- Effect of ultrasound on the photolysis of carbon tetrachloride mediated by benzothiazole derivatives. 2-Sulfanylbenzothiazoles
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The photodecomposition of carbon tetrachloride was studied under sonication in the presence of N-(tert-butyl)-benzothiazole-2-sulfenamide (TBBS), N-(cyclohexyl)benzothiazole-2-sulfenamide (CBS), and 2-sulfanylbenzo-thiazole (MBT) as electron donors. By following the concentrations of Cl- and C2Cl6 as a function of time, it was shown that ultrasound decreases their rate of formation when TBBS and CBS were used, but it has no effect in the presence of MBT These observations were rationalized by a cavitation-induced destabilization of the contact ion pair (CIP) formed from exciplexes.
- Gaplovsky, Anton,Toma, Stefan,Luche, Jean-Louis,Jakubikova, Bibiana,Gaplovska, Katarina,Mracnova, Renata
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- Reaction of Tetrathiafulvalene with Haloalkanes
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A kinetic study of the photochemical rection of TTF with haloalkanes has been made.The results are largely in agreement with a mechanism suggested by Scott and co-workers, but some additional findings of fundamental importance were obtained.An improved photosynthesis of TTFCl0.68 is reported.
- Vessal, Behnam,Miller, John G.
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- Sonoluminescence and Sonochemical Reactions of Aqueous Carbon Tetrachloride Solutions
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The sonoluminescence intensity and its spectral distribution, and the sonochemical yields from saturated aqueous solutions of carbon tetrachloride, were measured simultaneously.The variation of these quantities with static pressure was also determined for
- Chendke, P. K.,Fogler, H. S.
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- Interaction of trichloromethane and tetrachloromethane with nitrogen trifluoride
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Interaction of nitrogen trifluoride with trichloromethane and tetrachloromethane at temperatures in the range from 20 to 200°C and pressures of up to 6.0 MPa in the gas and liquid phases was studied.
- Mukhortov,Pashkevich,Blinov,Kambur,Kambur,Petrov,Kurapova
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- High-Pressure Studies of Radical-Solvent Molecule Interactions in the CCl3 and Bromine Combination Reactions of CCl3
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The combination reactions CCl3 + CCl3 (+ M) → C2Cl6 (+ M) and CCl3 + Br (+ M) → CCl 3Br (+ M) (with rate constants of k1 and k2, respectively) were studied at temperatures of 250 and 300 K over the pressure range of 0.01-1000 bar. Helium, argon, xenon, N2, CO2, and SF6 were used as bath gases. CCl3 radicals were generated via the photolysis of CCl3Br at 248 nm, and their absorption was monitored at 223.5 nm. The limiting "high-pressure" rate constants within the energy-transfer mechanism were determined, independent of density and the choice of the bath gas, over the pressure range of 1-10 bar, to be k 1,∞(T) = (1.0 ± 0.2) × 10-11 (T/300 K)-0.17 cm3 molecule-1 s-1 and k2,∞(T) = (2.0 ± 0.2) × 10-11 (T/300 K)-0.13 cm3 molecule-1 s-1. In the helium, N, and argon bath gases, at pressures above ~40 bar, the reactions became increasingly faster when the pressure was further raised until they finally started to slow at densities where diffusion-controlled kinetics dominates. This is the first detailed report of such a peculiar density dependence of combination rate constants for larger radicals with five or eight atoms. Possible origins of these pressure effects, such as the influence of the radical-complex mechanism and the density dependence of electronic quenching, are discussed.
- Oum, Kawon,Luther, Klaus,Troe, Juergen
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- Reaction of carbon tetrachloride with the nanoscale particles of silver and copper in a liquid phase
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The nanoscale particles of silver and copper coated with amorphous carbon (Ag/C and Cu/C) react with liquid carbon tetrachloride at 25-30°C to selectively form hexachloroethane in 60% yield.
- Timoshenko, Vadim A.,Bogdanov, Alexey V.,Shabatina, Tatyana I.,Mysik, Alexey A.,Uimin, Mikhail A.,Ermakov, Anatoly E.,Sergeev, Gleb B.
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- Kinetic Study of the Reactions CCl3 + O2 + M -> CCl3O2 + M from 1 to 760 Torr and from 233 to 333 K
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The kinetics of reaction 1, CCl3 + O2 + M -> CCl3O2 + M, has been investigated in detail as a function of temperature and over a large pressure range.At low pressure, 0.8-12 Torr, the reaction was investigated by laser photolysis and time-resolved mass spectrometry, while at high pressure (760 Torr), flash photolysis with UV absorption spectrometry was employed.At the low pressure limit, the rate expression, k1(0) = (1.6 +/- 0.3) x 10-30(T/298)-(6.3+/-0.5) cm6 molecule-2 s-1 (M = N2), exhibits a quite strong negative temperature coefficient.The obtained strong collision rate expression, 7.0 x 10-30(T/298)-4.3 cm6 molecule-2 s-1, using either RRKM calculations or Troe's factorized expression, is unable to reproduce the experimental temperature dependence, unless an unreasonably strong temperature dependence is assigned to the collisional efficiency factor: βc = 0.23(T/298)-2.0 (M = N2).Similar results are obtained for other chlorofluoromethyl radicals.The falloff curves were constructed by using RRKM calculations obtained by adjusting βc and the transition-state model, in order to reproduce the experimental data.The rate expression at the high-pressure limit was derived from these calculations k1(infinite) = (3.2 +/- 0.7) x 10-12(T/298)-(1.2+/-0.4) cm3 molecule-1 s-1.All the parameters to be used in Troe's analytical expression for calculating the bimolecular rate constant at any pressure and temperature are given.The rate constant at the low-pressure limit k1(0) is more than an order of magnitude lower than for the CF3 radical.The RRKM calculations show that this arises from a large difference in the C-C bond dissociation energies in the corresponding peroxy radicals: 81.9 kJ mol-1 for CCl3O2 instead of ca. 145 kJ mol-1 for CF3O2.
