Preparation of η5-C5H5COOH(CO)2Fe-η1-R carboxylic acids

η⁵-C₅H₄(COOH)(CO)₂FeR (R = Ph, C₅H₄Mn(CO)₃ or CH₂Ph) carboxylic acids were obtained in high yields via metallation with BuLi followed by treatment with CO₂.     

Solubility and solid phases in the systems zinc nitrate-dimethylcarbamide-water and cadmium nitrate-dimethylcarbamide-water at 25°C

Solubility isotherms have been studied in the systems Zn(NO₃)₂-(CH₃)₂NCONH₂-H₂O and Cd(NO₃)₂-(CH₃)₂NCONH₂-H₂O at 25°C. Crystallization fields have been determined for the congruent-melting compounds Zn(NO₃)₂ · 4(CH₃)₂NCONH₂ · 2H₂O (I) and Cd(NO₃)₂NCONH₂ (II). The compounds have been characterized by chemical analysis, differential thermal analysis, powder X-ray diffraction, and IR spectroscopy.     

Radical-cationic gaseous amino acids: a theoretical study

Three major forms of gaseous radical-cationic amino acids (RCAAs), keto (COOH), enolic (C(OH)OH), and zwitterionic (COO(-)), as well as their tautomers, are examined for aliphatic Ala(.+), Pro(.+), and Ser(.+), sulfur-containing Cys(.+), aromatic Trp(.+), Tyr(.+), and Phe(.+), and basic His(.+). The hybrid B3LYP exchange-correlation functional with various basis sets along with the highly correlated CCSD(T) method is used. For all RCAAs considered, the main stabilizing factor is spin delocalization; for His(.+), protonation of the basic side chain is equally important. Minor stabilizing factors are hydrogen bonding and 3e-2c interactions. An efficient spin delocalization along the N-C(alpha)-C(O-)O moiety occurs upon H-transfer from C(alpha) to the carboxylic group to yield the captodative enolic form, which is the lowest-energy isomer for Ala(.+), Pro(.+), Ser(.+), Cys(.+), Tyr(.+), and Phe(.+). This H-transfer occurs in a single step as a 1,3-shift through the sigma-system. For His(.+), the lowest-energy isomer is formed upon H-transfer from C(alpha) to the basic side chain, which results in a keto form, with spin delocalized along the N-C(alpha)-C=O fragment. Trp(.+) is the only RCAA that favors spin delocalization over an aromatic system given the low ionization energy of indole. The lowest-energy isomer of Trp(.+) is a keto form, with no H-transfer.     

Specific features of electrical properties of porous biocarbons prepared from beech wood and wood artificial fiberboards

This paper reports on comparative investigations of the structural and electrical properties of biomorphic carbons prepared from natural beech wood, as well as medium-density and high-density fiberboards, by means of carbonization at different temperatures T _carb in the range 650–1000°C. It has been demonstrated using X-ray diffraction analysis that biocarbons prepared from medium-density and high-density fiberboards at all temperatures T _carb contain a nanocrystalline graphite component, namely, three-dimensional crystallites 11–14 Å in size. An increase in the carbonization temperature T _carb to 1000°C leads to the appearance of a noticeable fraction of two-dimensional graphene particles with the same sizes. The temperature dependences of the electrical resistivity ρ of the biomorphic carbons have been measured and analyzed in the temperature range 1.8–300 K. For all types of carbons under investigation, an increase in the carbonization temperature T _carb from 600 to 900°C leads to a change in the electrical resistivity at T = 300 K by five or six orders of magnitude. The dependences ρ(T) for these materials are adequately described by the Mott law for the variable-range hopping conduction. It has been revealed that the temperature dependence of the electrical resistivity exhibits a hysteresis, which has been attributed to thermomechanical stresses in an inhomogeneous structure of the biocarbon prepared at a low carbonization temperature T _carb. The crossover to the conductivity characteristic of disordered metal systems is observed at T _carb ? 1000°C.     

