NOPR Collection:

Molecular topology 27: A Schultz-type index based on the Wiener matrix

2017-04-19T10:09:56Z

Title: Molecular topology 27: A Schultz-type index based on the Wiener matrix Authors: Diudea, Mircea V; Pop, Corina M Abstract: A novel Schultz analogous index, denoted WI, is defined on the basis of Wiener matrix and the matrix algebra initiated by Schultz. It is compared with the well known indices such as molecular topological index, MTI, Wiener index, W, hyper-Wiener index, R, and the recently introduced indices DI and HI, within the set of octane isomers and other selected graphs. Page(s): 257-261

Reactions of ethene over silica, -alumina, YBa₂Cu₃O_6.9 perovskite and ZSM-5 zeolite: Thermal versus catalytic processes

2017-04-19T10:08:28Z

Title: Reactions of ethene over silica, -alumina, YBa₂Cu₃O_6.9 perovskite and ZSM-5 zeolite: Thermal versus catalytic processes Authors: Shete, B S; Belapurkar, A D; Kamble, V S; Gupta, N M Abstract: The reaction products formed during the flow of ethene at temperatures above 500°C over silica, YBa₂Cu₃O_6.9 perovskite and through an empty quartz reactor have been found to be similar to those obtained during its reaction over ZSM-5 zeolite and -alumina samples at lower temperatures. The prominent reaction products consisted of methane, propane, butane, propene, butene, pentene, methylpentane, cyclohexene, hexene, benzene and toluene. The product distribution, however, varies with the nature of the sample and the reaction temperature. The addition of oxygen in ethene leads to higher yields of almost all the reaction products, particularly at sample temperatures above 500°C. The enhancement increases progressively with the increase in oxygen content, the effect being more pronounced on the lower hydrocarbons containing odd number of carbon atoms, e.g., propene and pentene. It is suggested that at reaction temperatures above 500°C, the free radicals such as CH₃, CH₂ and CH, formed during thermal dissociation or self hydrogenation of C₂H₄ molecules, help in the hydrocarbon chain growth. The formation of the highly unstable epoxy species, viz. in the presence of oxygen facilitates this process. In the case of catalytic reactions over ZSM-5 or -alumina, the lewis acid sites rather than the Bronsted hydroxyl groups are proposed to be the reaction sites where ethene adsorbed in the form of a cyclic complex transforms to the similar transient surface species at lower temperatures. Page(s): 262-269

Transfer energetics of some nucleosides in aqueous mixtures of urea and glycerol

2017-04-19T09:48:07Z

Title: Transfer energetics of some nucleosides in aqueous mixtures of urea and glycerol Authors: Ganguly, Sonali; Kundu, Kiron K Abstract: Standard free energies (G) and entropies (S) of transfer of some nucleosides viz. adenosine (ado), guanosine (guo) and xanthosine (xao) from water to aqueous mixtures of urea (UH) and glycerol (GL) have been evolved from solubilities measured at different temperatures. The observed G- composition profiles show increasing stabilization for the nucleosides in both the cosolvent systems. The TS-composition profiles are, however, complicated. So, after the elimination of various interaction effects, viz. cavity, dipole-dipole, dipole-induced dipole and dispersion interactions, the results have been discussed in the light of the hydrophilic-hydrophobic hydration effect. The solvation behaviour of the nucleosides in UH-water and GL-water mixtures help understand the relative stability of the double stranded nucleic acid helix in these. two cosolvent systems. Page(s): 270-280

Electrochemical oxidation of 2-mercaptobenzoxazole

2017-04-19T09:42:04Z

Title: Electrochemical oxidation of 2-mercaptobenzoxazole Authors: Goyal, Rajendra N; Verma, Madhu Shri Abstract: Electrochemical oxidation of 2-mercaptobenzoxazole has been studied in the phosphate buffers of pH 2.5-10.3 at solid electrodes. In the entire pH range a well-defined oxidation peak (I_a) was observed. The peak potential of this peak is linearly dependent on pH and the E_p-pH plot shows a break around pH 7.8, corresponding to the pk_a of the species. At pH ≥ 7.0 an additional oxidation peak (II_a) has been noticed. The electrode process is found to involve adsorption complications at PGE and the change in E_p with log v indicated radical radical coupling. The products of oxidation have been separated and characterized by using m.p., ¹H NMR and mass spectra. Page(s): 281-287

NOPR Collection:

Molecular topology 27: A Schultz-type index based on the Wiener matrix

Reactions of ethene over silica, -alumina, YBa2Cu3O6.9 perovskite and ZSM-5 zeolite: Thermal versus catalytic processes

Transfer energetics of some nucleosides in aqueous mixtures of urea and glycerol

Electrochemical oxidation of 2-mercaptobenzoxazole

Reactions of ethene over silica, -alumina, YBa₂Cu₃O_6.9 perovskite and ZSM-5 zeolite: Thermal versus catalytic processes