- Danis, F.,Caralp, F.,Rayez, T.,Lesclaux, R.
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- Photocatalysis of chloroform decomposition by hexachloroosmate(IV)
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Hexachloroosmate(IV) effectively catalyzes the photodecomposition of chloroform in aerated solutions. The decomposition products are consistent with a mechanism in which excited state OsCl62- reduces chloroform, rather than one involving photodissociation of chlorine atoms. Trace amounts of ethanol or water in the chloroform lead to photosubstitution to form OsCl5(EtOH)- or OsCl5(H2O) -, neither of which is photocatalytically active.
- Pena, Laura A.,Hoggard, Patrick E.
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- Synthesis of Decorated Carbon Structures with Encapsulated Components by Low-Voltage Electric Discharge Treatment
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Abstract: Polycondensation of complexes of chloromethanes with triphenylphosphine by the action of low-voltage electric discharges in the liquid phase gives nanosized solid products. The elemental composition involving the generation of element distribution maps (scanning electron microscopy–energy dispersive X?ray spectroscopy mapping) and the component composition (by direct evolved gas analysis–mass spectrometry) of the solid products have been studied. The elemental and component compositions of the result-ing structures vary widely depending on the chlorine content in the substrate and on the amount of triphenylphosphine taken. Thermal desorption analysis revealed abnormal behavior of HCl and benzene present in the solid products. In thermal desorption spectra, these components appear at an uncharacteristically high temperature. The observed anomaly in the behavior of HCl is due to HCl binding into a complex of the solid anion HCI-2 with triphenyl(chloromethyl)phosphonium chloride, which requires a relatively high temperature (up to 800 K) to decompose. The abnormal behavior of benzene is associated with its encapsulated state in nanostructures. The appearance of benzene begins at 650 K and continues up to temperatures above 1300?K.
- Bodrikov, I. V.,Pryakhina, V. I.,Titov, D. Yu.,Titov, E. Yu.,Vorotyntsev, A. V.
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- Revisiting Alkane Hydroxylation with m-CPBA (m-Chloroperbenzoic Acid) Catalyzed by Nickel(II) Complexes
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Mechanistic studies are performed on the alkane hydroxylation with m-CPBA (m-chloroperbenzoic acid) catalyzed by nickel(II) complexes, NiII(L). In the oxidation of cycloalkanes, NiII(TPA) acts as an efficient catalyst with a high yield and a high alcohol selectivity. In the oxidation of adamantane, the tertiary carbon is predominantly oxidized. The reaction rate shows first-order dependence on [substrate] and [NiII(L)] but is independent on [m-CPBA]; vobs=k2[substrate][NiII(L)]. The reaction exhibited a relatively large kinetic deuterium isotope effect (KIE) of 6.7, demonstrating that the hydrogen atom abstraction is involved in the rate-limiting step of the catalytic cycle. Furthermore, NiII(L) supported by related tetradentate ligands exhibit apparently different catalytic activity, suggesting contribution of the NiII(L) in the catalytic cycle. Based on the kinetic analysis and the significant effects of O2 and CCl4 on the product distribution pattern, possible contributions of (L)NiII?O. and the aroyloxyl radical as the reactive oxidants are discussed.
- Itoh, Mayu,Itoh, Shinobu,Kubo, Minoru,Morimoto, Yuma,Shinke, Tomoya,Sugimoto, Hideki,Wada, Takuma,Yanagisawa, Sachiko
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p. 14730 - 14737
(2021/09/29)
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- Destruction of chemical warfare agent simulants by air and moisture stable metal NHC complexes
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The cooperative effect of both NHC and metal centre has been found to destroy chemical warfare agent (CWA) simulants. Choice of both the metal and NHC is key to these transformations as simple, monodentate N-heterocyclic carbenes in combination with silver or vanadium can promote stoichiometric destruction, whilst bidentate, aryloxide-tethered NHC complexes of silver and alkali metals promote breakdown under mild heating. Iron-NHC complexes generated in situ are competent catalysts for the destruction of each of the three targetted CWA simulants.
- Weetman, Catherine,Notman, Stuart,Arnold, Polly L.
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supporting information
p. 2568 - 2574
(2018/02/28)
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- PROCESS FOR THE PRODUCTION OF CHLORINATED METHANES
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The present invention provides processes for the production of chlorinated methanes via the direct chlorination of methane. The processes include a dehydrochlorination and/or chlorination step that converts up to 100% of the higher chlorinated alkanes in a process stream from the methane chlorination reaction into more highly chlorinated alkanes. These more highly chlorinated alkanes can be easily removed from the process stream. The use of a cost effective feedstream of crude methane is thus rendered possible, without additional capital expenditure for the sophisticated separation equipment required to separate ethane and other hydrocarbon components from the methane feed.
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Paragraph 0062; 0063; 064
(2017/04/11)
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- Photocatalytic Conversion of a FeCl3–CCl4–ROH System
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The photocatalytic transformations of carbon tetrachloride and aliphatic primary alcohols in the presence of iron trichloride and a molar ratio of components FeCl3: CCl4: ROH = 1: 300: 2550 were studied. CCl4 is transformed into chloroform and hexachloroethane after exposure to a mercury lamp (250 W) to the FeCl3–CCl4–ROH system at 20°C, whereas the primary ROH alcohols are selectively oxidized into acetals (1,1-dialkoxyalkanes). The maximum conversion of CCl4 reaches 80%. The kinetics and mechanism of the photocatalytic conversion of the FeCl3–CCl4–ROH system are considered.
