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Transmission Fourier transform infrared spectroscopy has been used to identify gas-phase and surface-bound products and intermediates formed during the gas-phase photooxidation of trichloroethylene (TCE) on TiO2 and ZnO. Several factors are found to influence the gas-phase product distribution for this reaction. On clean TiO2 and ZnO surfaces and at high TCE and O2 pressures, gas-phase CO, CO2, COCl2, CCl2HCOCl, CHCl3, C2HCl5, and HCl are produced, whereas at low TCE and O2 pressures, TCE is converted to gas-phase CO and CO2 only. In addition to TCE and O2 pressure, the product distribution of the photooxidation of TCE is strongly dependent upon the coverage of adsorbed species on the surface of the photocatalyst. It is shown here that the complete oxidation of adsorbed TCE can occur on clean photocatalytic surfaces whereas only partial oxidation of adsorbed TCE occurs on adsorbate-covered surfaces. The role of adsorbed surface products in TCE photooxidation is discussed.

The kinetics of the reaction of the CH2Br, CHBrCl or CCl3 radicals, R, with HBr have been investigated separately in a heatable tubular reactor coupled to a photoionization mass spectrometer. The CH2Br (or CHBrCl or CCl3) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH2Br2 (or CHBr2Cl or CBrCl3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student's t values, units in cm3 molecule-1 s-1): k(CH2Br + HBr) = (7.5 ± 0.9) × 10-13 exp[- (2.53 ± 0.13) kJ mol-1/RT], k(CHBrCl + HBr) = (4.9 ± 1.1) × 10-13 exp[-(8.2 ± 0.3) kJ mol-1/RT] and k(CCl3 + HBr) -15 at 787 K. The kinetics of the reverse reactions, Br + R′H → HBr + R′ (R′ = CH2Br or CHBrCl), were taken from the literature and also calculated by ab initio methods at the MP2(fc)/6-31G(d,p)//MP2(fc)/6-31G(d,p) level of theory in conjunction with the thermodynamic transition state theory to calculate the entropy and the enthalpy of formation values of the radicals studied. The thermodynamic values were obtained at 298 K using a second-law method. The results for entropy values are as follows (units in J K-1 mol-1): 263 ± 7 (CH2Br) and 294 ± 6 (CHBrCl). The results for enthalpy of formation values at 298 K are (in kJ mol-1): 171.1 ± 2.7 (CH2Br) and 143 ± 6 (CHBrCl). The C-H bond strength of analogous halomethanes are (in kJ mol-1): 427.2 ± 2.4 (CH3Br) and 406.0 ± 2.4 (CH2BrCl). Thermodynamic properties of the CH2Br radical were calculated by statistical thermodynamic methods over the temperature range 100-1500 K.

The kinetics were studied with due consideration taken of the radial variation in light intensity across the reactor and with the proper selection of kinetic equations, including the recombination of dichloromethyl radicals as the dominant termination step. The dependence of the absorbed radiant energy on the chlorine concentration was well simulated by the use of the radial-light and line-source model. The predominance of the observed production rate of hydrogen chloride over that of chloroform was also reproduced well by the appropriately selected kinetic expressions, without any use of the long-chain approximation. This work is pertinent to photochemical reactor design.

The behaviour of the haloketones (HKs) 1,1-Dichloropropanone (1,1-DCP), 1,1,1-Trichloropropanone (1,1,1-TCP) and 1,3-Dichloropropanone (1,3-DCP) in ultrapure water solutions and in fortified drinking water samples was invest/gated. Their concentrations were determined at regular time intervals by the use of a gas chromatography-electron capture detector (GC-ECD) method. Two different temperatures were studied. The results have shown that HKs decompose both in ultrapure water solutions and in drinking water samples. The decomposition rates are higher in the drinking water samples, especially at higher temperature. 1,1,1-TCP is the compound which decomposes fastest followed by 1,3-DCP and 1,1-DCP. Chloroform was formed both in the ultrapure water solutions and in the drinking water samples, probably due to the decomposition of 1,1,1-TCP. In the drinking water samples, formation of chloral hydrate was also observed.

