http://nopr.niscair.res.in/handle/123456789/6007 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/6015 Title: Studies on complexation between urea and 18-crown-6 in aqueous solutions at 298.15K <br/> <br/>Authors: Tomar, Preeti <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="metricconverter"> Osmotic vapor pressure and density measurements have been made for binary aqueous urea solutions (0.1<i style="">m</i>-1<i style="">m</i>) and ternary aqueous solutions containing three different concentrations of 18-crown-6 (0.1, 0.2 and 0.5<i style="">m</i>) at 298.15K. The molal activity coefficients of urea, water and 18-crown-6 in binary as well as in ternary solutions have been calculated. Thermodynamic equilibrium constant, salting coefficient and molecular interaction parameters have been determined. The results are explained in terms of 1:4 stoichiometric complex formation with urea at the lowest concentration of 18-crown-6 having a small equilibrium constant value. At higher 18-crown-6 concentrations, water forms hydrogen bond with crown ring oxygen atoms and hydrophobic interaction between 18-crown-6 molecules outweighs the interaction of urea with 18-crown-6 molecules, resulting in salting out of urea molecules. </smarttagtype> <br/> <br/>Page(s): 1247-1250 http://nopr.niscair.res.in/handle/123456789/6014 Title: Intermolecular interaction studies of binary mixtures of a ketoester and carbonyl compounds. I: Excess volumes of binary mixtures of ethyl acetoacetate with aliphatic ketones at 298.15K <br/> <br/>Authors: Izonfuo, Welford-Abbey Lolo; Kemeakegha, Ayasen Jermaine <br/> <br/>Abstract: Density data on binary mixtures of ethyl acetoacetate and aliphatic ketones containing four to six carbon atoms have been obtained with a single capillary pyknometer at 298.15K over the entire range of solvent composition. Excess volumes of the binary mixtures, calculated from the density data, for the binary mixtures of ethyl acetoacetate with the straight chain ketones, butan-2-one and pentan-3-one are negative over the entire range of solvent composition. The negative excess volumes are attributed to volume reductions arising from the fitting of the ketone molecules having smaller molecular volumes into the ethyl acetoacetate molecules with larger molecular volumes. The excess volumes of the branched aliphatic ketones, 3-methylbutan-2-one and 4-methylpentan-2-one are negative in some regions of solvent composition and positive in other regions of solvent composition. The negative excess volumes in the binary mixtures of ethyl acetoacetate and the branched ketones are attributed to strong dipole-dipole interactions between unlike molecules while the positive excess volumes are attributed to a mutual loosening of dipole-dipole interactions between like molecules. <br/> <br/>Page(s): 1242-1246 http://nopr.niscair.res.in/handle/123456789/6013 Title: The selectivity of nucleobases in DNA binding by Ru(phenanthroline)₃complex <br/> <br/>Authors: Hazarika, P; Bezbaruah, B; Gogoi, A; Das, P; Medhi, O K; Medhi, C <br/> <br/>Abstract: Interaction ability of Ru(phenanthroline)₃ with various sites of nucleobases like guanine, adenine, cytosine and thymine has been investigated by <i style="">ab initio</i> quantum mechanical calculations. While the N7 of guanine is found to be a susceptible site for binding with Ru metal, the other sites of nucleobases can also bind with this metal centre. The O6 of guanine and O2 of cytosine can form more stable Ru coordinated complexes than N7 of guanine. Formation of bridged hydrogen bonds between polarized atomic sites of this complex and all the nucleobases (except thymine) has been observed. Such hydrogen bonds may also stabilize the complex better than the direct Ru coordinated complexes inside DNA. <br/> <br/>Page(s): 1235-1241 http://nopr.niscair.res.in/handle/123456789/6012 Title: Kinetic studies on effects of EDTA and surfactants on reduction of vanadium(V) to vanadium(IV) in sulphuric acid medium <br/> <br/>Authors: Mishra, A P; Khan, Raju; Pandey, Ravi Ranjan <br/> <br/>Abstract: Reduction kinetics of vanadium(V) to vanadium(IV) by EDTA and effects of surfactant have been studied using thiourea as a reductant at 40±1°C in acidic medium at 350 nm. UV-vis and ESR spectral techniques have been used to confirm the reduction product of vanadium(V). Electronic absorption spectra of the reaction products suggest the formation of aqua vanadium(IV) and vanadium(IV)-EDTA complex in the absence and presence of EDTA, respectively. The oxidation of thiourea by vanadium(V) has also been studied in the presence of surfactants. The anionic sodium dodecyl sulphate and non-ionic TX-100 surfactants catalyze the reaction whereas the cationic surfactant, cetyltrimethylammonium bromide, has no effect. The single electron sequence is confirmed by the formation of vanadium(IV) aqua ion. The experimentally determined intermediate complex formation constant<i style="">, K</i>_es is 34 mol^-1dm³. <br/> <br/>Page(s): 1228-1234