Kinetic and thermodynamic parameters of hydrogen release during the heterogeneous catalytic dehydrogenation of <Emphasis Type="Italic">cis</Emphasis>- and <Emphasis Type="Italic">trans</Emphasis>-isomers of perhydro-m-terphenyl

Comparative studies on the temperature dependence of the dehydrogenation of cis- and trans-isomers of perhydro-m-terphenyl are performed in a flow catalytic reactor. Rate constants and equilibrium constants of all elementary acts of this reaction are calculated on basis of experimental data using the KINET 0.8 program for the mathematical modeling of the kinetics of complex reactions. The resulting data indicate that perhydro-m-terphenyl cis- and trans-isomers structural differences have no appreciable effect on dehydrogenation.     

Preparation of a Polymer via Condensation of <Emphasis Type="Italic">o</Emphasis>-Phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-Xylylene Dibromide and Its Properties

Condensation of para-dibromoxylene and ortho-phenylenediamine in glass ampule at 150°С in an alkaline aqueous solution has yielded polymer with completely substituted N–H hydrogen atoms, capable of formation of polymeric cation-radicals. Complexes of this polymer and N,N,N',N'-tetrabenzyl-o-phenylenediamine with Co(II), Ni(II), Cu(II), and Ag(I) have been obtained, and their structure has been studied.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.     

Comparison of catalytic performance of synthesized EU-1 zeolite with dealuminated EU-1 zeolite for <Emphasis Type="Italic">m</Emphasis>-xylene isomerization reaction

EU-1 zeolite was synthesized with high purity by a hydrothermal method and under optimum conditions: synthesis time 72 h, temperature 200°C, and aging time 12 h. Then, the synthesized EU-1 zeolite was modified by dealumination with nitric acid and the changes of the properties such as surface area, pore volume, and Si/Al ratio were investigated. The catalytic performance of these two catalysts was studied and compared with a commercial mordenite catalyst for meta-xylene isomerization reaction in a fixed bed reactor. The results showed that the modification of catalyst with acid increases Si/Al ratio from 25 to 50 due to the removal of a number of aluminium atoms from the framework of zeolite. Also the catalyst surface area increased from 300.237 m² g^?1 for EU-1 to 333.639 m² g^?1 for modified EU-1. According to results, the modified Eu-1 had higher para/ortho ratio, meta-xylene conversion, and para-xylene yield than EU-1 and commercial mordenite in the meta-xylene isomerization reaction.     

Photolysis of <Emphasis Type="Italic">ortho</Emphasis>-azidophenol in various solvents

The photolysis of ortho-azidophenol in water, ethanol, acetonitrile, chloroform, and benzene was studied by IR and electronic spectroscopy and thin-layer chromatography. It was found that an equilibrium between ortho-azidophenol and its quinonoid form occurred in benzene. In the photolysis of ortho-azidophenol in benzene, intramolecular hydrogen bonding facilitates the degradation of the azido group through the mechanism of formation of intermediate triazene structures. In the other solvents, which exclude intramolecular hydrogen bonding, the nitrene mechanism of photolysis yielding ortho-aminophenol, ortho-iminoquinone, and an azo compound is operative. The rate of formation of photolysis products depends on the nature of the solvent.     

Synthesis of <Emphasis Type="Italic">ortho</Emphasis>-carboranyl derivatives of (<Emphasis Type="Italic">S</Emphasis>)-asparagine and (<Emphasis Type="Italic">S</Emphasis>)-glutamine

(S)-Asparagine and (S)-glutamine ortho-carboranyl derivatives with free amino and carboxy groups in the α-position were synthesized. By an example of N ^γ-(1,2-dicarba-closo-dodecarboran-3-yl)-(S)-glutamine it was demonstrated that the developed synthetic approach carboranyl derivatives of amino acids allowed the preparation of optically pure isomers.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-Allyl- and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Diallyltrifluoromethanesulfonamides with Carboxylic Acid Amides under Oxidizing Conditions

Reactions of acetamide and benzamide with N-allyltrifluoromethanesulfonamide in the presence of t-BuOCl–NaI afforded exclusively 2,5-bis(chloromethyl)-1,4-bis(trifluoromethanesulfonyl)piperazine. Analogous reaction with N,N-diallyltrifluoromethanesulfonamide gave mixed halogenation product at only one C=C double bond of the substrate.     

