Presence Of Bonds Research Articles

Synthesis and Single Crystal X-ray Studies of Cyclic Te(IV) Diiodide

The cyclic tellurium(IV) diiodide, 2-Methyl-1,1-diiodo-1-telluracyclopentane, was prepared in good yields at room temperature by the incorporation of tellurium powder across Carbon–Iodine bond in presence of sodium iodide and acetone. The cyclic tellurium(IV) diiodide compound has been established by proton and 13carbon NMR spectroscopy along with elemental analysis. This compound was further characterized by 125Te NMR in DMSO. Molecular structures of cyclic tellurium(IV) diiodide was also established by single-crystal X-ray studies. In solid-state, molecular structures of cyclic tellurium(IV) diiodidepossess scarcely observed Te…I secondary bonding interactions (SBIs) and two molecule are co-crystallized. Both molecules are interconnected with each other by Te…I secondary bonding interactions. The five-membered rings acquire a twist-boat shape structure. Observed C–Te–C bond angles for molecule A, and molecule B are 85.0(1)°& 85.4(2)° respectively. Similarly observed, I–Te–I bond angles for both molecule A & B are 174.5(1)°&174.2(1)° respectively.

Designing of a New Heterogeneous Polymer Supported Naphthyl-Azo Iron Catalyst for the Selective Oxidation of Substituted Methyl Benzenes

A new and interesting heterogeneous iron-anchored naphthyl-azo catalyst (PS-Fe-NAPA) has been designed using aminopolystyrene and 2-nitrosonaphthol followed by loading iron in the naphthyl-azo complex. The prepared polymer supported material has been well characterized by FE-SEM, EDAX, TGA analysis, UV–Vis, FTIR, AAS, and elemental analysis. Iron-anchored naphthyl-azo complex exhibited excellent catalytic activity for the selective oxidation of toluene and substituted toluenes containing inactive benzylic C–H bonds in presence of mild oxidant hydrogen peroxide. Additionally, PS-Fe-NAPA complex is highly recyclable up-to six times without loss of its significant catalytic efficiency.

Behavior of potential energy surface of C–X bonds in presence of solvent and external electric field: A DFT study

The effect of external perturbations, namely solvent and external electric field on potential energy surface (PES) and bond dissociation energy of C–X (X[Formula: see text]F, Cl, Br, N, O) bonds has been studied in the light of density functional theory (DFT). The study reveals that presence of solvent as well as external electric field changes the curvature of the PES significantly. Bond dissociation energy significantly drops in presence of both the external perturbation.

First principles study of the structural, electronic and optical properties of crystalline o-phenanthroline

In a comprehensive study, structural properties, electronic structure and optical response of crystalline o-phenanthroline were investigated. Our results show that in generalized gradient approximation (GGA) approximation, o-phenanthroline is a direct bandgap semiconductor of 2.60 eV. In the framework of many-body approach, by solving the Bethe–Salpeter equation (BSE), dielectric properties of crystalline o-phenanthroline were studied and compared with phenanthrene. Highly anisotropic components of the imaginary part of the macroscopic dielectric function in o-phenanthroline show four main excitonic features in the bandgap region. In comparison to phenanthrene, these excitons occur at lower energies. Due to smaller bond lengths originated from the polarity nature of bonds in presence of nitrogen atoms, denser packing, and therefore, a weaker screening effect, exciton binding energies in o-phenanthroline were found to be larger than those in phenanthrene. Our results showed that in comparison to the independent-particle picture, excitonic effects highly redistribute the oscillator strength.

ChemInform Abstract: Chemo‐Controlled Cross‐Coupling of Di(hetero)aryl Disulfides with Grignard Reagents: C—C vs.C—S Bond Formation.

AbstractThe protocol for the chemoselective coupling reaction affords either a C—S bond in presence of ferrocene catalyst or the formation of a C—C bond in presence of palladium acetate catalyst.