- Makhmutov
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p. 695 - 700
(2018/03/08)
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- A process for the preparation of full chloroethone
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The invention discloses a preparation method of hexachloroethane. The preparation method comprises the following steps: introducing chlorine gas into hexachloro-1,3-butadiene to carry out reactions, wherein the weight ratio of the catalyst to hexachloro-1,3-butadiene is 0.001-0.1:1, the reaction temperature is 30 to 200 DEG C, and the reaction pressure is 0.1 to 3.0 MPa, stopping introducing chlorine gas when the reactor pressure start to rise, finishing the reactions when the reactor pressure does not fall after stopping the chlorine gas, introducing the reaction liquid into water, filtering, washing the product with water, then washing the product with alkali, drying, and finally carrying out sublimation to obtain the hexachloroethane product. The provided preparation method has the advantages of simple technology, mild reaction conditions, high reaction yield, and low cost.
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Paragraph 0028-0029
(2017/02/02)
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- Photocatalysis of Chloroform Decomposition by Tetrachlorocuprate (II) on Dowex 2-X8
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Heterogenized on a polystyrene anion exchange resin and in the presence of oxygen, CuCl24 catalyzes the photodecomposition of chloroform at wavelengths above 345 nm with greater efficiency than an equivalent amount in homogeneous solution. The reaction is proposed to proceed in two stages, the first stage yielding CCl4 and HO2 as products, the second consisting of a chain reaction resulting from the CuCl2 4-catalyzed photodissociation of CCl4, yielding phosgene with CCl3 radicals as chain carriers. Photodecomposition is retarded by added Cl, CH3CN, C6H12 or C2H5OH, which is ascribed to the displacement of CHCl3 molecules from the vicinity of the copper by attraction to the polystyrene matrix or to the alkylammonium cation sites.
- Harvey, Brent M.,Hoggard, Patrick E.
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p. 1234 - 1242
(2015/02/18)
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- Photocatalysis of chloroform decomposition by the hexachlororuthenate(IV) ion
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Dissolved hexachlororuthenate(IV) effectively catalyzes the photodecomposition of chloroform to hydrogen chloride and phosgene under near-UV (λ > 345 nm) irradiation, whereby RuCl62- is not itself photocatalytically active, but is photochemically transformed into a species that is active, possibly RuCl5(CHCl3)-. Conversion to a photoactive species during irradiation is consistent with the acceleration of the decomposition rate during the early stages and with the apparent inverse dependence of the decomposition rate on the initial concentration of RuCl62-. The displacement of Cl - by CHCl3 in the coordination sphere to create the photoactive species is consistent with the retardation of photodecomposition by both Cl- and H2O. The much smaller photodecomposition rate in CDCl3 suggests that C-H bond dissociation occurs during the primary photochemical event, which is also consistent with the presence of a CHCl3 molecule in the first coordination sphere. In the presence of RuCl62-, chloroform decomposes under near-UV irradiation to phosgene and hydrogen chloride. The photoactive species is suggested to be RuCl5(CHCl3) -.
- Chan, Alissa M.,Pena, Laura A.,Segura, Rosa E.,Auroprem, Ramya,Harvey, Brent M.,Brooke, Caroline M.,Hoggard, Patrick E.
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p. 274 - 279
(2013/07/31)
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- Catalysis of the photodecomposition of carbon tetrachloride in ethanol by an Amberlite anion exchange resin
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The chloride form of the polystyrene-divinylbenzene anion exchange resin Amberlite IRA-900 was found to catalyze the photodecomposition of carbon tetrachloride in ethanol at wavelengths above 350 nm. With sulfate, bromide, and perchlorate as counterions, the resin was inactive. The major products are acetaldehyde, phosgene, chloroform, and hydrogen chloride. The photoreaction is much slower under 1.0 atm O2 than under air, while in deoxygenated solutions it is also much slower and produces no phosgene. Much of the observed behavior can be explained by a model in which the poly(styrene-co- divinylbenzene) matrix absorbs light and transfers energy to CCl4, which undergoes photodissociation, assisted by a chloride ion to stabilize the chlorine atom as Cl2-. Two major reaction channels for the trichloromethyl radicals produced by photodissociation are proposed, one in which CCl3 abstracts hydrogen from ethanol and the other involving addition of O2 to form trichloromethylperoxy radicals.
- Hoggard, Patrick E.,Maldotti, Andrea
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experimental part
p. 243 - 249
(2011/02/16)
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- Chemically induced dynamic nuclear polarization and the mechanism of the reaction of Et3Al with CCl4 in the presence of transition metal complexes
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Integral effects of chemically induced 1H and 13C nuclear polarization are reported for the reaction of Et3Al with CCl4 catalyzed by Pd(acac)2, Cu(acac)2, and Cp2TiCl2; for the reaction of (n-C8H 17)3Al with CCl4 in the absence of a catalyst and in the presence of Ni(acac)2; and for the reaction of the cyclic organoaluminum compound 1-ethyl-3-butylaluminacyclopentane with CCl4 in the presence of Pd(acac)2. A scheme of the catalytic cycle of this reaction predicting the formation of both radical and nonradical products is derived from the observed chemically induced dynamic nuclear polarization (CIDNP) effects and from data on the products of the reaction between Et 3Al and CCl4 in the presence of Pd(acac)2. According to the results of qualitative analysis of the CIDNP effects, the reactions of the trialkylalanes and the cyclic organoaluminum compound with CCl4 in the presence of various metal complexes proceeded via similar mechanisms.