Oxidation kinetics of Zn-5,15 bis(<Emphasis Type="Italic">ortho</Emphasis>-methoxyphenyl)-2,3,7,8,12,13,17,18-octamethylporphyrin with organic peroxides in <Emphasis Type="Italic">o</Emphasis>-xylene

With the purpose of further investigation of the effect of the steric strain of the porphyrin macroring in metal porphyrins on their redox properties, kinetics of oxidation of Zn-5,15 bis(ortho-methoxyphenyl)-2,3,7,8,12,13.17,18-octamethylporphyrin with organic peroxides in o-xylene at 295°C were studied spectrophotometrically to show that this process leads to complete destruction of the complex. Kinetic characteristics (k _ef, k _v) of the process were evaluated. The structure of the zinc porphyrin and its oxidation intermediates were obtained by quantum-chemical calculations. Steris strains in the metal prophyrin macroring were revealed and shown to enhance in the course of the reaction. An effect of the degree of deformational strain on the oxidation rate was noted.     

Kinetic investigation of the polymerization of <Emphasis Type="Italic">D</Emphasis>,<Emphasis Type="Italic">L</Emphasis>-lactide and glycolide via differential scanning calorimetry

The kinetics of polymerization of D,L-lactide and glycolide are studied via differential scanning calorimetry at different temperatures and concentrations of the catalyst tin octanoate. For the polymerization of D,L-lactide and glycolide, the enthalpies are determined to be ?17 ± 1.5 and 16.5 ± 1.5 kJ/mol, respectively. The time to attain reaction equilibration decreases from 300 to 100 min with an increase in temperature from 200 to 220°C. The time of reaction at 200°C decreases from 280 to 100 min as the concentration of the catalyst is increased from 500 to 830 ppm. When the polymerization of glycolide is conducted at temperatures below 200°C, the reaction is accompanied by crystallization of polyglycolide and an increase in the total enthalpy of the process.     

Kinetics and mechanism of benzyl <Emphasis Type="Italic">para</Emphasis>-chlorophenyl ketone oxidation

The oxidation of benzyl para-chlorophenyl ketone in chlorobenzene at 100°C occurs through the formation of short chains. Non-peroxide reaction products (1-(4-chlorophenyl)-2-hydroxy-2-phenyl-1-ethanone, para-chlorobenzyl, benzaldehyde, and para-chlorobenzoic acid) are formed not only by the transformation of hydroperoxide (1-(4-chlorophenyl)-2-hydroxy-2-phenyl-1-ethanone) but also (or solely) through the recombination of α-ketoperoxyl radicals with or without chain termination. α-Hydroperoxide decomposes predominantly through a heterolytic route to form para-chlorobenzoic acid and benzaldehyde. Benzaldehyde and 1-(4-chlorophenyl)-2-hydroxy-2-phenyl-1-ethanone undergo radical chain oxidation in the reaction medium to form benzoic acid (benzaldehyde), para-chlorobenzyl, and benzoic and para-chlorobenzoic acids (1-(4-chlorophenyl)-2-hydroxy-2-phenyl-1-ethanone). The homolytic decomposition of α-hydroperoxy ketone and α-hydroxy-α-hydroperoxy ketone causes the self-acceleration of the process and affords 1-(4-chlorophenyl)-2-hydroxy-2-phenyl-1-ethanone or, to a lesser extent, benzaldehyde and para-chlorobenzoic acid (α-hydroperoxy ketone). para-Chlorobenzoic acid substantially accelerates the heterolytic decomposition of α-hydroxy-α-hydroperoxy ketone and the oxidation of benzyl para-chlorophenyl ketone with peroxy acids to ester according to the Baeyer-Villiger mechanism. The rate constants of the main steps of the process and kinetic parameters are calculated by solving the inverse kinetic problem.     