Rhodamine based dual probes for selective detection of mercury and fluoride ions in water using two mutually independent sensing pathways

New rhodamine based molecules have been designed as dual probes for the ppb-level selective detection of Hg(2+) and F(-) ions in aqueous medium at physiological pH 7.4. The probes have been designed in such a way to utilize both the properties of the metal ion induced 'turn-on' detection mechanism of the spirolactam ring opening of the rhodamine moiety and the reaction based cleavage of the O-silyl bond in presence of the fluoride ion. The probes have been synthesized conveniently by coupling rhodamine hydrazone with O-silyl protected mono- and di-hydroxybenzaldehydes. Both the probes showed a 'turn-on' detection of the fluoride ion due to the cleavage of the O-silyl bond upon treatment with the added F(-) ion. However, the probes showed selective 'turn-on' detection of Hg(2+) ion by opening of the spirolactam ring. The two detection mechanisms worked in isolation and hence the corresponding spectral responses appeared completely independent of each other. The presence of Hg(2+) in solution induced generation of an intense pink color with bright green fluorescence emission. In contrast a deep yellow color with yellow fluorescence was observed upon addition of the fluoride ion to the probe solution. Two different mechanisms of interactions have been proposed on the basis of (1)H-NMR, IR and mass spectrometric studies. Thus, using a single probe the selective sensing of two different ions could be achieved in aqueous medium well below their permitted limit of detection.

Ab initio study of defective chains in icosahedral boron carbide B4C

Two kinds of chain defects have been studied in icosahedral boron carbide, with the density functional theory: (i) The boron chain vacancy at the center of the chain, modeled by (B11Cp)C–V–C, is found to be metastable at low pressure, and to transform to (B11Cp) C–C with a discontinuous variation of volume at high pressure. (ii) The formation of a carbon–carbon bond in the defective chain, modeled by (B11Cp)C–C, is found to be metastable both at low and high pressure. The energy barrier for the formation of a carbon–carbon bond in presence of an interstitial boron atom is shown to be very high.

Competition between aggregate formation and conformational changes of polyaniline in binary solutions studied by electronic absorption spectroscopy

Aggregation and conformational changes of undoped and protonated doped forms of polyaniline (PANI) in the emeraldine oxidation state were studied in solutions of homogeneous organic solvents and their mixtures with water, using optical absorption spectroscopy. It was found that the conformational changes accompany both an increase of concentration of the undoped PANI in the solution and addition of water to the solution. The first process gives rise to an increase in molar extinction coefficient, while the second to their decrease. Expanded-coil to compact-coil conformational changes in PANI via formation of intra-molecular hydrogen bonds in presence of water in the solutions is proposed. Light scattering experiments support this conclusion. Addition of water to the protonated solution also caused expanded-coil to compact-coil conformational changes in protonated PANI. However, state of the polymer is dependent on the preparation history, i.e., which agent, acid or water, was added first to the solution.

EXPERIMENTAL DEVELOPMENT OF METHODS FOR THE PRODUCTION OF DURABLE CREASES AND CREASE-RESISTANCE IN WOOL FABRICS

Procedures and mechanisms concerned in the production of durable creases in wool fabrics are discussed. The experimental work, including testing methods, that has been carried out is described with special reference to treatments that are based on the application of a reagent capable of breaking disulphide bonds in presence of one that is effective in breaking hydrogen bonds. A significant increase in crease-resistance by the treated fabric is obtained by incorporating a relatively small concentration of a polyamide type of resin with the crease-retention preparation. A preliminary study of the dithio reduction is made on the model substance cystine. Technical aspects, mainly as consumer trials, are described.

Isomerization of some diene hydrocarbons in the presence of calcium amide

1. The relative rates of isomerlzation of 1,5-hexadiene, 2-methyl-1,5-hexadiene, and 2,5-dimethyl-1,5-hexadiene in presence of calcium amide are very close in value. 2. The results confirm the proposed mechanism of the displacement of double bonds in presence of metal amides.