Radiolysis of water-nitrobenzene-carbon tetrachloride and water-chlorobenzene-carbon tetrachloride two-phase systems. Radiation yields of chloride ions

The influence of nitrobenzene and chlorobenzene on the total radiation yield of chloride ions in the -irradiation of water-carbon tetrachloride two-phase systems has been determined. Nitrobenzene at small concentrations shows a pronounced protective influence on the radiation destruction of carbon tetrachloride. Similar protective effect on the destruction of carbon tetrachloride is shown by chlorobenzene, too, but the decrease of radiation yields of chloride ions is smoother, which is explained by radiation decomposition of chlorobenzene itself. Protective effect of nitrobenzene and chlorobenzene on the radiation destruction of carbon tetrachloride is explained by transfer of energy from carbon tetrachloride molecules to the aromatic molecules.     

Use of dichloromethane with dithizone as an alternative solvent to carbon tetrachloride restricted by Montreal protocol

The spectral characteristics of dithizone and its metal complexes were measured in dichloromethane as an alternative solvent to carbon tetrachloride which will be illegal to manufacture by the year 2000, according to the revised Montreal Protocol. The extraction equilibria of its metal complexes were also reported and discussed. Dichloromethane was found to enhance the sensitivity of dithizone towards Co(II), Cu(II), Hg(II), Pb(II), Zn(II), Bi(III), Ag(I), In(III) and Tl(I). It was also found to be a better solvent than carbon tetrachloride for the separation of Cd(II) from Zn(II) and for the separation of Co(II) from Ni(II).     

Charge Transfer Complex Role in the Formation of Chlorobenzene in the γ‐Irradiated Carbon Tetrachloride‐Benzene System

The formation of carbon tetrachloride‐benzene charge transfer complex was confirmed by UV and NMR spectrometric studies. A change in UV spectrum of benzene is observed upon addition of carbon tetrachloride. Whereas the appearance of new bands supports the formation of charge transfer complex. NMR study shows that, chemical shift of benzene pmr signal depends on the CCl₄‐C₆H₆ molar ratio. This observation is another criterion for the formation of benzene‐carbon tetrachloride charge transfer complex. Job's Continuous Variation method indicates that a 2:1 CCl₄‐C₆H₆ charge transfer complex (2:1 CTC) is formed. The association constants (K_2:1) of (2:1 CTC) was found to be 0.0197 M^?2. The maximum concentration of (2:1 CTC) was found to be in samples with 2:1 CCl₄‐C₆H₆ molar ratio (33% benzene mole). On the other hand the maximum yield of chlorobenzene was obtained, also, upon radiolysis of CCl₄‐C₆H₆ samples at a 2:1 molar ratio (33% benzene mole). Therefore, it could be concluded that (2:1 CTC) participates in the formation of chlorobenzene upon radiolysis of the benzene‐carbon tetrachloride system. This conclusion was supported by the dependence of the chlorobenzene yield of a γ‐irradiated carbon tetrachloride‐benzene system (2:1 molar ratio) on irradiation time according to a third order kinetic equation with a very good linearity (R² = 0.9977). Accordingly, the rate constant for the chlorobenzene formation under this condition was found to be ≈ 5.5 × 10^?7 L².mol^?2.h^?1. We propose a radiation chemical mechanism in which the 2:1 CTC plays a role in the formation of chlorobenzene.     

Characterization of polychlorinated aromatic hydrocarbons by reversed-phase liquid chromatography with ultraviolet absorbance and mass spectrometric detection

Ten polychlorinated aromatic hydrocarbons (PCAHs), perchlorobenzene (I), perchlorobiphenyl (II), perchlorobenzo[f]inden-1-one (III), perchloronaphthalene (IV), perchloropenta[def]phenanthren-4-one (V), 6H-1,2,4,5,7,8,9,10,11-nonachlorobenzo[cd]pyrene-3-one (VI), perchloroacenaphthylene (VII), 6-(p-tolyl)-6H-1,2,3,4,5,7,8,9,10,11-decachlorobenzo[cd]pyrene (VIII), perchlorofluoranthene (IX) and 6-(p-tolyl)-6H-1,11-dihydroxy-2,3,4,5,7,8,9,10-octachlorobenzo[cd]pyrene (X) have been separated with reversed-phase liquid chromatography (RPLC) by using two gradient eluents (toluene/methanol and cyclohexane/methanol), and were detected by ultraviolet (UV) and mass spectrometry (MS). The separation and detection of half of these ten compounds, which are of extremely high molecular weights, is an improvement over the chromatographic analysis of PCAHs. When the procedure was applied to the analysis of PCAHs of the products from the combustion of chlorobenzene and carbon tetrachloride, I, II, IV, VIII and X could be detected.     