Reversible hydrogenation—dehydrogenation reactions of <Emphasis Type="Italic">meta</Emphasis>-terphenyl on catalysts with various supports

For developing new composite systems (substrate—catalyst) for hydrogen storage, the activities of Pt and Pd catalysts on various supports were compared in reversible meta-terphenyl hydrogenation and perhydro-meta-terphenyl dehydrogenation. The microstructure of the catalysts was studied. Carbon-supported catalysts are more efficient in both reversible reactions than alumina-supported systems.     

Synthesis and structure of Pt(II) acetamidate complexes containing <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-substituted ethylenediamine and trimethylenediamine

Reactions of acetamide with platinum(II) diamines [Pt(N,N-DimeEn)Cl₂], [Pt(Tm)Cl₂], and [Pt(N,N-DimeTm)Cl₂] (N,N-DimeEn = (CH₃)₂N(CH₂)₂NH₂, Tm = NH₂(CH₂)₃NH₂, N,N-DimeTm = (CH₃)₂N(CH₂)₃NH₂) with preliminary precipitation of chlorine ions by silver salts gave binuclear Pt(II) acetamidates [Pt₂(CH₃)₂N(CH₂)₂NH₂)₂(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (I), [Pt₂(NH₂(CH₂)₃NH₂)₂)(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (II), and [Pt₂(CH₃)₂N(CH₂)₃NH₂)₂(μ-NHCOCH₃)₂](HSO₄)₂ (III), whose crystal structures were determined. Crystals of I are monoclinic: a = 14.459(2) Å, b = 17.197(3) Å, c = 9.822(2) Å, β = 105.923(10)°, V = 3348.6(8) ų, space group P2(1)/c, Z = 4, R _hkl = 0.0419 for 6663 reflections. Complex I is a binuclear acetamidate with bridging (NHCOCH₃)^? ligands, one of which is bound to two Pt atoms through the N and O atoms, and the other ligand is bound only through the N atom. The Pt-Pt distance is 2.987(1) Å. Crystals of II are monoclinic: a = 10.213(7) Å, b = 13.373(9) Å, c = 16.533(11) Å, β = 97.971(9)°, V = 2236(3) ų, space group P2(1)/n, Z = 4, R _hkl = 0.557 for 6462 reflections. The Pt-Pt distance is 3.057(1) Å. Crystals of III are monoclinic: a = 10.557(12) Å, b = 18.531(2) Å, c = 14.4744(17) Å, β = 108.705(2)°, V = 2682(5) ų, space group P2(1)/n, Z = 4, R _hkl = 0.569 for 8506 reflections. The Pt-Pt distance is 3.202(1) Å. Complexes II and III are binuclear acetamidates, in which two chelating Pt(Tm) or Pt(N,N-DimeTm) moieties are coordinated through the N and O atoms of (NHCOCH₃)^? cis-bridges.     

Electronic effect of substituents in coupling reactions between <Emphasis Type="Italic">para</Emphasis>-substituted benzamidoximes and nitrile ligands in <Emphasis Type="Italic">cis</Emphasis>-[PtCl<Subscript>2</Subscript>(EtCN)<Subscript>2</Subscript>] complex

The rate constants were determined for a number of reactions of nucleophilic addition of para-substituted benzamidoximes 4-RC₆H₄C(NH₂)=NOH to cis-[PtCl₂(EtCN)₂] at 23°C in acetone. A linear correlation between log (k _R/k _H) and σ _para was found, and reaction constant ρ²⁹⁶(σ _para ) was calculated. The prepared compounds were characterized by IR, ¹H NMR, and HR ESI⁺-MS.     

Gas-phase and supercritical <Emphasis Type="Italic">n</Emphasis>-pentane isomerization on H-mordenite

The skeletal isomerization of supercritical n-pentane on the H form of mordenite under flow conditions was studied for the first time. It was found that the conversion of supercritical n-pentane was 30–35% at 90% selectivity for isopentane at 260°C, 130 atm, and a liquid hourly space velocity of 30 h^?1. The catalyst was deactivated as the temperature was increased above 280°C. According to differential thermal analysis data, the deactivation was related to the deposition of condensation products on the surface. The resistance of the H form of the zeolite to poisoning in n-pentane isomerization in a gas phase at 1–8 atm was lower than that under supercritical conditions. It was found that H-mordenite deactivated under gas-phase reaction conditions at 260°C and 8 atm can be regenerated by passing to supercritical isomerization conditions (260°C and 130 atm).     

