concentration of [H+] decreased the rate. The reaction fails to initiate polymerization, and a radical mechanism is ruled out. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations has been proposed. Significant catalytic activity is observed for the reaction system in the presence of TPP.

2

Development and application of stability-indicating HPLC method for the determination of nevirapine and its impurity in combination drug product

Navaneethan G, Karunakaran K., Elango K. P

Acta Chromatographica

|

2012

|

Vol. 24, no. 4

575--587

EN

A stability-indicating reversed-phase high-performance liquid chromatography method has been developed and validated for the estimation of nevirapine and its impurity, namely the related compound A and the related compound B in combination drug product. The separation was carried out on SUPELCOSIL ABZ (150 mm × 4.6 mm, 5 µm) column. Tablet was admitted to the stress conditions of acid, base, peroxide, thermal, humidity, and photolytic degradation. The degradation products were well resolved from nevirapine, and its impurities peaks and the peak homogeneity of compound were obtained using photo diode array detector, hence proving the stability-indicating nature of the method. Moreover, to prove the selectivity of the method, individual lamivudine, zidovudine, and their main impurities were injected. The developed method was linear for nevirapine from 120 to 360 µg mL-1, and the linear regression obtained was >0.999. Recovery data were in the range 98.2–101.5%. The limit of quantification for related compound A and related compound B was found to be 0.02%. The proposed method was validated according to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines and proved suitable for stability testing and quality control of these drugs in pharmaceutical preparations.

3

Kinetic, Equilibrium and Thermodynamic studies on the removal of Cr(VI) by activated carbon prepared from Cajanus Cajan(L) Milsp seed shell

Thamilarasu P., Kumar Vijaya G., Tamilarasan R., Sivakumar V., Karunakaran K.

Polish Journal of Chemical Technology

|

2011

|

Vol. 13, nr 4

1-7

EN

This paper presents the feasibility of the removal of hexavalent chromium ions from aqueous solutions by using activated carbon prepared from Cajanus Cajan(L) Milsp. It was carbonized and activated by treating it with concentrated sulfuric acid followed by heating for 5 h at 500oC. Batch adsorption experiments were carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data fi tted well to the Freundlich isotherm. The thermodynamic parameters such as ΔHo, ΔSo, and ΔGo were calculated, which indicated that the adsorption was spontaneous and endothermic in nature. The adsorbent used in this study was characterized by FT-IR and SEM before and after the adsorption of metal ions. The results indicate that Cajanus Cajan(L) Milsp can be employed as a low cost alternative and commercial adsorbents in the removal of chromium (VI) from water and waste water.

4

Kinetics of oxidation of phenoxyacetic acids by quinolinium fluorochromate

Karunakaran K.

Polish Journal of Chemistry

|

1998

|

Vol. 72, nr 5

916-924

EN

The kinetics of oxidation of twenty one phenoxyacetic acids by quinolinium fluorochromate have been studied in binary solvent mixtures. Acrylonitrile has no effect on the rates of oxidation in dipolar protic solvent but in a aprotic solvent it decreases the oxidation rates. In both solvent systems there exists an equilibrium prior to the rate limiting step, followed by irreversible decomposition of the complex. The calculated rate constants correlate well with Hammett delta values. Suitable mechanisms have been proposed.