Well-defined nanoporous palladium for electrochemical reductive dechlorination

Well-defined nanoporous palladium (np-Pd) fabricated by a modified electrochemical dealloying procedure is demonstrated to be an excellent electrocatalyst material for reductive degradation of both carbon tetrachloride and chlorobenzene.     

Carbon tetrachloride-induced crack healing in polycarbonate

Crack healing induced by carbon tetrachloride in polycarbonate has been studied at temperatures in the range of 40–60°C. The carbon tetrachloride treatment reduces the glass transition temperature of polycarbonate. Crack healing is observed because the effective glass transition temperature in polycarbonate is reduced to below the test temperature by the carbon tetrachloride treatment. Two distinctive stages of crack healing are divided based on the recovery of mechanical strength and fractograph. The first stage corresponds to the progressive healing due to the convolution of wetting and self-diffusion, which has a constant crack closure rate. Immediately following the first stage, the second stage, corresponding to the self-diffusion of polymer chain, enhances the quality of healing behavior. The transport of carbon tetrachloride in polycarbonate consists of case I (concentration gradient controlled) and case II (relaxation controlled) behaviors. The direction of case II is opposite to that of case I. The solubility decreases with increasing temperature, but diffusivity and velocity for mass transfer, crack closure rate, and diffusion coefficient for the diffusion front have the opposite trend. The first stage of crack healing is controlled by case II transport. The transport of carbon tetrachloride changes the fracture behavior of polycarbonate from ductile to brittle. A comparison of crack healing in polycarbonate and poly (methyl methacrylate) is made. © 1994 John Wiley & Sons, Inc.     

Extraction of cobalt(II) from aqueous thiocyanate solutions by tri-n-octylamine

The distribution of cobalt(II) between acidic thiocyanate solutions and tri-n-octylainine dissolved in various diluents has been measured for several cobalt(II) loadings and amine concentrations. Diluents investigated included n-hexane, cyclohexane, benzene, xylene, carbon tetrachloride, chloroform, chlorobenzene, o-dichlorobenzene and nitrobenzene. In all cases, the species extracted is bis(tri-n-octylammonium) tetrathiocyanatocobaltate(II). The ability of each diluent to extract cobalt(II) from acidic thiocyanate solutions is approximately correlated with the dielectric constant of the pure diluent, i.e., the smaller the dielectric constant, the larger the distribution ratio, with the exceptions of nitrobenzene and chloroform.     

Excess volume of mixing of some polar and nonpolar liquids with propylene carbonate

The excess volume of mixing as a function of composition has been measured at 30°C and 40°C for mixtures of propylene carbonate with nitrobenzene, chlorobenzene, benzene, toluene, cyclohexane, dioxane, carbon tetrachloride, and chloroform. The highly polar nitrobenzene forms an ideal mixture with propylene carbonate. Chloroform, carbon tetrachloride, dioxane, chlorobenzene, benzene, and toluene give negative volume changes on mixing. In mixtures with cyclohexane,V _m ^E is positive at lower mole fractions of cyclohexane but becomes negative as the mole fraction of cyclohexane increases.     

以N-杂环卡宾为配体的金属络合物催化有机合成的反应

综述了近几年来以N-杂环卡宾为配体的金属络合物催化有机合成的反应。     

New synthesis routes to 2-halopyridines. II. 2-bromopyridine

The use of bromine chloride (equilibrium mixture) in substitution reactions has been extended to heterocyclic substrates. The vapor phase bromination of pyridine (I) with bromine chloride at temperatures as low as 375° (carbon tetrachloride diluent) gave the following product distribution: 2-bromopyridine (IV) (75%) > 2-chloropyridine (VI) (21%) > 3-bromopyridine (II) (2.0%) ? 2,6-dibromopyridine (VI) (1.5%). In contrast, when bromine was employed in place of bromine chloride (450°; carbon tetrachloride diluent), product orientation was significantly altered to give nearly equal quantities of 3-bromopyridine (II) (17%) and 2-bromopyridine (IV) (22.7%).     

