Effect of Thiourea on the Kinetics of the Hydrogen Evolution Reaction at Iron and the Transport of Hydrogen through a Steel Membrane in Solutions of C<Subscript>2</Subscript>H<Subscript>4</Subscript>(OH)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O-HCl

The effect of thiourea (0.5–10 mM) on the kinetics of the hydrogen evolution reaction (HER) at iron and the hydrogen transport through a steel membrane out of ethylene glycol (containing 2 and 10 wt % H₂O) and aqueous solutions containing HCl (0.1–0.99 M) with a constant ionic strength equal to unity is studied in parallel experiments. The presence of 0.5 mM of thiourea in the solutions raises the overvoltage of hydrogen evolution, while a subsequent increase in its concentration does not effect the HER kinetics. The dependence of the flux of hydrogen diffusion through the membrane on the thiourea content passes through a maximum.     

New MnO–Nb(Ta)2O5 Phases Produced at High Pressures and Temperatures

Phase formation at high pressures and temperatures were studied in the MnO–Nb(Ta)₂O₅ system. New rhombohedral modifications of Mn₄Nb₂O₉ and Mn₄Ta₂O₉, two new modifications of MnTa₂O₆, and two modifications of Mn₂Ta₂O₇ were obtained. They were structurally identified.     

Reduction of plutonium to the bivalent state

Conclusions The existence of the bivalent state of plutonium and the standard oxidation potential of the Pu³⁺/Pu²⁺ couple, equal to –2.59 V, have been established for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 818–820, April, 1982.     

Synthesis of Functionally-substituted Pyrrolothiazolidines from Pyrrole-2-carbodithioates, CH-acids, and Haloacetylenes

Functionally substituted pyrrolothiazolidines have been synthesized by the sequential treatment of pyrrole-2-carbodithioates with methylene-reactive nitriles and haloacetylenes in a KOH-DMSO system.     

Chemical transformations of lignin during the biodegradation and organosolv pulping of deciduous wood

The lignins from the liquors in the organosolv pulping of aspen wood treated with wood-destroying fungi have been investigated using quantitative¹H and¹³C NMR spectroscopy and exclusion liquid chromatography. It has been shown that the biodegradation of lignin takes place in different ways according to the complex of enzymes produced by the fungi. Phanerochaete sanguinea causes degradation through predominant cleavage at alkyl-phenyl bonds, and Trametes villosus at the C-C bonds of the aliphatic chain. In addition to degradation reactions, polymerization (condensation) reactions also take place with the appearance of new C_ar-O-C and C_ar-C bonds. It has been established that the biological pretreatment of aspen wood ensuring partial degradation of the lignin leads to its more ready extraction in the process of organosolv pulping.Wood Chemistry Division of the Irkutsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 603–610, July–August, 1995. Original article submitted May 23, 1994.     

Conformations of methoxy(hydroxy)-substituted benzenes and benzaldehydes in the gas phase

The electronic structure ofo-methoxy(hydroxy)-substituted benzenes has been investigated by the combined use of photoelectron spectroscopy and molecular orbital calculations by means of the semi-empirical AM1 method. Absorption bands in the PE spectra have been assigned, the dependence of someπ-orbital energies on the molecular conformation has been found, and the estimation of the mean torsion angle of the OCH₃-group with the plane of the benzene ring has been carried out. The results obtained show that the gas-phase conformations of the heavy-atom framework of guaiacol and vanillin molecules are planar. For veratrole and veratraldehyde, nonplanar conformations with mean torsion angles ϕ ≈ 80° and 55°, respectively, have been observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1757–1760, October, 1993.     

Synthesis, crystal structure and inelastic neutron scattering in the infinite-layer compounds Sr1−xNdxCuO2

For the first time large samples of the nominal composition Sr_1−xNd_xCuO₂ (x=0.07, 0.15) 10 g in mass each have been prepared using a high-pressure technique. Neutron-diffraction and X-ray measurements have shown that the main phase in the samples obtained is of the infinite-layer structure which has been refined in the tetragonal P4/mmm space group. Both samples are not superconducting. Inelastic neutron scattering has been employed to search for crystalline-electric-field transitions in these compounds. The observed low-energy spectra exhibit one inelastic line of magnetic origin at 18 meV, comparable in energy with a crystalline-electric-field excitation in the high-T_c superconductor NdBa₂Cu₃O_x.     

Interrelation between Kinetics of the Hydrogen Ion Reduction on Iron and the Hydrogen Diffusion Flux into Carbon Steel in Acidic Solutions

Kinetic parameters of discharge of hydrogen ions, which depend on the nature of the slow stage in the Volmer–Tafel and Volmer–Heyrovský mechanisms, are obtained theoretically for commensurate rates of successive reactions on energetically-uniform and evenly-nonuniform surfaces. The results are compared with similar experimental parameters for the Armco iron in the system C₂H₄(OH)₂–H₂O + HCl. Upon adding 2–10 wt % H₂O into C₂H₄(OH)₂, the slow discharge stage gives way to the Tafel reaction if the hydrogen ion adsorption obeys the Temkin isotherm. Upon going to purely aqueous solutions, the discharge process becomes the limiting stage again. A change in the hydrogen diffusion flux through a steel membrane from these mixed solvents does not correlate with the nature of the stage that controls the cathodic reduction of hydrogen ions.     

Reaction of Alkylsulfanylchloroacetylenes with 1,1-Dimethylhydrazine

Alkylsulfanylchloroacetylenes react with 1,1-dimethylhydrazine in diethyl ether at 20–22°C to give, depending on the reactant ratio, 3,6-bis(alkylsulfanylmethyl)-1,1,4,4-tetramethyl-1,4-dihydro-1,2,4,5- tetrazine-1,4-diium dichlorides (yield 67–80%) or 1-[2-(alkylsulfanyl)-1-(2,2-dimethylhydrazono)ethyl]-1,1-dimethylhydrazinium chlorides. The latter readily undergo dequaternization to the corresponding 2-alkylsulfanyl-N ¹,N ²,N ⁴-trimethylethanohydrazide hydrazones (yield up to 53%).