- Sadykov,Safina,Teregulov,Paramonov
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experimental part
p. 497 - 501
(2011/01/10)
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- Addition of tetrachloromethane to oct-1-ene initiated by amino alcohols
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The kinetics and mechanism of an addition of CCl4 to oct-1-ene initiated by amines, aromatic alcohols, and amino alcohols (structural analogs of ephedrin) were studied. The radical mechanism of the reaction was established by ESR using the technique of spin traps. Aromatic amino alcohols as initiators are more active than amines and aromatic alcohols of similar structure. They are more selective compared to the amines and aromatic alcohols and react with CCl4 already at room temperature to form predominantly benzaldehyde. The scheme of initiation by aromatic amino alcohols of the addition of CCl 4 to olefins was proposed on the basis of the experimental data.
- Tarkhanova,Gantman,Chizhov,Smirnov
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p. 1624 - 1630
(2007/10/03)
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- Oxidation of monohydric and dihydric alcohols with CCl4 catalyzed by molybdenum compounds
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Mo(CO)6 catalyzed oxidation of alcohols and diols with tetrachloromethane. Primary oxidation products in reaction of alcohols with CCl4 are alkyl hypochlorites, and final products depending on the structure of initial alcohol are aldehydes (as acetals), ketones, chloroketones, and esters.
- Khusnutdinov,Shchadneva,Burangulova,Muslimov,Dzhemilev
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p. 1615 - 1621
(2007/10/03)
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- Reactions in low temperature solid co-condensates and size effects
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The interaction of magnesium atoms, clusters and nanoparticles with different organic and inorganic substances were studied in low temperature solid cocondensates. A combination of matrix isolation techniques and preparative cryochemistry was applied to distinguish the activity of metal species of different sizes.
- Sergeev, Gleb B.
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- Chlorination of Adamantane and Its Derivatives by Carbon Tetrachloride in the Presence of Manganese-, Vanadium-, and Molybdenum-containing Catalysts
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The feasibility of catalytic chlorination of adamantane and its derivatives by carbon tetrachloride in the presence of manganese-, vanadium-, and molybdenum-containing catalysts activated by nitrile ligands or alcohols was established. The optimum molar ratios of catalyst components and reactants and the optimum reaction conditions for selective syntheses of mono-, di-, and trichlorosubstituted adamantane derivatives with high yields were found.
- Khusnutdinov,Shchadneva,Baiguzina,Lavrent'eva,Burangulova,Dzhemilev
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p. 126 - 133
(2007/10/03)
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- Methane to olefins
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The specification discloses a process for the production of olefins, including ethylene, propylene and butenes, from methane, the process comprising first, second and third reaction steps operated in tandem. In the first reaction step, hydrogen chloride, perchloroethylene and oxygen are reacted in the presence of a catalyst, using methane as a diluent, to yield hexachloroethane and water. In the second reaction step, the hexachoroethane from the first reaction step is reacted with methane to produce methyl chloride, hydrogen chloride and perchloroethylene. In the third reaction step, the methyl chloride from the second reaction step is reacted to give the desired olefins and hydrogen chloride. By recycling the perchloroethylene from the second reaction step and the hydrogen chloride from both the second and third reaction steps to the first reaction step, a balanced process is achieved that is self-sufficient in chlorine values.
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- Dynamic behaviour of chlorofluoroethanes at fluorinated chromia aerogels and fluorinated zinc(II) or magnesium(II) doped chromia aerogels
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The preparation and characterisation of two series of fluorinated chromia aerogel materials, lightly doped with zinc(II) or magnesium(II), are described. They behave as heterogeneous catalysts for transformations of 1,1,2-trichlorotrifluoroethane under HF
- Bozorgzadeh, Hamid,Kemnitz, Erhard,Nickkho-Amiry, Mahmood,Skapin, Toma?,Winfield, John M.
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- 1,1,1,3,3-pentachloropropane process purge stream concentration using a secondary refluxed evaporator and secondary product recovery
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A process for economically producing 1,1,1,3,3-pentachloropropane under conditions which preserve the activity of the catalyst. In a preferred embodiment, a two-stage distillation process is employed. In the two-stage process, the size of the equipment, temperature and vacuum are varied.
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Page/Page column 7
(2008/06/13)
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- Tetrachloroethylene oxide: hydrolytic products and reactions with phosphate and lysine.
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Tetrachloroethylene, or perchloroethylene (PCE), has considerable industrial use and is of toxicological interest because of a variety of effects. Most of the existing literature presents PCE oxide as a critical intermediate in the oxidative metabolism of PCE to Cl(3)CCO(2)H, oxalic acid, and products covalently bound to proteins, including trichloroacetyl derivatives of lysine. PCE oxide was synthesized by photochemical oxidation of PCE and characterized. Decomposition at neutral pH (t(1/2) = 7.9 min at 0 degrees C, 5.8 min at 23 degrees C, 2.6 min at 37 degrees C) yielded only trace ( approximately 1%) Cl(3)CCO(2)H; the major products identified were CO (73% yield) and CO(2) (63% yield). In phosphate buffer (0.10 M) a major product was identified as oxalyl phosphate. Oxalyl chloride also reacted to form CO and CO(2) in aqueous solution and to form oxalyl phosphate in neutral phosphate buffer. Oxalyl phosphate decomposed to oxalic acid (t(1/2) = 53 min at 37 degrees C) but did not react with lysine. Reaction of PCE oxide with free lysine yielded the oxalic acid amide derivatives of lysine plus lysine dimers in which cross-linking of the amino groups involved oxalo linkage. The reaction of PCE oxide with albumin yielded mainly N(6)-oxalolysine and some (5%) N(6)-trichloroacetyllysine. We propose a reaction pathway for PCE oxide based on our previous studies with trichloroethylene oxide, in which C-C bond scission is a major product of reaction in aqueous buffer and yields CO and CO(2). Oxalyl species are proposed as intermediates and prominent acylating species formed in the reactions of the epoxide. The formation of Cl(3)CCO(2)H in cytochrome P450 reactions is postulated to result from intramolecular migration within an enzyme intermediate.
