Thermodynamic properties of triphenylantimony dibenzoate

The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph₃Sb(OC(O)Ph)₂ is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph₃Sb(OC(O)Ph)₂ is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph₃Sb(OC(O)Ph)₂ in the crystalline and liquid states are calculated from the obtained experimental data: C_p^°(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.     

PtIr/C Catalysts Synthesized by Electrochemical Dispersion Method for Proton Exchange Membrane Fuel Cells

PtIr/C electrocatalyst with the metal phase uniformly distributed over the carbon support surface and the average size of PtIr nanoparticles of 5.9 nm is synthesized by electrochemical dispersion of Pt₉₀Ir₁₀ alloy under the action of alternating pulse current. It is shown that the presence of iridium within the composition of a Pt/C catalyst lowers down the overpotential of CO oxidation and increases catalyst’s specific activity with respect to electrochemical oxidation of ethanol.     

Thermodynamic Properties of Styrenetricarbonylchromium, α-Methylstyrenetricarbonylchromium,and p-Methylstyrenetricarbonylchromium in the Range 0-450 K

The thermodynamic properties of styrenetricarbonylchromium, -methylstyrenetricarbonylchromium, and p-methylstyrenetricarbonylchromium were studied with adiabatic vacuum and dynamic calorimeters. The heat capacity in the range 5-450 K (error about 0.3% in most cases) and the temperatures and enthalpies of the phase transitions were determined. The experimental data were used to calculate the thermodynamic functions C ⁰ _p(T), H ⁰(T) - H ⁰(0), S ⁰(T), and G ⁰(T) - H ⁰(0) for the range from 0 to 330-400 K, and also the isochoric heat capacity C _v and its lattice (_Cv,latt) and atomic (C _v,at) contributions for the range from 0 K to T ⁰ _m; the parameters = C ⁰ _p/C _v were evaluated. The thermodynamic properties were considered in relation to the composition and structure of the compounds.     

A study of the dioxane lignin of the stems of the cotton plant of variety S-4880

The dioxane lignin (DLA) has been isolated from the ripe stems of a cotton plant of the variety S-4880 B by a modification of Pepper's method. The yield was 16.9% on the Komarov lignin. The semiempirical formula of a phenylpropane structural unit has been calculated on the basis of elementary and functional analyses. It has been established that the amount of the main functional groups in the DLA and in the lignins isolated from the varieties of 108-F and Tashkent-2 basically coincide, but the DLA investigated was appreciably more highly methoxylated. The IR, UV, and PMR spectra of the DLA have been taken. The molecular-weight distribution of the DLA has been investigated and it has been shown that is is poly-disperse and has a weight-average molecular weight of 7400. Nitrobenzene oxidation and cleavage with sodium and liquid ammonia of the isolated DLA has shown that guaiacyl structural units predominate in it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 430–434, May–June, 1987.     

Calorimetric study of thermodynamics of production of polybutene-1, polypentene-1, 4-methylpentene-1 and properties of reagents between 0 and 670 K

The heat capacitiesC ₀ ^p of polybutene-1, polypentene-1, poly-4-methylpentene-1 and 4-methylphentene-1 were studied calorimetrically from 6 to (500–700) K. Temperatures, enthalpies of melting of various crystalline forms and the parameters of the glass transition were determined. The thermodynamic functionsH ⁰(T)?H⁰(0), S⁰(T) andG ⁰(T)?H⁰ (0) were calculated between 0 K and (500–700) K. From the calorimetric values obtained and literature data, the thermodynamic characteristics of the following processes were estimated for the corresponding alkenes-1, andcis-andtrans-alkenes-2: the polymerization of alkenes-1, the monomer-isomerization polymerization ofcis- andtrans-alkenes-2 to polyaklenes-1 and the isomerization ofcis- andtrans-aklenes-2 to alkenes-1 in the same temperature interval at standard pressure.     

Titanium(4+) and zirconium(4+) dichloride complexes with pyridinedicarboxylic acid derivatives as ethylene polymerization catalysts

Titanium(4+) and zirconium(4+) complexes with pyridinedicarboxylic acid derivatives have been synthesized. The composition and structure of the synthesized 2,6-bis(diphenylhydroxymethyl)pyridine complexes have been corroborated by NMR and IR spectroscopy, and elemental analysis. The complexes activated with methylaluminoxane (MAO) are catalytically active in ethylene polymerization, Depending on the Ti/Al_MAO ratio, the catalytic activity of the complexes varies between 90 and 420 kg PE/mol Ti h atm.     

Electrochemical Hydrogenation of α-Arylvinylphosphonic Acids on Platinum and Palladium Modified with Adatoms

A general characteristic of cathodic reduction of -phenylvinylphosphonic acid and its methyl- and chloro-parasubstituted derivatives on Pt/Pt, Pd/Pt, and Pd/Pt modified with Cd and Cu adatoms, is given. At effective pressures of about 10³–10⁴ Pa the processes occur at high rates and at some potentials are limited by the reactant diffusion from the bulk solution. In the presence of Cd and Cu adatoms two reduction waves (presumably, single-electron) may be isolated, i.e. the hampering by adatoms is more pronounced for a second successive stage of the process. At low effective hydrogen pressures the hydrogenation rate is higher on Pd electrodes, which possess a larger sorption capacity. Potential intervals where the reduction of substituted reactants may be complicated by destruction, are found. It is shown that -phenylvinylphosphonic acid undergoes a complete reduction with a current efficiency of 100% in both hydrochloric- and sulfuric-acid solutions. Conditions where the reduction of -(4-chlorophenyl)vinylphosphonic acid proceeds largely without destruction are found. Prospects for use of electrochemical reduction as a preparative method of a selective production of -arylethylphosphonic acids are considered.