4-Vinylpyridine-Modified Nickel and Cobalt Dibenzoylmethanates as New Hosts: Inclusions with Carbon Tetrachloride and Chlorobenzene

Abstract

Bis(4-vinylpyridine)bis(dibenzoylmethanato)metal(II), [M(ViPy)₂(DBM)₂] (M = Ni(II), Co(II); ViPy = 4-Vinylpyridine; DBM = C₆H₅COCHCOC₆H₅ ^?, dibenzoylmethanate) is a new metal-complex host. Its inclusions with carbon tetrachloride (host:guest = 1:2; triclinic, P 1, Z = 1) and chlorobenzene (host:guest = 1:1; monoclinic, P2 ₁ /c, Z = 4) are consistent with the van der Waals packing of neutral complex (host) and solvent (guest) molecules. In the host unit, four oxygens from two chelate DBM-units provide a square-planar environment around the metal center that is extended to octahedral coordination by two apical nitrogens from two vinylpyridine moieties in the trans-position. In the carbon tetrachloride inclusions, the host traps two guest molecules in large prolate spheroidal cavities. In the chlorobenzene inclusions, guest species are located inside 8-shaped serpentine channels along the y-axis. The nickel and cobalt versions of the inclusion compounds were found to be very similar.     

Homolytic displacement at carbon: XI. Intramolecular homolytic displacement as a route to cyclopentane and tetrahydrofuran derivatives from hex-5-enyl- andhex-3-oxo-5-enylcobaloximes

5-Methylhex-5-enylcobaloxime reacts with carbon tetrachloride and with fluorotrichloromethane at 80–100°C to give substantially pure 1-methyl-1-(β,β,β-trichloroethyl)- and 1-methyl-1-β-fluoro-β,β-dichloroethyl)-cyclopentane. Hex-5-enylco-baloxime also gives trichloroethylcyclopentane from carbon tetrachloride, but the yield is dependent on the concentration of carbon tetrachloride. Similar cyclisation to give trichloroethyl- or fluorodichloroethyltetrahydrofuran is observed in the reactions of hex-3-oxo-5-enylcobaloxime with carbon tetrachloride and fluorotrichloromethane. However, no cyclisation was observed in the reactions of the ester, hex-2-one-3-oxo-5-enylcobaloxime, with carbon tetrachloride. These reactions are believed to take place by attack of a polyhalogenomethyl radical at the terminal unsaturated carbon of the organic ligand, followed either by an intramolecular homolytic displacement in which the carbon radical at position-5 attacks carbon-1 with displacement of cobaloxime(II), or by a halogen atom abstraction.     

Effect of Electron Scavengers on the Chain Reaction of Sulfo-Group Substitution for Bromine in 1-Bromo-2-hydroxynaphthalene Photosensitized with Tris(2,2′-bipyridyl)ruthenium(II)

The effect of electron scavengers (carbon tetrachloride, chloroform, and chloranil) on the chain radical-ion reaction of sulfo-group substitution for bromine in 1-bromo-2-hydroxynaphthalene photosensitized with a tris(2,2′-bipyridyl)ruthenium(II) complex was studied in an aqueous solution of sodium sulfite. It was found that “ sacrificial” electron scavengers enhanced the quantum yield of the photosensitized substitution reaction. Using the flash photolysis technique, it was shown that the electron scavengers reacted with the ruthenium(I) complex formed as a result of dissociation of a radical-ion pair in the initiation step. The rates constants for the reaction of chloroform, carbon tetrachloride, and chloranil with the ruthenium(I) complex are 1.5 × 10⁴, 1.2 × 10⁷, and 1.5 × 10⁹ dm³ mol⁻¹ s⁻¹, respectively. The chain length of the substitution reaction in aqueous solution in the presence of carbon tetrachloride is 220 ± 20.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 353–357.Original Russian Text Copyright © 2005 by Ivanov Lyashkevich.     

Novel solvent effects in the photopolymerization of methyl methacrylate by use of quinoline–bromine charge-transfer complex as photoinitiator

Photopolymerization of MMA was carried out at 40°C in diluted systems by use of quinolinebromine (Q–Br₂) charge-transfer complex as the initiator and chloroform, carbon tetrachloride, chlorobenzene, dioxane, THF, acetone, benzene, toluene, quinoline, and pyridine as solvents. The results showed variable monomer exponents ranging from 1 to 3. For chloroform, carbon tetrachloride, and chlorobenzene, the monomer exponent observed was unity; for other solvents used, the value of the same exponent was much higher (between 2 and 3). Initiation of polymerization is considered to take place through radicals generated in the polymerization systems by the photodecomposition of (Q–Br₂)–monomer complex (C) formed instantaneously in situ on addition of the Q–Br₂ complex in monomer. The kinetic feature of high monomer exponent is considered to be due to higher order of stabilization of the initiating complex (C) in presence of the respective solvents. In the presence of the retarding solvents, very low or zero initiator exponents were also observed, depending on the nature and concentration of the solvents used. The deviation from the square-root dependence of rate on initiator concentration becomes higher at high solvent and initiator concentrations in general. This novel deviation is explained on the basis of initiator termination, probably via degradative chain transfer involving the solvent-modified initiating complexes and the propagating radicals.     

