Showing papers in "Russian Chemical Bulletin in 1993"
54 citations
TL;DR: The history of the discovery of carbyne, the chemical and physical methods used to obtain it, the analysis of its structure, and some of its properties are briefly considered in this article.
Abstract: The history of the discovery of carbyne, the chemical and physical methods used to obtain it, the analysis of its structure, and some of its properties are briefly considered. The prospects for its practical applications are discussed
50 citations
TL;DR: In this paper, it was assumed that the interaction of H2O2 with VO3− gives rise to generation of HO radicals and other radical-like vanadium containing species that abstract a hydrogen atom from an alkane, RH.
Abstract: Alkanes (cyclohexane, hexane, heptane isomers) are effectively oxidized in CH3CN at 20–70°C by hydrogen peroxide when catalyzed by a Bu4NVO3-pyrazine-2-carboxylic acid system. Alkyl hydroperoxide is the main product; an alcohol and a ketone or an aldehyde are also formed. Under these conditions benzene is oxidized to give phenol, while alkyl benzenes yield oxygenation products both of the ring and the side chain. It has been assumed that the interaction of H2O2 with VO3− gives rise to generation of HO radicals and other radical-like vanadium containing species that abstract a hydrogen atom from an alkane, RH. The radical R. formed reacts with O2 to produce ROO. which is then transformed to alkyl hydroperoxide.
44 citations
TL;DR: The self-organization of the trans-isomers of the styryl dyes upon complexation with the Mg2+ cations into dimers with a fixed mutual arrangement of multiple bonds was studied in this article.
Abstract: Styryl dyes containing a crown ether group and a heteroaromatic moiety with a sulfoalkylN-substituent (1a,b) undergo photocyclodimerization in acetonitrile in the presence of Mg(ClO4)2 to give only the typeA isomer of cyclobutane derivative (2a,b). The photochemical regio- and stereoselectivity of the cycloaddition is explained by self-organization of thetrans-isomers of the styryl dyes upon complexation with the Mg2+ cations into dimers with a fixed mutual arrangement of multiple bonds.
23 citations
TL;DR: A number of cyanoacetates have been synthesized: Cyanoacetoxymethyitrimethylsilane (Cyanoaceto-methyl-silane) as discussed by the authors.
Abstract: A number of cyanoacetates have been synthesized: cyanoacetoxymethyitrimethylsilane (1), cyanoacetoxymethylpentamethyldisiloxane (2), cyanoacetoxyetoxymethylpentamethyldisiloxane (3). They were converted by the Knoevenagel reaction to novel esters of a-cyanoacrylic acid (4–13) containing silicon atoms in the ester groups and having the general formula RCH=C(CN)COOCH2X (where R=H, 4-MeOC6H4, MeCH=CH, 2-furyl; X=SiMe3, SiMe2OSiMe3, CH2OCH2SiMe2OSiMe3). These compounds are capable of copolymerization with esters of cyanoacrylic acid which are the precursors to adhesives for cold curing.
22 citations
TL;DR: In this paper, a new cluster-type monomer [Fe3O(OCOCH=CH2)6]OH · 3H2O was synthesized by the reaction of acrylic acid with freshly prepared iron hydroxide.
Abstract: A new cluster-type monomer [Fe3O(OCOCH=CH2)6]OH · 3H2O was synthesized by the reaction of acrylic acid with freshly prepared iron hydroxide. The monomer was characterized by various physicochemical methods. It has been shown that the acid residues are bound to the metal atoms through carboxyl groups in a bridge-like or bidentate fashion, and the double bond does not participate in the coordination. The mechanism of thermal fragmentation of the [Fe3O(OCOCH=CH2)6]+ cluster was studied. It was demonstrated that the radical polymerization of this monomer involved bidentate acrylate groups. No reduction of Fe3+ during the polymerization was observed.
21 citations
TL;DR: In this paper, the authors investigated the thermal decomposition of melted hydroxylammonium nitrate and found that the initial rate is proportional to the square of the concentration of HNO3 formed due to dissociation of the salt, and the activation energy of this process is 15.3±1.8 kcal/mol.
Abstract: The kinetics of thermal decomposition of melted hydroxylammonium nitrate have been investigated by the rate of heat production in the temperature range 84.8–120.9°C. The decomposition proceeds with autocatalysis and up to 60 % of conversion the rate of the process increases proportionally to the square of the degree of decomposition. The initial rate is proportional to the square of the concentration of HNO3 formed due to dissociation of the salt. The activation energy of this process is 15.3±1.8 kcal/mol. It is suggested that the initial stage the process proceeds via interaction between N2O3 and NH3OH+, whereas the subsequent acceleration is due to oxidation of NH3OH+ by nitrogen oxides formed as well as by nitrous acid.
