NOPR Collection:

Some graph-theoretic studies on aniline and p-phenylenediamine-like systems in HMO formalism

Sun, 01 Jul 1990 00:00:00 GMT

Title: Some graph-theoretic studies on aniline and p-phenylenediamine-like systems in HMO formalism Authors: Mukherjee, A K; Datta, K K Abstract: By studying the signs of the terms in the characteristic polynomials (CP) and their derivatives of the molecular graph, energy-level patterns and the upper and lower bounds to the smallest and largest positive eigenvalues have been determined for aniline- and p-phenylenediamine-like systems. The dependence of the HMO energies of the highest occupied molecular orbitals on the heteroatom Huckel parameters, represented by h and k, has been ascertained. The results are in agreement with the trends in the actually computed energy values compiled by Coulson and Streitwieser. The derived modes of dependence of the HOMO energy on h and k correctly predict the trends in electron donor properties of the systems under study with variation in electronegativities of the hetero atoms. Page(s): 613-617

Spectroscopic and molecular mechanics study of the conformational properties of methyl cyanoacetate and ethyl cyanoacetate

Sun, 01 Jul 1990 00:00:00 GMT

Title: Spectroscopic and molecular mechanics study of the conformational properties of methyl cyanoacetate and ethyl cyanoacetate Authors: Prasad, R; Mishra, Y K; Gupta, R K Abstract: Infrared spectra of methyl cyanoacetate and ethyl cyanoacetate have been recorded in different solvents of varying polarity in the region 4000-600 cm^-1 along with laser Raman spectra of the liquid samples of these compounds in the region 4000-50 cm^-1. Existence of conformers has been confirmed in both the molecules on the basis of splitting of some of the bands and CNDO/2 and molecular mechanics computations. Normal coordinate analysis of both the molecules has been carried out and the force constants thus obtained have been employed to compute the energies of different conformers by the method of molecular mechanics. The computed conformational energy of methyl cyanoacetate is in close agreement with the experimental values. It has been concluded that for these molecules the cis conformers are most stable. The energy difference between gauche-trans and cis-trans conformers of ethyl cyanoacetate is computed to be 1.0 kcal mol^-1. Page(s): 618-623

Adsorption and reactivity of thiophene on promoted molybdena and tungsta systems

Sun, 01 Jul 1990 00:00:00 GMT

Title: Adsorption and reactivity of thiophene on promoted molybdena and tungsta systems Authors: Alias, M O; Srinivasan, V Abstract: The interaction of thiophene with Co and Ni promoted molybdena and tungsta catalyst systems has been studied with a view to interpreting surface activity for hydrodesulfurisation reaction. Gas-solid chromatography has been used for the study of adsorption of thiophene on catalysts. Adsorption isotherms and heat of adsorption have been evaluated. It is found that molybdena catalysts have good thiophene adsorption properties as compared to tungsta catalysts. The better thiophene adsorption properties obtained for molybdena catalyst is consistent with higher desulfurisation activities observed for these catalysts. Ni-Mo system is the most suitable catalyst system for hydrodesulfurisation reaction. Page(s): 624-630

Electrical and magnetic properties of poly(N-ethylaniline)

Sun, 01 Jul 1990 00:00:00 GMT

Title: Electrical and magnetic properties of poly(N-ethylaniline) Authors: Borkar, AD; Gupta, Mool C Abstract: Poly(N-ethylaniline) has been obtained by peroxodisulphate oxidation of N-ethylaniline in aqueous sulphuric acid solution. TGA shows an initial mass loss due to loss of water molecules; the activation energy and pre-exponential factor for thermal decomposition in air have been found to be 125 kJ mol^-1 and 1.4 x 10⁹s^-1 respectively. The polymer is paramagnetic and X-ray diffraction data show it to be an amorphous powder. The electrical conductivity has been measured at temperatures from 303 to 433 K. From the plot of log σ vs 1/T, the activation energy of conductivity has been found to be 0.078 eV. It is suggested from the temperature dependence of the conductivity and magnetic moment that the conduction mechanism is possibly small polaron hopping conduction. Page(s): 631-634