- Yoshioka, Tadao,Krauser, Joel A,Guengerich, F Peter
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p. 1096 - 1105
(2007/10/03)
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- Liquid-phase hydrodechlorination of CCl4 with co-production of diethylcarbonate and acetal
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Liquid-phase hydrodechlorination of CCl4 over supported Pd or Pt catalysts in the presence of C2H5OH gave not only the selective synthesis of CHCl3, but also conversion of C2H5OH to diethyl
- Bae, Jong Wook,Lee, Jae Sung,Lee, Kyung Hee,Jang, Eun Joo
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p. 1020 - 1021
(2007/10/03)
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- Organochlorine formation in magnesium electrowinning cells
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The formation of organochlorines during the electrolytic production of magnesium was investigated using a laboratory-scale electrolytic cell having a graphite anode, a liquid aluminium alloy cathode, and a molten chloride electrolyte. The cell was operated at current densities ranging from 3000 to 10,000 A m-2 and at temperatures ranging from 660°C to 750°C. Organochlorines were adsorbed from the cell off-gases onto silica gel, extracted with hexane, and determined by gas chromatography. All compounds identified were fully chlorinated aliphatic and aromatic compounds, the major components being hexachlorobutadiene, hexachlorobenzene, hexachloroethylene, and octachlorostyrene. The total amount of organochlorines per tonne of magnesium produced decreased with electrolysis time and with current density and increased with operating temperature; it was also dependent on the type of graphite employed. The output of organochlorines Varied from 5 to 20 g t-1 of magnesium.
- Deutscher,Cathro
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p. 147 - 155
(2007/10/03)
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- Studies of photochemical reactions of 7,8-digermabicyclo[2.2.2]octadienes by steady-state and laser flash photolysis techniques
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The photochemistry of 1,4-diphenyl-2,3-benzo-7,7,8,8-tetraalkyl-7, 8-digermabicyclo[2.2.2]-octadienes in solution has been studied in detail by steady-state, nanosecond laser flash photolysis, and matrix isolation techniques. Photolysis of 7,8-digermabicy
- Mochida, Kunio,Kayamori, Takanari,Wakasa, Masanobu,Hayashi, Hisaharu,Egorov, Mikhail P.
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p. 3379 - 3386
(2008/10/08)
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- Formation of complex organochlorine species in water due to cavitation
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Sonication at 900 kHz was carried out on aqueous solutions of chloroform in the concentration range 25 to 500 mg/L. The formation of chlorinated hydrocarbons was detected by means of GC/MS analyses. For instance, carbon tetrachloride, chlorinated ethanes, and chlorinated ethenes were formed after 10 min of sonication. The greatest concentration of any product was 6 mg/L. Sonication of aqueous chloroform with phenol present produced chlorophenols, and with benzene present produced phenol, chlorobenzene and chlorophenols. These results are significant for the evaluation of sonication as a method of eliminating chlorinated organic compounds from water. They also have significance in supporting the notion that some complex organochlorines may be formed naturally in the environment. Some chloroform and methyl chloride are produced in nature and could react with other organic compounds to form more complex organochlorines through natural processes which have an action similar to cavitation, e.g. waterfalls and breaking waves.
- Kruus, Peeter,Beutel, Lise,Aranda, Rocio,Penchuk, Jaan,Otson, Rein
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p. 1811 - 1824
(2007/10/03)
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- Kinetics and mechanism of the enhanced reductive degradation of CCl4 by elemental iron in the presence of ultrasound
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Enhanced rates of sonolytic degradation of CCl4 in the presence of Fe0 are demonstrated. In Ar-saturated solutions, the first-order rate constant for CCl4 degradation is k(US) = 0.107 min-1, whereas in the presence of Ar and Fe0, the apparent first-order rate constant is found to depend on the total surface area of elemental iron in the following fashion: k(obs) = (k(US) + k(Fe)0A(Fe)0) min-1, where k(US) = 0.107 min-1, k(Fe)0 = 0.105 L m-2 min-1 and A(Fe)0) = reactive surface area of Fe0 in units of m2 L-1. In the coupled ultrasound and iron system, the contribution to the overall degradation rate by direct reaction with Fe0 results in an overall rate enhancement by a factor of 40. These enhancements are attributed (1) to the continuous cleaning and chemical activation of the Fe0 surface by the combined chemical and physical effects of acoustic cavitation and (2) to accelerated mass transport rates of reactants to the Fe0 surfaces. Additional kinetic enhancements are due to the production of H+ during the course of the reaction. Furthermore, the concentrations of the principal reaction intermediates, C2Cl6 and C2Cl4, are influenced substantially by the total available surface area of Fe0. Enhanced rates of sonolytic degradation of CCl4 in the presence of Fe0 are demonstrated. In Ar-saturated solutions, the first-order rate constant for CCl4 degradation is kUS = 0.107 min-1, whereas in the presence of Ar and Fe0, the apparent first-order rate constant is found to depend on the total surface area of elemental iron in the following fashion: kobs = (kUS+kFe0AFe0) min-1, where kUS = 0.107 min-1, kFe0 = 0.105 L m-2 min-1, and AFe0) = reactive surface area of Fe0 in units of m2 L-1. In the coupled ultrasound and iron system, the contribution to the overall degradation rate by direct reaction with Fe0 results in an overall rate enhancement by a factor of 40. These enhancements are attributed (1) to the continuous cleaning and chemical activation of the Fe0 surface by the combined chemical and physical effects of acoustic cavitation and (2) to accelerated mass transport rates of reactants to the Fe0 surfaces. Additional kinetic enhancements are due to the production of H+ during the course of the reaction. Furthermore, the concentrations of the principal reaction intermediates, C2Cl6 and C2Cl4, are influenced substantially by the total available surface area of Fe0.