20 citations
TL;DR: The benzyl radical C6H5CH2 has been obtained by gas phase pyrolysis of two different precursors, benzyl bromide and dibenzyl, and studied in an argon matrix at 12 K by IR spectroscopy.
Abstract: The benzyl radical C6H5CH2 has been obtained by gas phase pyrolysis of two different precursors, benzyl bromide and dibenzyl, and studied in an argon matrix at 12 K by IR spectroscopy. Similarly, the deuterosubstituted benzyl radicals, C6H5CD2 and C6D5CH2, have been investigated. The assignment of the IR bands of the benzyl radical and its deuteroanalogs to fundamental modes and a calculation of the valence force field have been performed. The obtained data give evidence of sp2 hybridization of the methylene carbon atom and delocalization of the electron density between the ring and the CH2 group, and are in good agreement with the planar structure of the radical.
19 citations
TL;DR: In addition, diphosphinomethanides are useful ligands to promote high coordination numbers with main-group elements (mule hypervalent compoundsmule), transition or lanthanoid metals.
Abstract: Phosphinomethanides bind to electrophilesvia either phosphorus or carbon. The resulting compounds usually are unstable and/or can rearrange from carbon to phosphorus coordination orvice versa. Selective oxidative coupling reactions of the phosphinomethanide ligands are found with metal centers in high oxidation states, but these ligands are stable to reduction. Thus, low-valency species can be stabilized. In addition, diphosphinomethanides are useful ligands to promote high coordination numbers with main-group elements (mulehypervalent compoundsmule), transition or lanthanoid metals.
19 citations
TL;DR: In this paper, the multiple-attuned total reflection (MATR) IR-spectra of HCl solutions in DMF (0.48% HCl) were recorded and analyzed in the range of 900-4000 cm−1.
Abstract: The Multiple Attenuated Total Reflection (MATR) IR-spectra of HCl solutions in DMF (0–48.55% HCl) were recorded and analyzed in the range of 900–4000 cm−1. Depending on the ratio of compounds, a variety of complexes (2 DMF) · HCl (1), DMF · HCl (2), DMF · (2 HCl) (3) are formed in the system. The concentrations of the complexes were measured. Complex2 possesses a quasi-ionic structure Me2NHCO...H...Cl. The addition of a DMF molecule to complex2 with formation of complex1 does not result in destruction of the quasi-ionic structure of the DMF-HCl bond. In excess HCl, this structure is decomposed and the complex with the ion pair structure Me2NHCOH+ (ClHCl)− is formed.
19 citations
TL;DR: In this article, it was shown that reactions with the retention of the N-N-group (azo coupling, formation of triazenes and azides) are typical of aminofurazans and 4-aminofuroxans (2) with nitrosylsulfuric acid in a mixture of conc. H2SO4 and H3PO4 is not typical.
Abstract: Diazotization of aminofurazans (1) and 4-aminofuroxans (2) with nitrosylsulfuric acid in a mixture of conc. H2SO4 and H3PO4 has been studied and offered as a general method for preparing furazanyl- (3) and furoxanyldiazonium (4) salts. It has been shown that reactions with the retention of the N-N-group (azo coupling, formation of triazenes and azides) are typical of salts3 and4, while elimination of the N2 molecule (Sandmeyer reaction, hydrolysis, reduction) is not typical.
TL;DR: In this paper, the characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2− was performed using 17O,23Na,35Cl,133Cs NMR and UV spectroscopy.
Abstract: The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2− was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2]
n
·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.
TL;DR: In this paper, the products of vacuum pyrolysis of bis(cyclopentadienyl)nickel have been studied by matrix isolation infrared spetroscopy, and three IR bands at 3079, 1383 and 661 cm−1 corresponding to the cyclopentadieneyl radical have been observed.
Abstract: The products of vacuum pyrolysis of bis(cyclopentadienyl)nickel have been studied by matrix isolation infrared spetroscopy. Three IR bands at 3079, 1383 and 661 cm−1 corresponding to the cyclopentadienyl radical have been observed. A comparison of the IR spectrum of the radical C5H5 with those of the ligand π-C5H5 and free anion−C5H5 has been performed.
TL;DR: In this paper, the authors derived from topology and graph theory indicate that the deltahedral boranes and carboranes may be regarded as three-dimensional delocalized aromatic systems in which surface bonding and core bonding correspond to σ-bonding and πbonding, respectively, in planar polygonal two-dimensional hydrocarbons.