In this study, chlorine dioxide (ClO2) was used as an alternative disinfectant with vanillic acid, p-hydroxybenzoic acid, and humic acid as the organic precursors in a natural aquatic environment. The primary disinfection by-products (DBPs) formed were trihalomethanes (THMs) and haloacetic acids (HAAs). Under neutral conditions (pH = 7) for vanillic acid, more total haloacetic acids (THAAs) than total trihalomethanes (TTHMs) were found, with a substantial increase during the later stages of the reaction. In the case of p-hydroxybenzoic acid, the amount of THAAs produced was minimal. Raising the concentration of ClO2 was not favorable for the control of THAAs in low concentrations of vanillic acid. ClO2 could reduce the total amount of TTHMs and THAAs for higher concentration of vanillic acid. It was found that the humic acid treatment dosage was not significant. Under alkaline conditions (pH = 9), the control of TTHMs and THAAs for the treatment of vanillic acid was better and more economical, however, an appreciable amount of inorganic by-products were observed. Under the same alkaline condition, the control of THAA for the treatment of p-hydroxybenzoic acid was not beneficial and for the treatment of humic acid was not significant. (C) 2000 Elsevier Science Ltd.

Visible-light-driven TiO2 photocatalysts doped with nitrogen have been prepared as powders and thin films in a cylindrical tubular furnace under a stream of ammonia gas. The photocatalysts thus obtained were found to have a band-gap energy of 2.95 eV. Electron spin resonance (ESR) under irradiation with visible light (λ ≥ 430 nm) afforded the increase in intensity in the visible-light region. The concentration of trapped holes was about fourfold higher than that of trapped electrons. Nitrogendoped TiO 2 has been used to investigate mechanistically the photocatalytic oxidation of trichloroethylene (TCE) under irradiation with visible light (λ ≥ 420 nm). Cl and O radicals, which contribute significantly to the generation of dichloroacetyl chloride (DCAC) in the photocatalytic oxidation of TCE under UV irradiation, were found to be deactivated under irradiation with visible light. As the main by-product. only phosgene was detected in the photocatalytic oxidation of TCE under irradiation with visible light. Thus, the reaction mechanism of TCE photooxidation under irradiation with visible light clearly differs markedly from that under UV irradiation. Based on the results of the present study, we propose a new reaction mechanism and adsorbed species for the photocatalytic oxidation of TCE under irradiation with visible light. The energy band for TiO2 by doping with nitrogen may involve an isolated band above the valence band.

Effect of isoflurane on the dechlorination of carbon tetrachloride to chloroform was investigated in the guinea-pip liver microsomes. Under anaerobic conditions, chloroform is produced from carbon tetrachloride through the microsomes in the presence of NADPH, and such production of chloroform was increased by the addition of isoflurane. The K(m) for the production of chloroform from carbon tetrachloride was decreased to 86% by isoflurane compared with the control; however the maximum velocity of chloroform production was also decreased to 50%. The formation of the 445 nm band in the mixture of reduced cytochrome P-450 and carbon tetrachloride, and cytochrome P-450 reduction by NADPH were both accelerated by isoflurane, without alteration of NADPH-cytochrome c reductase activity. These results indicate that trichloromethyl radical, an intermediate product of carbon tetrachloride, easily combines to the haeme part of cytochrome P-450, whereas the protein part combines to isoflurane after being reduced by NADPH, which results in acceleration of carbon tetrachloride dechlorination under a lower concentration of carbon tetrachloride. These results may have implications for other drugs that are administered during isoflurane anaesthesia.

The mechanisms involved in reductive dechlorination of carbon tetrachloride (CT) and trichloroethylene (TCE) at iron surfaces were studied to determine if their reaction rates were limited by rates of electron transfer. Chronoamperometry and chronopotentiometry analyses were used to determine the kinetics of CT and TCE reduction by a rotating disk electrode in solutions of constant halocarbon concentration. Rate constants for CT and TCE dechlorination were measured as a function of the electrode potential over a temperature range from 2 to 42 °C. Changes in dechlorination rate constants with electrode potential were used to determine the apparent electron-transfer coefficients at each temperature. The transfer coefficient for CT dechlorination was 0.22 ± 0.02 and was independent of temperature. The temperature independence of the CT transfer coefficient is consistent with a rate-limiting mechanism involving an outer-sphere electron-transfer step. Conversely, the transfer coefficient for TCE was temperature dependent and ranged from 0.06 ± 0.01 at 2 °C to 0.21 ± 0.02 at 42 °C. The temperature-dependent TCE transfer coefficient indicated that its reduction rate was limited by chemical dependent factors and not exclusively by the rate of electron transfer. In accord with a rate-limiting mechanism involving an electron-transfer step, the apparent activation energy (Ea) for CT reduction decreased with decreasing electrode potential and ranged from 33.0 ± 1.6 to 47.8 ± 2.0 kJ/mol. In contrast, the E, for TCE reduction did not decline with decreasing electrode potential and ranged from 29.4 ± 3.4 to 40.3 ± 3.9. The absence of a potential dependence for the TCE Ea supports the conclusion that its reaction rate was not limited by an electron-transfer step. The small potential dependence of TCE reaction rates can be explained by a reaction mechanism in which TCE reacts with atomic hydrogen produced from reduction of water.

