Showing papers by "Anju Chadha published in 2011"

Kinetic Studies of Base-Catalyzed Transesterification Reactions of Non-edible Oils To Prepare Biodiesel: The Effect of Co-solvent and Temperature

Abstract: The non-edible oils of mahua and jatropha were transesterified using methanol and 1 wt % KOH as the catalyst. The effect of co-solvent and the kinetic study of the transesterification of mahua oil is being reported here for the first time. Kinetics, modeled as a single-step reaction, revealed that the order of the reaction is 2 with respect to the triglyceride concentration and 1 with respect to the methanol concentration in both oils. In the presence of co-solvent, tetrahydrofuran (THF), methanolysis of mahua oil resulted in the increase of the rate constants from 0.08 to 1.17 L2 mol–2 min–1 at 28 °C and from 0.43 to 3.18 L2 mol–2 min–1 at 45 °C. The corresponding values for jatropha oil were found to be 0.50 and 2.76 L2 mol–2 min–1 at 28 °C and 1.26 and 4.56 L2 mol–2 min–1 at 45 °C.

One-pot synthesis of enantiomerically pure 1, 2-diols: asymmetric reduction of aromatic α-oxoaldehydes catalysed by Candida parapsilosis ATCC 7330

Abstract: A facile and simple one-pot method was developed to produce a series of optically active (S)-1-phenyl-1,2-ethanediols with good yields (up to 70%) and high enantiomeric excess (>99%) via asymmetric reduction of various substituted aromatic α-oxoaldehydes using Candida parapsilosis ATCC 7330.

Potentiometric estimation of blood analytes—triglycerides and urea: Comparison with clinical data and estimation of urea in milk using an electrolyte–insulator–semiconductor–capacitor (EISCAP)

Abstract: A modified electrolyte–insulator–semiconductor–capacitor (EISCAP) developed in-house was used for the determination of triglycerides and urea in blood, in addition to urea in milk. The sensitivity of the sensor was 55 ± 0.5 mV per unit change of pH. The EISCAP was optimized to operate at 25 °C in 0.25 mM phosphate buffer (pH 6), 1 M KCl and 1 mg lipase for triglycerides and in 1 mM Tris–HCl buffer (pH 7.4), 0.5 M KCl and 0.5 U urease for urea. Comparisons of the results obtained from the developed biosensor and clinical records gave correlation coefficients of 0.979 and 0.974 for blood triglycerides and blood urea respectively. Similarly, estimation of milk urea determined using the sensor in comparison with the spectrophotometric method gave a correlation coefficient of 0.992. The sensor gave reproducible and reliable results up to six months.

Synthesis of both enantiomers of ethyl-4-chloro-3-hydroxbutanoate from a prochiral ketone using Candida parapsilosis ATCC 7330

Abstract: Candida parapsilosis ATCC 7330 when grown in a medium containing glycerol reduced ethyl-4-chloro-3-oxobutanoate to ( R )-ethyl-4-chloro-3-hydroxybutanote (ee >99%, yield: 94%) while glucose and sucrose grown cells yielded ( S )-ethyl-4-chloro-3-hydroxybutanote (ee >99%, yield: 96%). The activity of ethyl-4-chloro-3-oxobutanoate reductase was higher in glucose-grown cells (160 U/g protein) when compared to sucrose (158 U/g protein) and glycerol (22 U/g protein). Both the enantiomers of ethyl-4-chloro-3-hydroxybutanoate (ee >99%) can thus be obtained using Candida parapsilosis ATCC 7330 by altering the carbon source in the growth medium.

Candida parapsilosis ATCC 7330 can also deracemise 1-arylethanols

Abstract: Candida parapsilosis ATCC 7330 grown using different culture conditions (inoculum size 4% (v/v), inoculum age 12 h, and harvest time 14 h) from those previously reported (inoculum size 2% (v/v), inoculum age 24 h, and harvest time 44 h) successfully deracemised racemic 1-arylethanols and 4-phenyl-2-butanol to the (R)-enantiomer (ee up to >99%). The deracemisation of racemic 1-aryl ethanol proceeds via (i) enantioselective oxidation of (S)-enantiomer followed by (ii) reduction of the ketone formed to give the racemic alcohol which gets kinetically resolved thus enriching for the (R)-enantiomer from the racemate. This is the first report on the deracemisation of 1-arylethanols using Candida parapsilosis ATTC 7330 via dynamic kinetic resolution.

Photophysical investigation of microenvironment in glycerol based dansylated polyether dendrons

Abstract: Photophysical studies of four generations of polyglycerol dendrons with isopropylidene end groups and dansyl moiety as a fluorophore attached at the focal point were carried out. All the four generations showed similar behaviour in their absorption transitions but the emission maximum for all generations of dendrons showed strong dependence on the solvent polarity. The solvatochromic shift of emission maximum showed linearity in the Lippert–Mataga plot, indicating the dominant importance of general solvent effect in all generations of dendrons. Photophysical parameters such as fluorescence quantum yield, fluorescence lifetime and radiative decay rate constant showed solvent polarity dependence. The detailed photophysical study reveals that due to the increased influence of the repeating dendron units of the higher order dendrons on the dansyl microenvironment, it becomes less and less influenced by the solvent.