http://nopr.niscair.res.in/handle/123456789/517 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/584 Title: Synthesis and characterisation of Sb₂Zn₂Cl₄ (OPri)₆, MSb₂Cl₂ (OPri)₆ (M = Be, Mg, Zn), and M₂Ti₄Cl₄(OPri)₁₆ (M = Mg, Zn) <br/> <br/>Authors: Shahani, Jayshree; Singh, Anirudh <br/> <br/>Abstract: Reactions of MCl2 (M = Be, Mg, Zn) with Sb(OPri)₃ and Ti(OPri)₄ in desired molar ratios in benzene afford structurally interesting derivatives of the types MSb₂Cl₂ (OPri)₆ (M Be(1), Mg(2), Zn(3)), Sb₂Zn₂Cl₄(OPri)₆(4), M₂Ti₄Cl₄(OPri)₁₆ (M = Mg(5), Zn(6)). All these derivatives have been characterized by elemental (Be, Mg, Zn, Sb, Cl, Ti) analyses, isopropoxo groups determinations, molecular weight measurements, and spectro-scopic studies. <br/> <br/>Page(s): 55-57 http://nopr.niscair.res.in/handle/123456789/557 Title: Enantioseparation condition of D,L-tryptophan using ligand exchange chromatography <br/> <br/>Authors: Yan, Hongyuan; Row, Kyung Ho <br/> <br/>Abstract: Chiral recognition mechanism and enantioseparation conditions of tryptophan enantiomers using ligand exchange chromatography are reported here. The effect of different kinds and concentration of ligands, bivalent copper ion, organic modifier, pH of mobile phase, and temperature on enantioseparation has been evaluated. The results show that the enantioselectivity is strongly affected by the pH and the ligand concentration. Under the optimum condition, baseline separation of the two enantiomers has been obtained on a C₁₈ column with a resolution of 3.42 in less than 30 min using methanol-water solution (20:80 v/v) as mobile phase containing 3.0 mmol•L⁻¹ L-phenylalanine and 0.5 mmol•L⁻¹ copper sulphate. Thermodynamic data (ΔΔH and ΔΔS) obtained by Van’t Hoff plots reveal that the enantioseparation is an enthalpy-controlled process. The mechanism of chiral discrimination is based on the stabilities of the copper(II) binary complexes and their ternary diasteremeric complexes with amino acids formed in solution and stationary phase. The proposed method has been successfully used for the quality evaluation of tryptophan enantiomers. <br/> <br/>Page(s): 75-80 http://nopr.niscair.res.in/handle/123456789/555 Title: Determination of the polyacid dissociation constants of glycyrrhizic acid <br/> <br/>Authors: Zeng, Chun-Xiang; Hu, Qin <br/> <br/>Abstract: Determination of the three stepwise dissociation constants of glycyrrhizic acid in water by potentiometric titration method is described here. The experimental data have been processed with a stepwise linear regression and simultaneous equations algorithm. The three dissociation constants of glycyrrhizic acid assayed by the proposed method are 3.98 (pKa₁), 4.62 (pKa₂) and 5.17 (pKa₃), respectively. The distribution of the different charged ions of glycyrrhizic acid under different pH values has been simulated with Microsoft Excel software. The results are accurate and useful for further pharmacological and pharmacal studies of glycyrrhizic acid. <br/> <br/>Page(s): 71-74 http://nopr.niscair.res.in/handle/123456789/554 Title: Excess molar volumes and viscosity deviations of binary liquid mixtures of N-methylacetamide with ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate <br/> <br/>Authors: Boodida, Sathyanarayana; Bachu, Ranjith Kumar; Tangeda, Savitha Jyostna; Nallani, Satyanarayana <br/> <br/>Abstract: The values of density and viscosity for the binary liquid mixtures of N-methylacetamide with aliphatic esters (ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate) have been measured over the entire range of composition at T = 303.15 to 318.15 K. Using these data, excess molar volumes (VE) and deviations in viscosity (Δη) have been calculated. The results have been correlated with the Redlich-Kister type polynomial equation to derive the binary coefficients and standard errors. <br/> <br/>Page(s): 66-70