Thirty organic compounds were selected to investigate their chloroform formation characteristics during chlorination with sodium hypochlorite at pH-values 7.0 and 8.0. These experiments were conducted under conditions similar to those applied on the chlorination of raw water. The results indicated that the chloroform concentrations occurred by the all tested compounds was in the ppm range. The maximum levels of chloroform (11-13 mg/l) were determined during the reaction of resorcinol and phloroglucinol at pH-value 8.0.

Effects of the anesthetics isoflurane, enflurane, halothane and sevoflurane on the dechlorination of carbon tetrachloride to produce chloroform were investigated using guinea pig liver microsomes. Under anaerobic conditions, chloroform is produced from carbon tetrachloride by the microsomes in the presence of NADPH, and chloroform production from 86 μM carbon tetrachloride was enhanced to 146%, 133%, 123% and 115% by the addition of isoflurane, enflurane, halothane and sevoflurane, respectively. The half-life of oxidized cytochrome P450 which remained during the reduction by the addition of NADPH was shortened to 51%, 54%, 60% and 80% by isoflurane, enflurane, halothane and sevoflurane, respectively, without alteration of NADPH-cytochrome c reductase activity. These anesthetics hastened the onset of the 445 nm absorption band formation which was shown by microsomes with carbon tetrachloride in the presence of NADPH under anaerobic conditions. These results indicate that the anesthetics isoflurane, enflurane, sevoflurane and halothane stimulate the reduction of cytochrome P450 results in the acceleration of the carbon tetrachloride dechlorination. These results may have implications for other type II drugs that are administered during anesthesia.

The rate constant of the reaction between CCl2 radicals and HCl was experimentally determined. The CCl2 radicals were obtained by infrared multiphoton dissociation of CDCl3. The time dependence of the CCl2 radic

CCl4 (CT) is one of the most frequently encountered chlorinated solvent pollutants in groundwater. Contributions of biotic (cell-mediated) and abiotic (mineral-mediated) reactions CT transformation were investigated in a model iron-reducing system that utilized hydrous ferric oxide (HFO) as the electron acceptor, acetate as the substrate, and Geobacter metallireducens as a representative dissimilative iron-reducing bacteria. The mineral-mediated (abiotic) reaction was estimated to be 60-260-fold faster than the biotic reaction throughout the incubation period. A second member of the dissimilative iron-reducing bacteria, G. metallireducens, could biotically transform CT. However, in the presence of HFO, G. metallireducens drove CT transformation primarily through the formation of reactive mineral surfaces. This did not diminish the role that DIRB play even though it suggested that biologically mineral surfaces may be the principal agents of reductive transformation in iron-reducing environments. The results indicated that an alternative approach to stimulate reductive transformation of pollutants in iron-reducing environments might be to improve the formation of reactive biogenic minerals in situ. Other FeII species have been identified in iron-reducing environments that are also reactive with chlorinated solvents including the ferrous sulfides, green rusts, and sorbed FeII. It could also be possible to couple microbial iron reduction to reactive barrier design to exploit the ability of such bacteria to reactivate passivated metal surfaces.

The feasibility of electrolytic removal of tetrachloromethane from industrial effluents has been investigated. A new method based on the electrochemical reductive dechlorination of CCl4 yielding chloroform is described. The main goal was not only to remove CCl4 but also to utilize the process for obtaining chloroform, which can be industrially reused. GC-MS analysis of the electrolysed samples showed that chloroform is the only product. Voltammetric experiments were made in order to select experimental conditions of the electrolysis. Using energetic and economic criteria, ethanol-water (1:4) and LiCl were found to be the optimum solvent and supporting electrolyte tested. No great differences were found while working at different pH values. Chronoamperometric and voltammetric experiments with convolution analysis showed low kf0 and α values for the reaction. A new differential pulse voltammetric peak deconvolution method was developed for an easier and faster analysis of the electrolysis products. Electrolysis experiments were carried out using both a bulk reactor and a through-flow cell. Thus, three different kinds of galvanostatic electrolyses were carried out. Under all conditions, CCl4 conversions ranging from 60 to 75% and good current efficiencies were obtained.