General features and specifics of the kinetics of the pseudoliving radical polymerization of 4-vinylpyridine and styrene mediated by TEMPO

The kinetics of the pseudoliving radical polymerization of 4-vinylpyridine mediated by TEMPO is studied for the first time, and quantitative parameters characterizing the pseudoliving mechanism of the reaction, namely, the rate constant of reinitiation and the product of the equilibrium constant and the propagation-rate constant, are estimated. It is shown that the general kinetic features of the TEMPO-mediated polymerizations of 4-vinylpyridine and styrene (the pattern of kinetic curves and the zero reaction order with respect to the concentration of alkoxyamine) and the distinctive features of the polymerization of 4-vinylpyridine (an abnormally low rate and a high steady-state concentration of free TEMPO) are determined by three main factors: the rate of spontaneous initiation, the rate of self-termination of macroradicals, and the constant of equilibrium between active and dormant chains.     

Anode oxidation of copper in alkali media in the presence of glycine, α-alanine,and asparagine acid

The effect of glycine, α-alanine, and asparagine acid on the kinetics of anode processes occurring for copper in alkali electrolytes is studied. The experiments are performed in a background solution of 1 × 10⁻² M NaOH (pH 12). The concentrations of glycine and α-alanine are varied in the range of 1 × 10⁻⁶-1 × 10⁻¹ M, and the concentration of asparagine acid is varied in the range of 1 × 10⁻⁵-1 × 10⁻³ M. All amino acids used in this work have been found to stimulate anode oxidation of passivated copper, initiating local activation (LA) of the metal. Depending on the nature of amino acids, this effect occurs in various concentration ranges: for glycine and α-alanine, it takes place at c= 5 × 10⁻³-2 × 10⁻² M, while for asparagine acid, at c = 1 × 10⁻⁵−1 × 10⁻³ M. In addition to this general regularity, several individual peculiarities have been revealed: in the systems containing a monobasic amino acid additive, local activation occurs at E = 0.10–0.20 V, while in the presence of a dibasic amino acid, the local activation is observed at two potentials, E _LA¹ = 0.20–0.30 V and = E _LA² = 0.80–0.90 V, separated by the repassivation region.     

Structure formation of fullerene-containing propylene oxide oligomers in deuterium water

Structure formation of propylene oxide oligomers with terminal hydrophobic aliphatic fragment and of oligo(propylene oxides) additionally containing covalently bonded fullerene C₆₀ in deuterium water was studied by small-angle neutron scattering. Propylene oxide chains containing a long hydrophobic fragment undergo organization into spherical micelles, whereas the fullerene(C₆₀)-containing derivatives form rodlike structures (elongated “chains” of cross-linked micelles).     

Synthesis,structure, and properties of new spirooxindolodibenzodiazepine derivatives

An acid-catalyzed reaction of 3-(2-aminophenylamino)-5,5-dimethylcyclohexen-1-one with isatines leads to the formation of the earlier undescribed 3,3-dimethyl-2,3,4,5,10,11-hexahydrospiro[1H-dibenzo[b,e][1,4]diazepine-11,3′-2H-indole]-1,2′-dione derivatives (6). Spiranes 6 upon heating undergo auto-redox rearrangement with disintegration to 3,3-dimethyl-1,2,3,4-tetrahydrophenazine and the corresponding oxindole. Crystals of four derivatives of compound 6 were studied by X-ray diffraction method.     

Kinetics and mechanism of oxidation with peroxides of ferrocenylacetic acid and methyl ferrocenylacetate

The reaction of ferrocenylacetic acid and its methyl ester with peroxides ROOR (R = H, t-Bu) in organic solvents was studied. It is shown that direct involvement of the substituent in this process leads to abnormally high reactivity of the acid toward H₂O₂ and t-BuOOH as compared with both the ester and ferrocene in a model system of Cp₂Fe + PhCOOH. An unusual shift of the absorption maximum of the ferrocenyl cation formed in the reaction course to longer wavelengths reaching up to several tens of nanometers was discovered.     

Effect of carbonization temperature on the microplasticity of wood-derived biocarbon

The uniaxial compression strength under stepped loading and the 325-nm-stepped deformation rate of biocarbon samples obtained by carbonization of beech wood at different temperatures in the 600–1600°C range have been measured using high-precision interferometry. It has been shown that the strength depends on the content of nanocrystalline phase in biocarbon. The magnitude of deformation jumps at micro- and nanometer levels and their variation with a change in the structure of the material and loading time have been determined. For micro- and nanometer-scale jumps, standard deviations of the differences between the experimentally measured deformation rate at loading steps and its magnitude at the smoothed fitting curve have been calculated, and the correlation of the error with the deformation prior to destruction has been shown. The results obtained have been compared with the previously published data on measurements of the elastic properties and internal friction of these materials.