- Hung, Hui-Ming,Hoffmann, Michael R.
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p. 3011 - 3016
(2007/10/03)
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- Novel photocatalytic mechanisms for CHCl3, CHBr3, and CCl3CO2 degradation and the fate of photogenerated trihalomethyl radicals on TiO2
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The photocatalytic degradation of CHCl3, CHBr3, CCl4, and CCl3CO2- is investigated in aqueous TiO2 suspensions. A common intermediate, the trihalomethyl radical, is involved in the degradation of each substrate except for CCl3CO2-, CHCl3 and CHBr3 are degraded into carbon monoxide and halide ions in the absence of dissolved oxygen. The anoxic degradation proceeds through a dihalocarbene intermediate, which is produced by sequential reactions of the haloform molecule with a valence band hole and a conduction band electron. Carbon dioxide and halide ion are formed as the primary products during CHCl3 degradation in the presence of oxygen. Under these conditions, the trihalomethyl radicals react rapidly with dioxygen. At pH > 11, degradation of the haloforms is enhanced dramatically. This enhancement is ascribed to photoenhanced hydrolysis. The secondary reactions of the trichloromethyl radical generated during CCl4 photolysis is strongly influenced by the nature of the electron donors. Both ·CCl3 and Cl- production increase substantially when 2-propanol is present as an electron donor. A new photocatalytic mechanism for CCl3CO2- degradation, which involves the formation of a dichlorocarbene intermediate, is proposed.
- Choi, Wonyong,Hoffmann, Michael R.
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- Supported complexes of cupric chloride with DMF as catalysts in the reaction of CCl4 with n-decane
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The complex of cupric chloride with DMF immobilized on the surface of silica gel exhibits high catalytic activity in the reaction of tetrachloromethane with n-decane. The fact that the reaction is inhibited by phenols and oxygen implies that it occurs by
- Golubeva,Nevskaya,Vorontsov,Abdrashitov
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p. 1741 - 1744
(2007/10/03)
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- The pyrolysis of CCl4 and C2Cl6 in the gas phase. Mechanistic modeling by thermodynamic and kinetic parameter estimation
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A detailed radical reaction mechanism is proposed to describe the thermal reactions of CCl4 and C2Cl6 in the gas phase quantitatively. A consistent set of activation energies and preexponential factors for all elementary reactions, in combination with enthalpies of formation and entropies for all species involved, is computer optimized to fit experimental pressure-rise curves and concentration profiles. For this purpose new experimental results on the pyrolysis of CCl4 are used, together with published kinetic data on the pyrolysis of C2Cl6 (in the absence and in the presence of Cl2).
- Huybrechts,Narmon,Van Mele
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- Kinetics and mechanism of the sonolytic degradation of CCL4: Intermediates and byproducts
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The sonolytic degradation of aqueous carbon tetrachloride is investigated at a sound frequency of 20 kHz and 135 W (112.5 W cm-2) of power. The observed first-order degradation rate constant in an Ar-saturated solution is 3.3 x 10-3 s-1 when the initial CCh concentration, [CCl4](i), is 1.95 x 10-4 mol L-1 and increases slightly to 3.9 x 10-3 s-1 when [CCl4](i) = 1.95 x 10-5 mol L-1. Low concentrations (10-8-10-7 mol L-1) of the organic byproducts, hexachloroethane and tetrachloroethylene, are detected, as well as the inorganic products chloride ion and hypochlorous acid. The chlorine mass balance after sonolysis is determined to be >70%. The reactive intermediate, dichlorocarbene, is identified and quantified by means of trapping with 2,3-dimethyl-2-butene. The presence of ozone in the sonicated solution does not significantly effect the rate of degradation of carbon tetrachloride; however, O3 inhibits the accumulation of hexachloroethane and tetrachloroethylene. Ultrasonic irradiation of an aqueous mixture of p-nitrophenol (p-NP) and carbon tetrachloride results in the acceleration of the sonochemical degradation of p-NP. The sonolytic rate of degradation of p-NP appears to be enhanced by the presence of hypochlorous acid, which results from the sonolysis of CCl4.
- Hua, Inez,Hoffmann, Michael R.
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p. 864 - 871
(2007/10/03)
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- Radical versus "oxenoid" oxygen insertion mechanism in the oxidation of alkanes and alcohols by aromatic peracids. New synthetic developments
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Evidences concerning a novel free-radical mechanism for the oxidation of alkanes by aromatic peracids are reported. The mechanism involves hydrogen abstraction from the OH group of peracids by an aroyloxyl radical; the acylperoxyl radical thus generated is responsible for the selective oxidation. The reaction is affected by the presence of oxygen and it is inhibited by TEMPO and by solvents forming hydrogen bonds with peracids. A more simple and effective synthetic procedure has been developed, on the basis of the autoxidation of aliphatic and aromatic aldehydes in the presence of alkanes. It is also shown that the previously reported inertness of alcohols toward peracids must be ascribed to solvent effects, due to the formation of hydrogen bonds; in suitable solvents alcohol oxidation smoothly occurs.