The base-catalyzed oxidative cleavage of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethanol (Dicofol) results in the formation of chloroform and 4,4'-dichlorobenzophenone.The reaction was studied in the presence of hexadecyltrimethylammonium bromide (CTAB) and hexadecyldimethyl(2-hydroxyethyl)ammonium bromide (CHEDAB), and catalytic factors of 200- and 345-fold, respectively, were obtained.The experimental results are rationalized in terms of an increase of the concentration of the reagents in the micellar phase.Sodium dodecyl sulfate (NaLS) inhibits the reaction, and dodecylcarnitine chloride (LCC) essentially does not alter the rate.The catalysis by cationic surfactants (CTAB, CHEDAB) is inhibited by added salts.The effectiveness of the salts in decreasing the rate constant is NaCl (excit.) = 27.7 kcal/mol, ΔG(excit.) = 19.8 kcal/mol, ΔS(excit.) = 25.9 eu) and for 1.0E-1 M CTAB (ΔH(excit.) = 26.7 kcal/mol, ΔG(excit.) = 20.8 kcal/mol, ΔS(excit.) = 19.6 eu) indicate that the rate decrease observed at high surfactant concentration is due to an entropic contribution to the free-energy term.

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The possibility of formation of halomethanes upon the photostimulated reaction of halogen-containing minerals with methane was shown. The dynamics of accumulation of chloromethane, dichloromethane, and chloroform in model systems CH4-NaCl, CH4-sylvinite, and CH4-halite was studied experimentally. The kinetic parameters for the formation of methyl chloride were determined.

Reductive dehalogenation, mediated by nonspecific biomimetic Co macrocycles, was studied in aqueous systems using carbon tetrachloride as a model compound. Two water-soluble macrocycles, cobalt tetrakis(N-methyl-4- pyridiniumyl)porphyrin (CoTMPyP) cation and cobalt tetrasulfophthalocyanine (CoPcTs) anion, were used as homogeneous and mineral-supported catalysts. The supported catalysts were prepared by exchanging CoTMPyP on the hectorite, fluorohectorite, and amorphous silica surface and by exchanging CoPcTs on the layered double hydroxide surface. Supported macrocycles were catalytically active in the dechlorination of CCl4 and the initial reaction rates followed Michaelis-Menten kinetics. The value of V(max) was correlated to the previously reported orientation of macrocycles in the interlayers and to the accessibility and electronic state of the metal center, following the order: CoTMPyP-silica > CoPcTs-layered double hydroxide > CoT-MPyP-fluorohectorite > CoTMPyP-hectorite. In both heterogeneous and homogeneous systems, volatile reaction products accounted for less than 30% of CCl4 degraded. In short- term experiments (2 h), homogeneous CoTMPyP was more active than heterogeneous catalysts, while homogeneous CoPcTs was deactivated due to aggregation, and degraded less CCl4 than supported CoPcTs. In long-term experiments (3 days), where large CCl4/macrocycle ratios were used, silica- supported CoTMPyP was more active than homogeneous CoTMPyP, suggesting that adsorption stabilized the catalyst.

Aliphatic chlorinated hydrocarbons, including CCl4, are widespread groundwater contaminants. Mechanisms and product formation of CCl4 reduction by Fe(II) sorbed to goethite, which may lead to completely dehalogenated products or to form chloroform, a toxic product that is fairly persistent under anoxic conditions, were studied. A simultaneous transfer of two electrons and cleavage of two C-Cl bonds of CCl4 would completely circumvent chloroform production. Product formation pathways did not primarily depend on the competition between an initial one- and two-electron transfer, but on the presence of different radical scavengers and the properties of the mineral surface with respect to stabilization of reaction intermediates. Specific adsorption of major anions or pH effects could modify the capability of the goethite surface to stabilize short-lived radical intermediates.

