Search results for "SOLVENT"
showing 10 items of 1395 documents
“Water-stable boron-iodinated dicarbollide dianions [7,8-nido-C2H2B9I9]2−and [7,8-nido-C2H2B9I8H]2−”
2007
The reaction of 3,4,5,7,8,9,10,11,12-I(9)-1,2-closo-C(2)B(10)H(3) with KOH/EtOH gave a mixture of the boron periodinated [1,2,3,4,5,6,9,10,11-I(9)-7,8-nido-C(2)B(9)H(2)](2-) and the highly iodinated on boron [1,2,4,5,6,9,10,11-I(8)-7,8-nido-C(2)B(9)H(3)](2-) in approximately 50% each. Moreover, 3,4,5,6,7,8,9,10,11,12-I(10)-1,2-closo-C(2)B(10)H(2) was reacted with KOH/EtOH to purely produce [1,2,3,4,5,6,9,10,11-I(9)-7,8-nido-C(2)B(9)H(2)](2-). It is the first dinegative dicarbollide stable in water or protic solvent reported in literature.
Influence of structural factors and enzyme type on the reactivity and enantioselectivity of the enzymatic esterification of bicyclic meso dialcohols
1992
The meso dialcohols 1–7, obtained from the Diels-Alder adducts furan/maleic anhydride, furan/dimethyl acetylenedi-carboxylate, and cyclopentadiene/maleic anhydride, were subjected to enzymatic esterification in organic solvents. A mixture of the corresponding chiral monoacetates and the meso diacetates was obtained. It has been found that reaction rate and enantioselectivity markedly depend on substrate structure, temperature, enzyme type, and nature of the solvent. The presence of an oxygen bridge and an exo configuration are the two structural features which lead to the highest enantioselectivity values.
Supramolecular hydrogen-bonding tautomeric sulfonamido-phosphinamides: a perfect P-chirogenic memory
2011
P-chirogenic, supramolecular hydrogen-bonding C1-symmetrical sulfonamido–phosphinamides (METAMORPhos) have been successfully prepared. They were all found to possess a characteristic prototropic equilibrium between the PIII and the PV tautomers that is slow on the NMR spectroscopic timescale. Despite the dynamic and reversible protonation of the P centre, the P-chirogenic information was found to be retained in the tautomerization process, even in a protic solvent environment. Several strategies to access the corresponding enantiopure compounds were investigated, such as diastereoselective crystallization, or enantioselective synthesis. It was possible to resolve such a class of chiral liga…
Conductance in homomorphous solvents: Tetrabutylammonium salts and alkali picrates in butyrolactone-sulfolane mixtures
1983
Conductance measurements are reported for LiPi, NaPi, KPi, RbPi, CsPi, Bu4NPi, Bu4NBr, Bu4NClO4, Bu4NNO3, and Bu4NBBu4 at 25°C in γ-butyrolactone-sulfolane mixtures. In these mixtures of solvents that are practically homomorphous, isodielectic and with comparable dipole moments, the ion pair association and ionic mobilities of large ions conform to the expectations of the primitive model. Electrolytes containing lithium or sodium ions show anomalies indicating that other factors besides shape, dipole moment, and polarizability of the solvent molecules are involved in the association and transport processes of these ions.