- Bravo, Anna,Bjorsvik, Hans-Rene,Fontana, Francesca,Minisci, Francesco,Serri, Anna
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p. 9409 - 9416
(2007/10/03)
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- Reductive alkylation of electronegatively-substituted alkenes by alkylmercury halides
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Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCH2CH(EWG).] that in some cases react with RHgX to form RCH2CH(HgX)(EWG), e.g., EWG = (EtO)2PO or PhSO2. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCl/KI in Me2SO leads to the adduct mercurial via reaction of the adduct radicals with RHgI2-. The reactions of tertiary-enolyl adduct radicals are inefficient with RHgX/KI, and disproportionation of the adduct radicals is the major reaction pathway. For secondary- or tertiary-adduct radicals the reductive alkylation products are formed in excellent yield by reaction with RHgCl and silyl hydrides in Me2SO solution in a process postulated to involve RHgH as an intermediate. The relative reactivities of a number of α,β-unsaturated systems toward t-Bu. have been measured by competitive techniques. The results demonstrate a high reactivity of s-cis enones relative to the s-trans conformers.
- Russell, Glen A.,Shi, Bing Zhi,Jiang, Wan,Hu, Shuiesheng,Kim, Byeong H.,Baik, Woonphil
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p. 3952 - 3962
(2007/10/02)
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- Hydrodechlorination of Tetrachloromethane over Supported Pt Catalysts
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In the selective hydrodechlorination of tetrachloromethane to chloroform, long catalytic life as well as high selectivity to chloroform is achieved over a platinum catalyst supported on MgO.
- Kim, Sang Y.,Choi, Hyun C.,Yanga, O B.,Lee, Kyung H.,Lee, Jae S.,Kim, Young G.
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p. 2169 - 2170
(2007/10/02)
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- Catalytic Liquid-phase Fluorination of Tetrachlorethene (PCE) with Titanium Antimony Mixed Halides
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A new catalyst consisting of a TiCl4-SbCl5 mixture with a molar composition Sb : Ti = 4 : 1 makes possible the fluorination of tetrachlorethene with liquid HF at 90 deg C.
- Batiot, Catherine,Brunet, Sylvette,Barrault, Joel,Blanchard, Michel
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p. 867 - 868
(2007/10/02)
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- THERMALLY-CONTROLLED FORMATION OF CRYSTALLINE HEXACHLOROBENZENE, HEXACHLOROETHANE, AND ANHYDROUS CHROMIUM CHLORIDE
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The high-temperature preparation of purple crystalline anhydrous chromium chloride (CrCl3) by passing CCl4 vapors over green Cr2O3 powder in an inert atmosphere is an instructive experiment in the inorganic chemistry laboratory.A systematic investigation of this synthesis (using a carefully calibrated tube furnace, X-ray powder diffraction, infrared spectroscopy, and gas chromatography) revealed that the products formed as a consequence of the pyrolysis of CCl4 are sensitive to the reaction temperature.When Cr2O3 is present, the formation of CrCl3 dominates at temperatures between 600 deg C and 800 deg C; at temperatures above 900 deg C, C6Cl6 forms preferentially (presumably from the linking of the C-Cl free radicals produced by the pyrolysis) as the unreacted metal oxide is sintered to form eskolaite.In the absence of Cr2O3, the pyrolysis products are crystalline hexachloroethane (C2Cl6) at 600 deg C and needle-shaped crystals of hexachlorobenzene at temperatures above 900 deg C.
- Rudman, Reuben,Stevenson, Cynthia
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p. 105 - 112
(2007/10/02)
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- Thermolysis of phenoxyaluminum compounds and formation of PCDD/F and their precursors
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Within the study of the formation of chlorinated dioxins and dibenzofurans and their precursors the thermolysis of hexachloroethane over the aluminum melt was investigated. "De novo" synthesis of precursors of PCDD/F was studied in the model system AlCl3/elemental carbon. Totally chlorinated heterocyclic compounds have been detected parallel with the formation of organochlorine compounds. The possibility of inserting oxygen to aluminum organyls was presented. In order to gain more detailed knowledge of the catalytic behaviour of fly ash the chemistry of thermolysis of phenoxy- and chlorophenoxy aluminum compounds at 300°C with the presence and absence of Al2O3 was investigated. Reagent compounds and products of thermolysis were followed by mass spectrometry.
- Voncina,Medved,Zerjal
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p. 2029 - 2038
(2007/10/03)
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- Catalytic carbon-halogen bond cleavage chemistry by redox-active polyoxometalates
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The use of redox-active polyoxotungstate complexes to effect the cleavage of carbon-halogen bonds (C-X, X = Cl or Br) by three distinct modes is demonstrated for the first time. The first mode involves direct thermal reaction of halocarbon substrates with H2W10O324- or α-HPW12O403-. The rate law for CCl4 dehalogenation is V = k(H2W10O324-)(CCl4) and k(H2W10O324-)/k(α-HPW 12O403-) = 2.8. Several lines of evidence collectively establish that carbon-halogen bond cleavage likely involves dissociation electron transfer for the mode 1 reactions, although halogen atom abstraction (atom transfer) cannot be ruled out. The evidence includes comparisons of kinetic profiles for dehalogenation rate versus halocarbon substrate structure, relative reactivities of substrates (polyhalogenated more reactive (>) than monohalogenated compounds; tertiary > secondary > primary halides; bromides > chlorides), and other product distribution data including one "radical clock" reaction, in addition to the rate law. Interestingly one carbocation derived product, N-tert-butylacetamide, is generated in the debromination of tert-butyl bromide in acetonitrile. The second and third modes of dehalogenation involve extensions of previously reported polyoxometalate photoredox processes, and both modes are catalytic extensions of existing effective stoichiometric dehalogenation processes. The second mode proceeds by a complex rate law and involves photocatalytic transformation of organic halide (halocarbons) into inorganic halide (HX) coupled with the oxidation of sacrificial organic reductants (secondary alcohols or tertiary amides). The second mode essentially defines a method to catalytically generate reducing radicals under mild conditions; the radicals are the principal dehalogenating species. The third mode of dehalogenation is similar to the second mode but run in the presence of O2. Here the reduced polyoxotungstates reduce O2 to superoxide which then dehalogenates substrate. The third mode effects catalytic dehalogenation of a wide range of halocarbons.
