Showing papers by "Anju Chadha published in 2004"
TL;DR: In this article, the transesterification of MG obtained from crude Pongamia oil was achieved with methanol in the presence of KOH as the catalyst, and a MG/methanol ratio of 1∶10 was used at different temperatures (30, 45, 55, and 60°C).
Abstract: The kinetics of the transeterification of vegetable oil is known to follow a three-step reaction mechanism. The third step involves the transesterification of MG. In this study, the transesterification of MG obtained from crude Pongamia oil was achieved with methanol in the presence of KOH as the catalyst. A MG/methanol ratio of 1∶10 was used at different temperatures (30, 45, 55, and 60°C). 1H NMR was used to monitor the progress of transesterification. The study revealed that the kinetics of this reaction followed a reversible second-order model, with a good fit obtained for all temperatures except 30°C. This result is explained as arising out of the importance of transport effects at low temperatures. The forward rate constant increased with an increase in temperature, whereas the reverse rate constant showed a decreasing trend, suggesting that the proposed reverse reaction was not an elementary step.
65 citations
TL;DR: In this paper, aromatic β-hydroxy acid esters were found to undergo deracemisation using whole cells of Candida parapsilosis, and conditions for the deracemeisation reaction were optimised where ∼75% isolated yield and >95% enantiomeric excess of the product was achieved.
Abstract: Aromatic β-hydroxy acid esters were found to undergo deracemisation using whole cells of Candida parapsilosis. The conditions for the deracemisation reaction were optimised where ∼75% isolated yield and >95% enantiomeric excess of the product was achieved. The effect of electron donating as well as electron withdrawing groups present in the standard substrate, ethyl 3-hydroxy 3-phenyl propionate was studied to establish the generality of the reaction. The enantiomeric excess of the product remains high (>95%) irrespective of the different substituents in the para position but substitution at the ortho position obstructs the process. Similarly, ethyl and methyl esters of the standard substrate undergo deracemisation reaction giving high ee of the product, but the benzyl ester of the standard substrate did not undergo deracemisation.
44 citations
TL;DR: The absolute configuration of enantiomerically pure ethyl 2-hydroxy-4-(p -methylphenyl)but-3-enoate obtained by the reduction of the corresponding keto ester was assigned by 1 H NMR using Mosher's method.
Abstract: Enantioselective bioreduction of alkyl 2-oxo-4-arylbutanoates and 2-oxo-4-arylbut-3-enoates mediated by Candida parapsilosis ATCC 7330 resulted in the formation of the corresponding ( S )-2-hydroxy compounds in high enantiomeric excesses (93–99%) and good isolated yields (58–71%). The absolute configuration of enantiomerically pure ethyl 2-hydroxy-4-( p -methylphenyl)but-3-enoate obtained by the reduction of the corresponding keto ester was assigned by 1 H NMR using Mosher’s method.
43 citations
TL;DR: A highly enantioselective preparation of various 4-aryl-2-hydroxy but-3-enoic carboxylic acid esters from the corresponding 4-phenyl-2,keto but- 3-enoics mediated by plant cell cultures of Daucus carota under mild and environmentally benign conditions in aqueous medium is described.
Abstract: A highly enantioselective preparation (92–99% enantiomeric excess, 100% conversion) of various 4-aryl-2-hydroxy but-3-enoic carboxylic acid esters from the corresponding 4-phenyl-2-keto but-3-enoic acid esters mediated by plant cell cultures of Daucus carota under mild and environmentally benign conditions in aqueous medium is described.
32 citations
01 Jan 2004
TL;DR: In this article, a potentiometric biosensors with silicon for the estimation of triglycerides and urea based on enzymatic reactions is reported, which shows a shift in the measured CV with changes in the pH of the electrolyte.
Abstract: We report fabrication of potentiometric biosensors with silicon for the estimation of triglycerides and urea based on enzymatic reactions. The sensor is an Electrolyte–InsulatorSemiconductor capacitor (EISCAP) that shows a shift in the measured CV with changes in the pH of the electrolyte. Enzyme mediated biological reactions involve changes in the pH of the electrolyte and an EISCAP can be effectively used for detection of biological compounds. Optimization of the conditions for the enzymatic reaction and calibration of the sensor are included. Effect of replacing silicon with porous silicon is discussed.
1 citations