Search results for "Bonding"
showing 10 items of 996 documents
ChemInform Abstract: Reactions of Benzothiete with Phosphorus Nucleophiles. A Novel Type of Arbuzov Rearrangement.
1989
The reaction of trialkylphosphites or related P-nucleophiles with benzothiete (1) leads to zwitter ionic species, which show an Arbuzov - like rearrangement to the products 4 and 7, respectively. New heterocyclic ring systems are generated in the case of cyclic esters. The normal SN2 reaction leads to the 1:2 adducts 9, whereas in an SN1 process the 1:1 adduct 13 is formed.
Capping Parallel β-Sheets of Acetyl(Ala)6NH2 with an Acetyl(Ala)5ProNH2 Can Arrest the Growth of the Sheet, Suggesting a Potential for Curtailing Amy…
2014
We present ONIOM calculations using B3LYP/d95(d,p) as the high level and AM1 as the medium level on parallel β-sheets containing four strands of Ac-AAAAAA-NH2 capped with either Ac-AAPAAA-NH2 or Ac-AAAPAA-NH2. Because Pro can form H-bonds from only one side of the peptide linkage (that containing the C═O H-bond acceptor), only one of the two Pro-containing strands can favorably add to the sheet on each side. Surprisingly, when the sheet is capped with AAPAAA-NH2 at one edge, the interaction between the cap and sheet is slightly more stabilizing than that of another all Ala strand. Breaking down the interaction enthalpies into H-bonding and distortion energies shows the favorable interaction…
Hydrophobicity of ionisable compounds studied by countercurrent chromatography
2011
Countercurrent chromatography (CCC) is a liquid chromatography technique in which the stationary phase is also a liquid. The main chemical process involved in solute separation is partitioning between the two immiscible liquid phases: the mobile phase and the support-free liquid stationary phase. The octanol-water partition coefficients (P(o/w)) is the accepted parameter measuring the hydrophobicity of molecules. It is considered to estimate active principle partitioning over a biomembrane. It was related to the substance biological activity. CCC is able to work with an octanol stationary phase and an aqueous mobile phase. In this configuration, CCC is a useful and easy alternative to measu…
N,N-Di-n-octyl-N,N-dimethyl and N,N-di-n-nonyl-N,N-dimethyl ammonium cholates: 13C and 15N CPMAS NMR, powder X-ray diffraction and thermoanalytical c…
2009
Abstract N,N-Di-n-octyl-N,N-dimethyl cholate (1) and N,N-di-n-nonyl-N,N-dimethyl ammonium cholate (2) have been prepared by crystallization from equimolar mixtures of sodium cholate and quaternary N,N-di-n-alkyl-N,N-dimethyl (n-octyl or n-nonyl) ammonium bromides. The formed crystalline materials have been structurally characterized by 13C and 15N cross polarization magic angle spinning (CPMAS) NMR, powder X-ray diffraction (PXRD) and thermoanalytical (TGA/DTA and DSC) methods and compared with each other. Powder X-ray diffraction patterns of 1 and 2 reveal clear similarities. Combined with the thermoanalytical data of these structures an existence of two hydrated polymorphs (most probably …
A study of the influence of ionic liquids properties on the Kemp elimination reaction
2009
The morpholino-induced elimination of 5-nitrobenzisoxazole into the relevant 2-cyano-4-nitrophenolate has been used as a sample reaction in order to investigate molecular properties of some room temperature ionic liquids. The kinetic study was carried out at 298 K by means of spectrophotometric measurements. Ionic liquids, which differ in both their cation and anion properties, were used as solvent systems. In particular, aliphatic (pyrrolidinium, piperidinium, and ammonium) and aromatic (imidazolium and pyridinium) ionic liquids were used. For aromatic cations, imidazolium ions having different hydrogen-bond donor ability or a different alkyl-chain length were taken into account. The anion…
Metal Telluride Clusters Composed of Niobocene Carbonyl, Telluride, and Cobalt Carbonyl Units: Syntheses, Structures, and Reactivity
2000
Abstract: The reaction of [Cp#2NbTe2H] (1#; Cp# = Cp* (C5Me5) or Cp(x) (C5Me4Et)) with two equivalents of [Co2(CO)8] gives a series of cobalt carbonyl telluride clusters that contain different types of niobocene carbonyl fragments. At 0 degrees C, [Cp#2NbTe2CO3(CO)7] (2#) and [Co4Te2(CO)10] (3) are formed which disappear at higher temperatures: in boiling toluene a mixture of [cat2][Co9Te6(CO)8] (5#) (cat= [Cp#2Nb(CO)2]+) and [cat2][Co11Te7(CO)10] (6#) is formed along with [cat][Co(CO)4] (4#). Complexes 6# transform into [cat][Co11Te7(CO)10] (7#) upon interaction with HPF6 or wet SiO2. The molecular structures of 2(Cp(x)), 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) have been determined by X-ray cr…
A DFT study of the ionic [2+2] cycloaddition reactions of keteniminium cations with terminal acetylenes
2015
Abstract The molecular mechanism of the ionic [2+2] cycloaddition (I-22CA) reactions of a keteniminium cation (KC) with acetylene and propyne has been investigated using DFT methods at the MPWB1K/6-311G(d,p) level. These I-22CA reactions take place via a two-step mechanism. The first step is the nucleophilic attack of these alkynes on the central carbon of KC, yielding cyclopropene intermediates, while the second step corresponds to the conversion of these intermediates into more stable cyclobuteniminium cations (CCs). The first step is the rate-determining step, while the second step is responsible for the formation of the two regioisomeric CCs experimentally observed in the reaction with …
Crystal structure of a novel bismuth phthalocyanine-bismuth iodide complex
1999
Abstract A new phthalocyaninato complex of bismuth with formula [(BiPc) 4 (Bi 4 I 16 )] was obtained in the reaction of bismuth with 1,2-dicyanobenzene in iodine vapour. The crystal and molecular structure of the complex was determined by single crystal X-ray diffraction. The unit cell consists of four discrete (BiPc) + cations and (Bi 4 I 16 ) 4− anions. The (Bi 4 I 16 ) 4− complex anion is formed by four edge-sharing BiI 6 octahedra. The arrangement of molecules in the crystalline structure of the complex is mainly determined by ionic attraction between the (BiPc) + and (Bi 4 I 16 ) 4− moieties, i.e. each (Bi 4 I 16 ) 4− complex anion is encapsulated between four (BiPc) + cations. The str…
Host–guest blue light-emitting electrochemical cells
2014
Carbazole, a commonly used hole-transporter for organic electronics, has been modified with an imidazolium cation and a hexafluorophosphate counter-anion to give an ionic hole-transporter. It has been applied as one of the hosts in a host–guest blue light-emitting electrochemical cell (LEC) with the neutral blue emitter FIrPic. We have obtained efficient and bright blue LECs with an electroluminescence maximum at 474 nm and efficacy of 5 cd A−1 at a luminance of 420 cd m−2, thereby demonstrating the potential of the ionic organic charge-transporters and of the host–guest architecture for LECs.
The logic of the gift and the bonding value: a new perspective for business management
2011
PurposeThis paper aims to conceptualize business relationships so as to include in these dimensions of both gift and gratuity, to develop the concept of “bonding value”, and to offer some ideas for the use of this within firms.Design/methodology/approachThe paper analyses the concept of “bonding value”, distinguishing it from the concepts of “exchange value” and “use value” that are normally used in business, and attempts to investigate its practical implications.FindingsThe paper shows how evaluating both the relationships within the organization and between firm and stakeholders in terms of “bonding value” can have effects on the economic, organizational and social aspects of a firm's act…