- Sattari, Daryush,Hill, Craig L.
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p. 4649 - 4657
(2007/10/02)
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- Effect of the solvent on the diffusional mobility and on the recombination rate constant of trichloromethyl radicals in solution
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The translational diffusion coefficients (D) of CCl3* radicals in liquid solutions differing in the type of solvent and in viscosity have been determined at 298 - 343 K by photochemical space intermittency.We show that at high concentrations of trichloro bromomethane the observed D values are significantly higher than those expected theoretically.This is attributed to the fast reaction Cl3C* + Br-CCl3 --> Cl3C-Br + *CCl3, which was detected experimentally by the radiactive indicator method.The process is formally described by the laws of molecular diffusion.Absolute value s of its rate constant have been calculated.The effect of the concentration of trichlorobromomethane on the observed rate constant of the recombination of CCl3* radicals has been established.
- Kochetov, I. N.,Tarasova, N. P.
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p. 1271 - 1274
(2007/10/02)
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- KINETICS OF SOME CHLOROMETHANES: SONOLYSIS IN AQUEOUS MEDIA
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The kinetics of Cl2 generation in mixed CH2Cl2/H2O, CHCl3/H2O, and CCl4/H2O systems under sonolysis at 25 deg C was studied. Both the reaction order and the dependence of the rate constant upon the incident ultrasonic power are consistent with a reaction mechanism involving H., OH. and chloromethyl radicals.
- Popa, Niculae,Ionescu, Savu Gheorghe
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p. 697 - 702
(2007/10/03)
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- The mechanism of the addition of haloalkanes to alkenes in the presence of and
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Kinetic and other studies have demonstrated that the addition of haloalkanes to alkenes in the presence of either or has a mechanism very similar to that observed in the presence of .The previous report of enhanced catalytic activity for the two hydrides has not been confirmed.
- Davis, Reg,Furze, John D.,Cole-Hamilton, David J.,Pogorzelec, Peter
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p. 191 - 196
(2007/10/02)
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- Addition of tetrachloromethane to trifluoroethene catalyzed by copper complexes
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The addition of tetrachloromethane to trifluoroethene catalyzed by copper complexes gives 1:1 adducts in up to 97percent yield under mild reaction conditions.The catalytic activity and the regioselectivity of copper, ruthenium and palladium complexes and dibenzoyl peroxide have been compared.Differeneces in regioselectivity indicate that the copper-coordinated trichloromethyl radical is involved in copper-assisted addition reactions, whilst free-radical species in an uncomplexed form play a role in other cases.
- Kotora, M.,Hajek, M.
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- Photochemical Reactions of Vinyl-, Styryl- and Benzyl-Substituted Digermanes
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Photochemical reactions of vinyl-, styryl- and benzyl-substituted digermanes by chemical trapping experiments.Photolysis of vinylpentamethyldigermane afforded 1-trimethyl-2-(pentamethyldigermyl)ethane as a major product, and styrylpentamethyldigermanes gave mainly styryltrimethylgermane.On the other hand, photolysis of benzyl-substituted digermanes (benzylpentamethyldigermane and 1,2-dibenzyltetramethyldigermane) gave hydrogermanes and hydrodigermanes as main products, respectively.These products were derived from germyl radicals generated by photoinduced homolysis of the germanium-germanium bond.In carbon tetra chloride (CCl4), these germyl radicals were converted to the corresponding chlorogermanes by abstraction of a chlorine atom.Germylene species were also to be evolved from such photolyses.
- Mochida, Kunio,Kikkawa, Haruhiko,Nakadaira, Yasuhiro
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p. 2772 - 2777
(2007/10/02)
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- MECHANISMS OF FREE-RADICAL REACTIONS. NATURE OF CHAIN DEVELOPMENT IN THE FRRE-RADICAL HALOGENATION OF ALKYL AROMATIC HYDROCARBONS BY TRICHLOROMETHANESULFONYL CHLORIDE AND BROMOTRICHLOROMETHANE
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Comparison of the selectivity parameters (the relative rate constants, reaction constant ρ, and kinetic isotope effect) for the chlorination of alkyl compounds by trichloromethanesulfonyl chloride with the known selectivity parameters of the trichloromethyl radical, determined by the labeled atom method, showed that the abstraction of the hydrogen atom from the substrate in the free-radical chlorination of hydrocarbons by trichloromethanesulfonyl chloride is realized both by the trichloromethyl and by the trichloromethanesulfonyl radical.In a similar way it was shown that the bromination of hydrocarbons by bromotrichloromethane takes place with participation of the trichloromethyl radicals and bromine atoms.
- Dneprovskii, A. S.,Iz'yurov, A. L.,Boyarskii, V. P.,Eliseenkov, E. V.
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p. 701 - 704
(2007/10/02)
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