Studies on 3,3′-dichloro-, 4,4′-dichloro- and 5,5′-dichloro,2-2′-dimethyldithizone and their reactions with metal ions

Three new derivatives of dithizone are reported, with their electronic and i.r. spectra, acidity constants and partition coefficients between 0.5 M sodium perchlorate and chloroform or carbon tetrachloride. The extraction equilibria with Cd, Co(II), Hg(II), Ni, Pb, Tl(I), Zn and Bi and the spectrophotometric characteristics of the extractable metal chelates are described. Complete extraction of these complexes requires higher pH than that needed with dithizone itself. The 4,4′-dichloroisomer is more efficient than the 3,3′ and 5,5′-isomers, or dithizone itself, for the separation of cadmium from zinc or cobalt from nickel.     

FT-IR study of self-association of some hydroperoxides

Self-association of cumyl, tertiary butyl and 3-phenylmethyl hydroperoxides in solutions of n-decane, carbon tetrachloride and chlorobenzene were studied by IR spectroscopy (3100–3700 cm⁻¹, 293–353 K). The experimental data were interpreted by factor analysis and band contour resolution. The di- and trimerization constants and thermodynamic parameters of self-associates were determined. Intramolecular hydrogen bond of cumyl hydroperoxide was investigated. The conformations of tertiary butyl and cumyl hydroperoxides were studied. The solvent influence on the thermodynamic parameters of hydrogen bond was found.     

Determination of dipole moment in the ground and excited state by experimental and theoretical methods of N-nonyl acridine orange

The absorption and fluorescence spectra of N-nonyl acridine orange are determined at room temperature (298 K) in cyclohexane, benzene, carbon tetrachloride, chloroform, chlorobenzene and dichloromethane. The ground state of dipole moment was obtained by impedance measurements using Guggenheim-Debeye's method. The experimental excited state dipole moment of N-nonyl acridine orange was determined using Bakhshiev's and Kawski-Chamma-Viallet's formulae and solvent polarity parameter proposed by Reichardt. These experimental results were completed with theoretical results using quantum chemical methods. The experimental (muexp=10.76 D) and theoretical (mucal=9.9 D) dipole moments in the ground and excited state (muexp*=14.56 D) were compared.     

Kinetics of α-olefin metathesis on binary and ternary catalytic systems based on MoCl<Subscript>5</Subscript>/SiO<Subscript>2</Subscript>: Determination of the number of active centers and the mechanisms of their formation,deactivation, and reactivation

The kinetics of α-olefin metathesis in the presence of binary (MoCl₅/SiO₂-Me₄Sn) and ternary catalytic systems (MoCl₅/SiO₂-Me₄Sn-ECl₄, E = Si or Ge) was studied. It was found that reactivation in the course of metathesis occurred on the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5–6% of the amount of Mo), and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The roles of the individual components of the catalytic systems were revealed.     

Medicinal foodstuffs. XXV. Hepatoprotective principle and structures of ionone glucoside, phenethyl glycoside, and flavonol oligoglycosides from young seedpods of garden peas, Pisum sativum L

A new ionone glucoside, pisumionoside, a phenethyl glycoside, sayaendoside, and two acylated flavonol oligoglycosides, pisumflavonosides I and II, were isolated from the young seedpods of garden peas, Pisum sativum L., together with quercetin and kaempferol 3-O-(6-O-trans-p-coumaroyl)-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosides and quercetin and kaempferol 3-sophorotriosides. The structures of pisumionoside, sayaendoside, and pisumflavonosides I and II were determined on the basis of chemical and physicochemical evidence, respectively. Quercetin 3-sophorotrioside, a principle component, was found to show protective effects on liver injury induced by D-galactosamine and lipopolysaccharide and by carbon tetrachloride in mice.     

Photopolymerization of methyl methacrylate using triethylene tetramine-benzophenone combination as the photoinitiator

Photopolymerization of MMA at 40 was studied using triethylene tetramine (TETA)-benzophenone (BP) combination as the initiator. Initiator exponent is 0.5; monomer exponent is 1.0 in benzene, toluene, chlorobenzene, acetone and methyl ethyl ketone, < 1.0 in halomethanes (chloroform and carbon tetrachloride) and > 1 in methanol. Photoreduction of BP1(BP in the excited state) by ground state TETA via an exiplex formation is considered to produce chain-initiating radicals. Polymers obtained were found to bear amine end-groups. Termination takes place bimolecularly (initiator exponent being 0.5 in bulk as well as in diluted systems). The radical generation process is dependent on the nature of the solvent. The role of solvents in modifying the initiation or radical generation process has been examined and analysed.