Catalytic hydrodechlorination of carbon tetrachloride (CCl4) is an effective measure to remove CCl4due to its pollutant character. The dechlorination of CCl4to dichloromethane (CH2Cl2) and chloroform (CHCl3) with a molar ratio of 3:2 was catalyzed by carbon-supported silver (Ag/C) catalyst in methanol solution. It was proposed from the catalytic results and characterization (X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy) data that, the chloride ion is abstracted from adsorbed CCl4by Ag to form CCl3and CCl2radicals and silver chloride (AgCl), and meanwhile the dehydrogenation of methanol over Ag domains intrigues initial active Ag-H species and formaldehyde (HCHO): then the CCl3and CCl2radicals are combined with Ag-H to generate reaction products (CHCl3, and CH2Cl2) and Ag, and the dehydrogenated product HCHO facilitates the regeneration of formed AgCl to Ag with formation of carbon monoxide and hydrogen chloride. The catalyst can be recovered and recycled, and there was no significant decrease in catalytic activity and selectivity after 4threcycling. Copyright

The objectives of this research work was to evaluate the reduction of THM precursors by cationic p-DADMAC and determine the correlations between the chlorine demand and trihalomethane formation in the presence of electrolyte solutions and ambient light. The chlorine demand was found to be significantly reduced provided that the H2SO4 electrolyte was fed to the sample solutions. The amount of CHCl3 formation was also decreased when the Na2SO4 electrolyte was introduced in spite of the levels of light intensity. The p-DADMAC can not only effectively remove the turbidity but also reduce the formation of CHCl3. The optimum dosage of p-DADMAC for reducing the turbidity, TOC and CHCl3 in the humic acid and source water samples was determined and depended upon the nature of organics. The objectives of this research work was to evaluate the reduction of THM precursors by cationic p-DADMAC and determine the correlations between the chlorine demand and trihalomethane formation in the presence of electrolyte solutions and ambient light. The chlorine demand was found to be significantly reduced provided that the H2SO4 electrolyte was fed to the sample solutions. The amount of CHCl3 formation was also decreased when the Na2SO4 electrolyte was introduced in spite of the levels of light intensity. The p-DADMAC can not only effectively remove the turbidity but also reduce the formation of CHCl3. The optimum dosage of p-DADMAC for reducing the turbidity, TOC and CHCl3 in the humic acid and source water samples was determined and depended upon the nature of organics.

The kinetics and mechanism of the reductive dehalogenation of CCl4 to chloroform were studied in the presence of aqueous acetone and 2-propanol, which was added as a hydrogen donor. The rate of reduction was very fast, stoichiometrically converted 3 mM CCl4 to chloroform in ~ 2 min. The zero-order reaction occurred at 2.7 x 10 -6 M/sec rate under typical conditions (0.69 M acetone, 5.7 M 2-propanol, 3 mM CCl4) using a 75 W Xe lamp. The mechanism was first order in CCl4 near the end of the reaction. The zero-order reaction rate increased with acetone, 2-propanol, and with absorbed light intensity. Other combinations of carbonyls, alcohols, and halogenated organics such as methyl ethyl ketone, methanol, ethanol, 1-propanol, and 1-butanol are also effective in dehalogenation via this process. Relative rates of dehydrogenation for a series of chlorinated methanes and ethanes such as trichloroethylene and perchloroethylene are presented.

The rate constants, k, for the decomposition of ammonium trichloroacetate in acetonitrile were determined at 298 K where B is an N-base.The first-order decarboxylation of trichloroacetic acid in the presence of N-bases is strongly deopendent upon proton transfer in complexes.Discussion of the rate constants, k, obtained shows 3 types of complexes in the proton-transfer mechanism, i.e. a symmetrically positioned proton, and without proton transfer for 2 cases: .The sigmoidal curve of rate constants, -log k, plotted against (pKa)AN describes the location of the proton in the hydrogen bridge.The behaviour of (CCl3COOHR)(1-) complexes has many similarities to the molecular complexes, CCl3COOHB, discussed above.Implications of these results for carboxylate additives in overbased lubricating oils are discussed.

Integral polarization of chloroform, methylene dichloride, and pentachloroethane was observed in the 1H NMR spectra during the exothermal reaction of a 1 M solution of Bui2AlH in 1,4-dioxane with CCl4. CIDNP was shown to appear in the diffusion radical pair of the hydrogen atom and trichloromethyl radical.