Control over <Emphasis Type="Italic">m</Emphasis>-nitrotoluene concentration in products of heterogeneous mononitration of toluene

Heterogeneous mononitration of toluene with sulfuric-nitric acid mixtures, occurring in the charged interfacial monolayer with high para selectivity, was studied. Ways to suppress the meta substitution in the toluene mononitration stage by controlling the nitrating mixture composition, process parameters, and catalytic additives were found.     

Neutron diffraction study of dehydrogenation of titanium carbohydrides TiC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>H<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>

The possibility of the synthesis of hydrogen-nonstoichiometric cubic titanium carbide ТiС _х of high purity from powdery nonstoichiometric cubic titanium carbohydride ТiС _х H _y or nonstoichiometric titanium carbide with admixture hydrogen by annealing in a continuously maintained vacuum of no worse than 1.33 × 10^–3 Pa at temperatures of 600–750°C for several hours has been shown. Similar annealing at higher temperatures (T ≥ 800°C) does not lead to the complete removal of hydrogen from a sample due to intensive sintering. In this case, it seems that pores between sintered particles are hydrogen traps, and the release of hydrogen through the surface of sintered particles is hindered.     

Photolysis of <Emphasis Type="Italic">meta</Emphasis>-azidophenol in solutions

The photolysis of meta-azidophenol in various organic solvents and aqueous solutions is studied by IR spectroscopy, electronic absorption spectroscopy, thin-layer chromatography (TLC), and analytical spot-test reactions. The polymeric derivatives of hydroxylamine are formed in organic solvents (benzene, chloroform, acetonitrile) via the interaction of nitrene with the phenol group of a neighboring m-azidophenol molecule. N-(meta-Hydroxyphenyl)hydroxylamine,—the product of the nitrene reaction with water, is formed in ethanol and aqueous solutions.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-acetyl- and <Emphasis Type="Italic">N</Emphasis>-ethoxycarbonyl-2-(1-cycloalken-1-yl)anilines with <Emphasis Type="Italic">meta</Emphasis>-cloroperbenzoic acid

Reaction of N-ethoxycarbonyl-2-(1-cycloalken-1-yl)anilines with meta-cloroperbenzoic acid leads to the corresponding 2-[1-o-(3-chlorobenzoyl)-2-hydroxycyclopent-1-yl]anilines. 5-(2-Acetylaminophenyl)-5-oxopentanic or 6-oxohexanic acids are formed as main products in the reaction of N-acetyl-2-(1-cycloalken-1-yl)anilines with m-chloroperbenzoic acid in CH₂Cl₂. N-Acetyl-2-(1-cyclopenten-1-yl)-3,6-dimethylaniline is an exception in this series since its reaction stops at the stage of epoxide formation.     

Phase transitions of the ZrNiH<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> hydride

The hydrogen pressure-ZrNiH _x hydride composition isotherms were determined under isoplethic experiment conditions during the desorption and sorption of hydrogen. According to the experimental data, the ZrNiH _x -H₂ system (0 < x < 2.229) experienced two phase transitions, hydrogenolysis with the absorption of large amounts of hydrogen and the reverse transition to the initial state. It was found that the β phase existed in the ZrNiH _x -H₂ system at least up to 410°C, and the region of its homogeneity was shifted toward the α solution. The homogeneity region of the γ phase at 250°C on the side depleted of hydrogen extended to the composition x = 1.50, and the temperature of its peritectoid decomposition was above 250°C. The hydrogenolysis reaction proceeded with the formation of the ?-ZrH_3.153?x -NiZr_0.7H_0.3x system, which had a much higher (higher by 200–300 torr) partial hydrogen pressure over the temperature range 0–240°C, that is, was unstable with respect to the initial system.     

Synthesis of amino acid conjugates of glycyrrhizic acid using <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-dicyclohexylcarbodiimide

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of N-hydroxyphthalimide, N,N'-dicyclohexylcarbodiimide, and tert-butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40–45% yield. The structure of the prepared compounds was confirmed by IR and ¹³C NMR spectroscopy.