Abstract: Methods derived from topology and graph theory indicate that the deltahedral boranes B
n
H
n
2− and the corresponding carboranes C2Bn−2H
n
(6 ≤n ≤ 12) may be regarded as three-dimensional delocalized aromatic systems in which surface bonding and core bonding correspond to σ-bonding and π-bonding, respectively, in planar polygonal two-dimensional hydrocarbons CinnH
n
(n−6)+ (n=5/7). The two extreme types of topologies which may be used to model core bonding in deltahedral boranes and carboranes are the deltahedral (D
n
) topology based on the skeleton of the underlying deltahedron and the complete (K
n
) topology based on the corresponding complete graph. Analyses of the Hoffmann-Lipscomb LCAO extended Huckel computations, the Armstrong—Perkins—Stewart self-consistent molecular orbital computations, and SCF MOab initio GAUSSIAN-82 computations on B6H6
2− indicate that the approximation of the atomic orbitals by the sum of the molecular orbitals, as is typical in modernab initio computations, leads to significantly weaker apparent core bonding approximated more closely by deltahedral (D
n
) topology than by complete (K
n
) topology.
TL;DR: In this article, the product of the reaction between anhydrous lanthanum trichloride and potassium vinylsiloxanolate, K5[VinSiO2]8La4(μ4-OH)[O2SiVin]8 · 5n-BuOH·2H2O has been studied by X-ray diffraction.
Abstract: The product of the reaction between anhydrous lanthanum trichloride and potassium vinylsiloxanolate, K5[VinSiO2]8La4(μ4-OH)[O2SiVin]8 · 5n-BuOH·2H2O has been studied by X-ray diffraction. The compound is a «sandwich»-type complex where macrocyclic vinyloctasiloxanolate ligands with regularcis-configuration have co-axial and antiparallel orientation. These ligands coordinate a planar «cationic layer» formed by four La3+ ions and stabilized by an additional μ4-OH− bridge ligand. A three-dimensional cage structure of complex lanthansiloxanolate pentaanions linked through the coordinated K+ counter-ions is formed in the crystal studied.
TL;DR: Triphenylbismuth diacylates, Ph3Bi(O2CR)2 (R = Me, Et, Ph, CF3, CH=CH2), are novel effective reagents for fine organic synthesis as mentioned in this paper.
Abstract: Triphenylbismuth diacylates, Ph3Bi(O2CR)2 (R = Me, Et, Ph, CF3, CH=CH2), are novel effective reagents for fine organic synthesis. They oxidize primary and secondary alcohols and di-tert-glycols under mild conditions to form the corresponding carbonyl compounds in high yields;O- andN-phenylate alcohols, enols, and amines; andO- ando-C-phenylate phenols.
TL;DR: In this article, the authors showed that lithium phenylacetylide with triphenylborane and diphenylchlorophosphine gave 1-diphenylboryl-2-dipphenylphosphino-1, 2-Diphenylethene, which is less reactive than dialkylborylphosphineethenes.
Abstract: Consecutive interaction of lithium phenylacetylide with triphenylborane and diphenylchlorophosphine gave 1-diphenylboryl-2-diphenylphosphino-1,2-diphenylethene, which is less reactive than dialkylborylphosphinoethenes
TL;DR: In this article, an X-ray structural investigation of the interaction products of anhydrous trivalent neodymium, gadolynium, and dysprosium chlorides with sodium phenylsiloxanolate was carried out.
Abstract: An X-ray structural investigation of the interaction products of anhydrous trivalent neodymium, gadolynium, and dysprosium chlorides with sodium phenylsiloxanolate was carried out. The synthesized compounds with the general formula Na6[PhSiO2]8M4(μ4-O)[O2SiPh]8 · 10EtOH · 8H2O (M = Nd, Gd, Dy) were found to be isomorphous isostructural sandwich complexes. The macrocyclic octaphenyloctasiloxanolate ligands in the complexes have anall-cis-configuration and are arranged in co-axial antiparallel pairs and coordinate the square planar groups of the four Nd3+, Gd3+, or Dy3+ ions stabilized by an additional central μ4-bridging O2− ligand. Six Na+ counterions form the outer coordination sphere of the complexes such that four of them coordinate the siloxane macrocycle O atoms in pairs in analogy with crown-ether complexes.
TL;DR: In this article, an improved preparative method for the synthesis of oligo(ethylene glycol) bis[2-(diphenylphosphinoyl)ethyl] ethers has been developed.
