A mild, efficient and improved protocol for the synthesis of novel indolyl crown ethers, di(indolyl)pyrazolyl methanes and 3-alkylated indoles using H4[Si(W3O10)3]

Efficient electrophilic substitution reactions of indoles with various aldehydes proceed smoothly in acetonitrile using heteropoly acid (H₄[Si(W₃O₁₀)₃]) to afford the corresponding new indolyl crown ethers and di(indolyl)pyrazolyl methanes. H₄[Si(W₃O₁₀)₃] is also found to catalyze the Michael addition of indoles to ,β-unsaturated compounds for the synthesis of 3-alkylated indoles.     

Surface enhanced Raman scattering studies of acetophenone on colloidal silver particles

Intense Raman scattering by acetophenone molecules adsorbed on colloidal silver particles is reported. Greater enhancement is observed for the ring breathing and ring stretching vibrations. The orientation determination analysis shows that the adsorption of acetophenone molecule is neither through its co-ordinating site nor through itsπ-orbital system and there is no strong chemical interaction. However significant intensity enhancement for several vibrations suggests that the contribution is from classical electromagnetic field on the rough surface.     

Nonnegativity of principal minors of generalized inverses of P0-matrices

We derive a necessary and sufficient condition under which a reflexive generalized inverse of a singular P₀-matrix is again a P₀-matrix. Simpler conditions are obtained when the rank of the matrix is n?1, where n is the order of the matrix. We then consider the application of these results to singular M-matrices of order n and rank n?1. In particular, for this case we prove that the Moore-Penrose inverse is a P₀-matrix.     

7-Cis isomers of retinal via 7-cis- and 7,9-dicis-β-C18-tetraene ketones : New geometric isomers of vitamin A and carotenoids—I

Based catalyzed condensation of 7-cis- or 7,9-dicis-β-ionylideneacetaldehyde with acetone gave either 7-cis or 7,9-dicis-β-C₁₈-tetraene ketone. Reaction of the tetraene ketone mixture with diethyl cyanomethylphosphonate gave a mixture of 4 isomers of retinonitrile, all believed to have the 7-cis geometry. Partial redution of the retinonitrile mixture with di-isobutylaluminum hydride gave a mixture of retinal isomers. Repeated column chromatography resulted in partial separation of the retinal isomers. Based on NMR data the geometry of the isomers prepared are believed to be 7-cis, 7,13-dicis, and 7,9,13-tricis.     

Synthesis and properties of adenylate trimers A2′p5′A2′p5′A,A2′p5′A3′p5′A and A3′p5′A2′p5′A

Triadenylates with (2′-5′)(2′-5′) and mixed (2′-5′)(3′-5′) and (3′-5′)(2′-5′) linkages respectively were synthesized via the phosphotriester approach followed by deblocking of the fully protected intermediates. The isomeric trimers were characterized by NMR- and CD-spectra and show very similar hypochromicity effects.     

Leptodermous expansion of nuclear ground state energies and the anomaly in the nuclear curvature energy

The leptodermous expansion of the total ground state energy of a nucleus into volume, surface, curvature and gauss curvature contributions has been studied starting from a semi-classical energy density formalism of extended Thomas Fermi type. A numerical procedure was used to obtain the surface energy and curvature energy contributions from surface moments of energy density profilesH(r) for a sequence of nuclei withN=Z and neglecting the coulomb interaction for the three Skyrme forces. A transition to the liquid drop model type expansion in increasing powers ofA ^−1/3 is then made, taking into account the dependence of the central density and the surface structure on the mass of the nucleus. It is found that there is no inconsistency between the curvature contribution to the total energy in the leptodermous expansion and theA ^−1/3 term contribution in the liquid drop model expansion. It has been shown that the earlier apparent anomaly between the above two methods arises due to the use of semi-infinite approximation and the mass dependence of the central density and the surface structure of finite nuclei.     

A novel study of charged carbon clusters using a tandem Van de Graaff accelerator

A conventional tandem Van de Graaff accelerator is used to produce charged carbon cluster beams. The unique capability of the method for studying highly charged clusters unaccessible to other methods of producing cluster beams is demonstrated.