Previous experiments in our laboratory have demonstrated that the rate and extent of carbon tetrachloride (CT) and chloroform (CF) dechlorination were enhanced when a methanogenic enrichment culture and iron (Fe0) were incubated together. Batch experiments with three pure cultures of methanogens, Methanosarcina barkeri, Methanosarcina thermophila, and Methanosaeta concillii were performed to determine how this enhanced transformation occurred. When hydrogen (H2) was added as an electron donor, degradation of CT for all organisms and CF for M. thermophila was more rapid. H2 was produced from the oxidation of iron, which therefore served as an H2 source for the organisms, enhancing the transformation of CT and CF. Experiments with M. thermophila and M. concillii, which could not grow on H2-CO2 under the conditions tested, showed that H2 could serve as an electron donor for dechlorination of CT and CF with these organisms as well. Experiments with supernatants from M. thermophila grown with and without iron indicated the presence of an excreted biomolecule active in the enhanced transformation of CT and CF. Previous experiments in our laboratory have demonstrated that the rate and extent of carbon tetrachloride (CT) and chloroform (CF) dechlorination were enhanced when a methanogenic enrichment culture and iron (Fe0) were incubated together. Batch experiments with three pure cultures of methanogens, Methanosarcina barkeri, Methanosarcina thermophila, and Methanosaeta concillii were performed to determine how this enhanced transformation occurred. When hydrogen (H2) was added as an electron donor, degradation of CT for all organisms and CF for M. thermophila was more rapid. H2 was produced from the oxidation of iron, which therefore served as an H2 source for the organisms, enhancing the transformation of CT and CF. Experiments with M. thermophila and M. concillii, which could not grow on H2-CO2 under the conditions tested, showed that H2 could serve as an electron donor for dechlorination of CT and CF with these organisms as well. Experiments with supernatants from M. thermophila grown with and without iron indicated the presence of an excreted biomolecule active in the enhanced transformation of CT and CF.

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Carbon tetrachloride (CT) was dechlorinated to chloroform (CF) under anoxic conditions by Fe(II) which was sorbed to the surface of goethite (α-FeOOH). There was no reaction when goethite was absent and Fe(II) was present. Experiments were carried out with goethite at 30°C in which the total amount of Fe(II) in the system, the amount of sorbed Fe(II), the pH, and the density of sorbed Fe(II) were varied. Regeneration of sorbed Fe(II) occurred when dissolved Fe2+ was available and maintained pseudo-first-order conditions with respect to CT. Analysis of the CT loss rates for experiments with sorbed-Fe(II) regeneration revealed the rate-determining step to be first order with respect to CT, second order with respect to the volumetric concentration of sorbed Fe(II), and zero order with respect to H+ for pH 4.2-7.3. Normalization of the observed rate constants to account for various goethite concentrations gave reaction orders of zero and one, respectively for H+ and CT, and a second-order reaction with respect the density of sorbed Fe(II). The rate-determining step was a termolecular two-electron-transfer reaction involving two Fe2+ ions sorbed to adjacent sites on the goethite surface and CCl4 molecule approaching the surface. The primary role of the goethite surface was to catalyze the reaction by fixing the position of the two charged reactants in a geometry suitable for reaction with CT. In separate studies, biogenic Fe(II) formed by the enzymatic reduction of goethite by the Fe(III)-reducing bacterium Shewanella alga, strain BrY, dechlorinated CT. Dechlorination reactions in Fe(III)-reducing environments might indirectly result from the chemical or enzymatic reduction of Fe(III)-bearing minerals, e.g., goethite.

The kinetics of chlorination of several phenolic compounds and the corresponding formation of chloroform were investigated at room temperature. For the chlorination of phenolic compounds, second-order in the phenolic compound. The rate constants of the reactions of HOCl with phenol and phenolate anion and the rate constant of the acid-catalyzed reaction were determined in the pH range 1-11. The second-order rate constants for the reaction HOCl + phenol varied between 0.02 and 0.52 M-1 s-1, for the reaction HOCl and phenolate between 8.46 × 101 and 2.71 × 104 M-1 s-1. The rate constant for the acid-catalyzed reaction varied between 0.37 M-2 s-1 to 6.4 × 103 M-2 s-1. Hammett-type correlations were obtained for the reaction for the reaction of HOCl with phenolate (log(k) = 4.15-3.00 × ∑σ). The formation of chloroform could be interpreted with a second-order model, first-order in chlorine, and first-order in chloroform precursors. The corresponding rate constants varied between k > 100 M-1 s-1 for resorcinol to 0.026 M-1 s-1 to p-nitrophenol at pH 8.0. It was found that the rate-limiting step of chloroform formation is the chlorination of the chlorinated ketones. Yields of chloroform formation depend on the type and position of the substituents and varied between 2 and 95% based on the concentration of the phenol.