Sulphides of the platinum group elements—12. Bis(tetraphenylphosphonium) pentakaidekakissulphido platinates(IV)
1991
Abstract Synthetic routes to tetraphenylphosphonium salts of [PtSx]2− are outlined, where x = 15 or 18. Generally, (PPh4)2[Pt(S5)3] is formed most readily. The compound [(C6H5)4P]2[PtS15], always solvated, has been obtained by synthesis in acetonitrile (sulphur, triethylamine, H2S and [PPh4]2[PtCl6]) and by metathesis (in DMF) from the known hydrated ammonium compound (NH4)2[Pt(S5)3]2H2O+2[Ph4P]Br→(Ph4P)2[Pt(S5)3]· DMF+2NH4Br, and from the dismutation (in acetone) 3PtS172−→PtS152−+2PtS182−. X-ray diffraction shows that crystals obtained from DMF and acetone are the solvated salts [Ph4P]2· [Pt(S5)3]· S, with solvent molecules (S) uncoordinated. In both, the three platinopentathian rings rela…
Study of AOT-stabilized microemulsions of urea dispersed in carbon tetrachloride
2003
Measurements of some physico-chemical properties (density, viscosity, permittivity) of the urea/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/CCl4 system as a function of the volume fraction of the dispersed phase (0<Φ<0.7) at various urea to AOT molar ratio (Rurea) have been carried out at 25 °C. The experimental data analysis are consistent with the hypothesis that urea is entrapped as small-size molecular clusters within the hydrophilic core of the AOT reversed micelles and that this structure is preserved well above a threshold Φ value where a percolative transition occurs. Besides, X-ray diffraction spectra of samples at Φ=1, obtained by complete evaporation under vacuum of the apolar …
Hierarchical Ordering in Ternary Co-Crystals of C60, N-Benzyl Ammonium Resorcinarene Bromide and Solvent Molecules
2014
Co-crystallization of C60 together with an N-benzyl ammonium resorcinarene bromide from toluene:1,2-dichloroethane mixture results in ternary co-crystals where the modulated C60 lattice entraps dimeric resorcinarene assemblies, which, in turn, have 149 and 280 A3 cavities filled with 1,2-dichloroethane molecules.
Ionic and Free Solvent Motion in Poly(azure A) Studied by ac-Electrogravimetry
2011
International audience; This work is focused on the mechanistic aspects of the redox behavior of poly(azure A) taking advantage of the controlled modulation of their oxidation states by ac-electrogravimetry. The originality of this technique is its ability to discriminate between cation and anion involved in the charge compensation process and the accompanying free solvent transfer, directly or indirectly. Two processes were proposed where the faster ionic exchange is considered to be the participation of the anion species acting as counterions whereas the slower one is related to the proton transfer. The proton is implied as reactants for the two electroactive sites identified in the polym…
Tetraurea calix[4]arenes with sulfur functions: synthesis, dimerization to capsules, and self-assembly on gold.
2007
Various calix[4]arene derivatives, fixed in the cone conformation by decylether groups and functionalized at their wide rim by urea residues, were synthesized. In two compounds (4f,g) sulfur functions were attached to the urea groups via different spacers in order to allow binding to metal surfaces. While they exist as single molecules in polar solvents, tetraurea calix[4]arenes of this type (4) combine to form dimeric capsules in aprotic, apolar solvents. A solvent molecule is usually included in such a capsule, if no guest with a higher affinity is present. In the presence of an equimolar amount of the tetratosylurea 5, the exclusive formation of heterodimers, consisting of one molecule o…
Solvent-dependent formation of Os(0) complexes by electrochemical reduction of [Os(CO)(2,2'-bipyridine)(L)Cl2]; L = Cl(-), PrCN.
2014
Cyclic voltammetry and ultraviolet-visible/infrared (UV-vis/IR) spectroelectrochemistry were used to study the cathodic electrochemical behavior of the osmium complexes mer-[Os(III)(CO) (bpy)Cl3] (bpy = 2,2'-bipyridine) and trans(Cl)-[Os(II)(CO) (PrCN)(bpy)Cl2] at variable temperature in different solvents (tetrahydrofuran (THF), butyronitrile (PrCN), acetonitrile (MeCN)) and electrolytes (Bu4NPF6, Bu4NCl). The precursors can be reduced to mer-[Os(II)(CO) (bpy(•-))Cl3](2-) and trans(Cl)-[Os(II)(CO)(PrCN) (bpy(•-))Cl2](-), respectively, which react rapidly at room temperature, losing the chloride ligands and forming Os(0) species. mer-[Os(III)(CO) (bpy)Cl3] is reduced in THF to give ultimate…