Unusual behavior of methylidentriphenylphosphorane in reactions with seven-membered lactols

Methylidenetriphenylphosphorane in reactions with seven-membered lactols and their aluminates can act as a reducer converting them into the corresponding diols.     

Factors determining the catalytic activity of the mixed micellar system cetyltrimethylammonium bromide-Brij-35 in the hydrolysis of a phosphonic acid ester

The micellization and surface properties, Stern layer micropolarity, and catalytic action of the cetyltrimethylammonium bromide-Brij-35 system in the alkaline hydrolysis of O-ethyl O-p-nitrophenyl chloromethylphosphonate have been investigated at different proportions of the constituent surfactants. This system has unique, invertible catalytic properties ranging from acceleration of the hydrolysis reaction by more than one order of magnitude to strong inhibition of this reaction and even termination of the reaction at certain proportions of the surfactants. The factors in the changes of the catalytic effect under variation of the surfactant ratio are micropolarity in the reaction zone and surface potential. A likely cause of the termination of the process is the shift of the reaction zone from the surface layer to the micelle core, where the environment is less polar.     

New organized systems based on amphiphilic oxyethylated calix[4]arene

The aggregation of amphiphilic oxyethylated calix[4]arene is studied in the absence and presence of polyethyleneimine. At low calixarene concentrations, large ensembles with a hydrodynamic diameter of about 100 nm are formed and coexist with small (smaller than 10 nm) aggregates, which are observed in the entire concentration range. It is established that calixarene-based systems catalyze the neutral hydrolysis of bis(chloromethyl)phosphinic acid p-nitrophenyl ester, with the catalytic effect being as high as two orders of magnitude in the presence of La(III) ions. The rate of hydrolysis of phosphonates depends on the composition of the supramolecular system. The maximum acceleration exceeds three orders of magnitude in comparison with alkaline hydrolysis of the substrates.     

Concentration phase transition near the stoichiometric composition of vanadium monoxide VO<Subscript>1.00</Subscript>

The concentration dependences of the magnetic susceptibility and lattice parameter of cubic vanadium monoxide have been measured in the composition range from VO_0.81 to VO_1.07. Near the stoichiometric composition VO_1.00, the concentration dependences exhibit a stepwise increase in the specific magnetic susceptibility (by approximately 0.7 × 10^?6 cm³/g) and lattice constant (by about 0.002 nm). These effects can be related to the concentration phase transition, which occurs in vanadium monoxide with a change from a substoichiometric composition to superstoichiometric. At such a transition, along with a decrease in the concentration of oxygen vacancies, tetrahedrally coordinated vanadium interstitials are formed, as a result of which the B1 structure changes to a more complex cubic phase structure with the same space group Fm-3m.     

Solvent effect on the rate of ester interchange of p-nitrophenyldiethylphosphate

The reaction of p-nitrophenyldiethylphosphate with sodium phenolate takes place readily in aprotic polar solvents. Bimolecular rate constants of this reaction increase with increased concentration of the phenolate in such solvents as dimethylsulfoxide (DMSO), dimethylformamide (DMF), or hexamethylphosphoric amide (HMPA), but decrease in acetonitrile or acetone; this is caused by the association of sodium phenolate, and the different reactivities of free ions and ion pairs. The addition of 18-crown-6 to the reaction mixture decreases the reaction rate, because of the reduced reactivity of the complex formed by the crown ether with the phenolate ion pair.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1968–1972, September, 1991.     

The influence of imperfection of the crystal lattice on the electrokinetic and magnetic properties of disordered titanium monoxide

The conductivity and magnetic susceptibility of disordered titanium monoxide TiO_y (0.920≤y≤1.262) containing vacancies in titanium and oxygen sublattices are investigated. For TiO_y monoxides with an oxygen content y≤1.069, the temperature dependences of the conductivity are described by the Bloch-Grüneisen function at a Debye temperature ranging from 400 to 480 K and the temperature dependences of the magnetic susceptibility are characterized by the contribution from the Pauli paramagnetism due to conduction electrons. The behavior of the conductivity and magnetic susceptibility of TiO_y monoxides with an oxygen content y≥1.087 is characteristic of narrow-gap semiconductors with nondegenerate charge carriers governed by the Boltzmann statistics. The band gap ΔE between the valence and conduction bands of TiO_y monoxides with y≥1.087 falls in the range 0.06–0.17 eV.     

Complexes of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide with transition metal nitrates. Micelle-forming,solubilizing, and adsorption properties

Amphiphilic complexes of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide (D-16) with nitrates of transition metals (La³⁺, Cu²⁺, Ni²⁺, and Co²⁺) have been synthesized and characterized. Absorption spectrophotometry in the UV, visible, and IR regions, as well as ¹Н NMR spectroscopy, have been employed to study their spectral properties in water and organic media. Adsorption properties and micelleforming and solubilizing abilities of the amphiphilic complexes have been investigated in aqueous solutions by the methods of tensiometry and conductometry, as well as by solubilization of a water-insoluble dye (Orange OT). The values of the critical micelle concentration, adsorption parameters at a water/air interface, and solubilization capacity S of complex micelles have been determined. It has been shown that the most pronounced decrease in the critical micelle concentration (as large as two to three times) and differences in the adsorption characteristics and the S values as compared with those of ligand D-16 are observed for complexes of copper and lanthanum. The S values for these complexes are 1.3?2.5 and 3?6.5 times higher than those for D-16 and cetyltrimethylammonium bromide, respectively.     

Structure and supramolecular organization of tri-n-butyl(octadecyl)phosphonium tetrafluoroborate and its influence on catalytic activity of stabilized palladium nanoparticles

Russian Chemical Bulletin - A crystal structure and aggregation properties of tri-n-butyl(octadecyl)phosphonium tetrafluoroborate were studied. Palladium nanoparticles stabilized by this...