The reduction chemistry of cobalt complexes with HPNP (HPNP = HN(CH 2CH2PiPr2)2) as a supporting ligand is described. Reaction of [(HPNP)CoCl2] (1) with n-BuLi generated both the deprotonated Co(II) species [(PNP)CoCl] (2) along with the Co(I) complex [(HPNP)CoCl] (3). Products resulting from reduction of 2 with KC8 vary depending upon the atmosphere under which the reduction is performed. Monomeric square planar [(PNP)CoN2] (4) is obtained under dinitrogen, whereas dimeric [(PNP)Co]2 (5) is formed under argon. Over time, 5 activates a C-H bond in the PNP ligand to form the species [Co(H)(μ-PNP)(μ-iPr2PCH2CH 2NCHCH2PiPr2)Co] (6). We also observed the oxidative addition of H-Si bond to complex 3 to form [(HPNP)CoCl(H)SiH2Ph] (7). 1H NMR studies showed that species 7 is in equilibrium with 3 and silane in solution. Complex 3 can be oxidized with AgBPh4 to generate {(HPNP)CoCl}BPh4 (8), a square planar species with a formal electron count of 15 electrons.

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.

While reduction of chlorinated hydrocarbons by zero-valent iron in water is strongly influenced by the oxide layer at the metal-water interface, the role of the oxide in the dechlorination mechanism has not been fully characterized. In this paper, we investigate the semiconducting properties of the oxide layer on granular iron and show how the electronic properties of the oxide affect electron transfer to aqueous CCl4. Specifically, we determine whether conduction-band electrons contribute to the reduction of CCl4 by using light to increase the number of conduction-band electrons at the oxide surface and measuring how this treatment affects the rate and products of CCl4 degradation. We find that photogenerated conduction-band electrons do degrade CCl4 and, more importantly, shift the product distribution to more completely dechlorinated products that are indicative of two-electron transfer with a dichlorocarbene intermediate. Since the photogenerated electrons give different reduction products than the dark reducers, we conclude that the latter must not be conduction-band electrons. Further investigation of the reduction with photogenerated electrons is carried out by adding hole scavengers to the system. Isopropyl alcohol reacts with photogenerated holes to yield the ?±-hydroxyalkyl radical, which is known to reduce CCl4. With isopropyl alcohol present, we observe faster degradation of CCl4 with higher light intensity. Since no such increase is seen without isopropyl alcohol, the rate of CCl4 degradation by conduction-band electrons in water must not be limited by the number of photogenerated electron-hole pairs but rather by electron transfer from the oxide conduction band to CCl4.

Reduction of chlorinated solvents by fine-grained iron metal was studied in well-mixed anaerobic batch systems in order to help assess the utility of this reaction in remediation of contaminated groundwater. Iron sequentially dehalogenates carbon tetrachloride via chloroform to methylene chloride. The initial rate of each reaction step was pseudo-first-order in substrate and became substantially slower with each dehalogenation step. Thus, carbon tetrachloride degradation typically occurred in several hours, but no significant reduction of methylene chloride was observed over 1 month. Trichloroethene (TCE) was also dechlorinated by iron, although more slowly than carbon tetrachloride. Increasing the clean surface area of iron greatly increased the rate of carbon tetrachloride dehalogenation, whereas increasing pH decreased the reduction rate slightly. The reduction of chlorinated methanes in batch model systems appears to be coupled with oxidative dissolution (corrosion) of the iron through a largely diffusion-limited surface reaction.