Abstract: An improved preparative method for the synthesis of oligo(ethylene glycol) bis[2-(diphenylphosphinoyl)ethyl] ethers has been developed. The complex-forming ability of these ligands toward alkali-metal cations has been studied by conductometry in anhydrous MeCN at 25°C. Ligands of this type have been shown to be highly efficient and selective complexing agents with respect to the Li+ cation. The stability series of the complexes M+L has the form Li > Na > K > Rb in all cases. The complexing properties and selectivity displayed by these new monopodands in MeCN have been compared with those in the THF-CHCl3 (4∶1) system studied previously.
TL;DR: Aromatic hydrocarbons are oxidized with hydrogen peroxide in the presence of catalytic amounts of VO3− and pyrazine-2-carboxylic acid into phenols or into quinones.
Abstract: Aromatic hydrocarbons are oxidized with hydrogen peroxide in the presence of catalytic amounts of VO3
− and pyrazine-2-carboxylic acid into phenols (provided excess hydrocarbon is used) or into quinones (at high H2O2 concentrations). 2-Propanol, ethanol, cyclohexanol, and benzyl alcohol are transformed into the corresponding aldehydes and ketones under the same conditions (without a solvent or in MeCN).
TL;DR: Ion exchange interaction of the monolayer aqueous dispersion obtained by hydration of crystalline LiMoS2 with Li, Na, K salts and alkyiammoniiim halides is studied in this paper.
Abstract: Ion-exchange interaction of the monolayer aqueous dispersion obtained by hydration of crystalline LiMoS2 with Li, Na, K salts and alkyiammoniiim halides is studied. Intercalation compounds of MoS2 with hydrated inorganic cations as well as hitherto unattainable intercalation compounds of MoS2 with alkylammonium cations are shown to be formed under these conditions. The composition and structure of these compounds are investigated.
TL;DR: In this paper, an asymmetric Michael addition of methyl nitroacetate to crotonaldehyde catalyzed by chiral amines was carried out, and the maximum chemical yield of diastereomeric products amounted to 95 %.
Abstract: The asymmetric Michael addition of methyl nitroacetate to crotonaldehyde catalyzed by chiral amines was carried out. The maximum chemical yield of diastereomeric products amounted to 95 %. The best asymmetric induction (42 % e.e.) was achieved in the case of catalysis by (S)-prolinol. The diastereomeric mixture was converted to a mixture of stereoisomeric 3-methyl-2-methoxycarbonylpyrrolidines. Absolute configurations of (2S,3S)-and (2R,3S)-isomers formed in excess were determined using GLC by comparison with authentic samples of racemic and optically pure forms of 3-methylproline.
TL;DR: In this article, the enthalpies of azobenzene in a melt and in solution results in the formation of aniline and the possible directions of the reaction are considered.
Abstract: Thermolysis of azobenzene in a melt and in solution results in the formation of aniline. The possible directions of the reaction are considered. Comparison of the enthalpies of the reaction proves that the cleavage of a π-bond in the N=N group to form a biradical intermediate is thermodynamically more favorable than that of a C-N π-bond.
TL;DR: In this article, a theoretical basis for calculating parameters of the pore structure of active carbons is considered, and the parameters of micro- and mesopores of different countries have been determined from benzene vapor adsorption isotherms at 293 K.
Abstract: A theoretical basis for calculating parameters of the pore structure of active carbons is considered. Active carbons are classified into four types according to their dispersion and mesopore surface areas. The parameters of micro- and mesopores of active carbons produced in different countries have been determined from benzene vapor adsorption isotherms at 293 K. The differences in parameters of the Dubinin—Stoeckly equation found from adsorption isotherms of different compounds are noted.
TL;DR: In this paper, the IR and Raman spectra of 1,4-butanediol (BD) versus variations in the medium (CCl4, CH3CN), concentration, temperature, and phase state were obtained.
Abstract: IR and Raman spectra of 1,4-butanediol (BD) versus variations in the medium (CCl4, CH3CN), concentration, temperature, and phase state were obtained. The observed changes attest to the conformational variety of BD molecules under the experimental conditions. On the basis of the analysis of the v(OH) region it is concluded that both in the gas phase and in CCl4 solution conformers of BD with free OH groups coexist with conformers with O-H...O intramolecular hydrogen bonds. The difference in enthalpies, ΔH, for the groups of conformers with and without intramolecular hydrogen bonds was found from the temperature dependence of the v(OH)free and v(OH)intra band intensities. The structures and energies for 70 possible spectrally and energetically distinguishable conformers of BD that do not take into account intramolecular hydrogen bonds were calculated by molecular mechanics with account of electron lone pairs of oxygen atoms. Using the experimental values of ΔH and the calculated relative conformer energies,E, the intramolecular hydrogen bond energyEintra= 3.7 kcal mol−1 was found.