To address some of the fundamental questions regarding the kinetics of reduction of contaminants by zero-valent iron (Fe0), we have taken advantage of the mass transport control afforded by a polished Fe0 rotating disk electrode (RDE) in an electrochemical cell. The kinetics of carbon tetrachloride (CCl4) dechlorination at an Fe0 RDE were studied in pH 8.4 borate buffer at a potential at which an oxide film would not form. In this system, the cathodic current was essentially independent of electrode rotation rate, and the measured first-order heterogeneous rate constant for the chemical reaction (k(ct) = 2.3 x 10-5 cm s-1) was less than the estimated rate constant for mass transfer to the surface. Thus, for the conditions of this study, the rate of reduction of CCl4 by oxide-free Fe0 appears to be dominated by reaction at the metal-water interface rather than by transport to the metal surface. Activation energies for reduction of CCl4 and hexachloroethane by oxide-covered granular Fe0 (measured in batch systems) also indicate that overall rates are limited by reaction kinetics. Since mass transport rates vary little among the chlorinated solvents, it is likely that variation in k(ct) is primarily responsible for the wide range of dechlorination rates that have been reported for batch and column conditions. To address some of the fundamental questions regarding the kinetics of reduction of contaminants by zero-valent iron (Fe0), we have taken advantage of the mass transport control afforded by a polished Fe0 rotating disk electrode (RDE) in an electrochemical cell. The kinetics of carbon tetrachloride (CCl4) dechlorination at an Fe0 RDE were studied in pH 8.4 borate buffer at a potential at which an oxide film would not form. In this system, the cathodic current was essentially independent of electrode rotation rate, and the measured first-order heterogeneous rate constant for the chemical reaction (kct = 2.3×10-5 cm s-1) was less than the estimated rate constant for mass transfer to the surface. Thus, for the conditions of this study, the rate of reduction of CCl4 by oxide-free Fe0 appears to be dominated by reaction at the metal - water interface rather than by transport to the metal surface. Activation energies for reduction of CCl4 and hexachloroethane by oxide-covered granular Fe0 (measured in batch systems) also indicate that overall rates are limited by reaction kinetics. Since mass transport rates vary little among the chlorinated solvents, it is likely that variation in kct is primarily responsible for the wide range of dechlorination rates that have been reported for batch and column conditions.

The dependence of the yield of products in the γ-radiation-induced free-radical reactions in carbon tetrachloride solutions of secondary alcohols on the alcohol concentration and the temperature was studied in the range of 0.05-0.6 M and 30-150 deg C.The rate constant for the reaction CCl3 + R1R2COH -> CHCl3 + R1R2COH (k1) was found as logk1 (M-1 s-1) = 8.63-9.1, where Τ = 2.303RT kcal mol-1.The activation energy is 1.8 +/- 0.3 kcal mol-1 lower than for secondary hydrogens in alkanes and about the same as for the tertiary hydrogens in 2,3-dimethylbutane.

A mechanistic study of the reductive dechlorination of carbon tetrachloride by vitamin B12 (cyanocobalamin) in the presence of dithiothreitol was conducted as a function of redox potential and pH. The solution redox potential decreased both with an increase in the total concentration of dithiothreitol present and with an increase in pH. The pseudo-first-order rate constant of carbon tetrachloride disappearance increased with decreasing redox potential. The predominant cobalt species present under the reaction conditions was cobalamin(II) (vitamin B12r), as confirmed by spectrophotometric analysis, suggesting a one-electron reduction of vitamin B12 and the involvement of two vitamin B12 molecules per reacting carbon tetrachloride molecule. -from Authors

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.

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.

The present invention provides processes to prepare carbon tetrachloride by the chlorination of natural gas in the presence of a diluent.

The present invention relates to a method of producing methyl chloride by multistage reactions. The method of the present invention comprises: a) a chlorination step for sufficiently increasing the conversion rate of methane, which is an initial reactant; and b) a subsequent reaction step for actively utilizing hydrogen chloride (HCl), which is a hazardous byproduct of chlorination, efficiently treating harmful hydrogen chloride, and at the same time, improving the overall production of methyl chloride.COPYRIGHT KIPO 2020

CH4 chlorination with Cl2 gas is used for the production of chlorinated products via C–H bond activation in CH4. Due to the high reactivity of Cl2, this reaction can occur spontaneously under UV irradiation or with mild thermal energy even in the absence of a catalyst via a free radical-mediated chain reaction mechanism that undesirably causes excessive chlorination of the CH4 and is thus non-selective. In this work, CH4 chlorination is investigated using HY and MFI zeolites with various Si/Al ratios, by which the reaction is catalytically controlled for selective production of the mono-chlorinated product (CH3Cl). Depending on the framework type, Si/Al ratio of the zeolites, and reaction conditions, different degrees of CH4 conversion, CH3Cl selectivity, and hence CH3Cl yield were achieved, by which systematic relationships between the catalyst properties and performance were discovered. A high aluminum content facilitated the production of CH3Cl with up to ～20 % yield at a high gas hourly space velocity of 2400 cm3gcat?1 h?1 with a CH4/Cl2 ratio of 1 at 350 °C. HY zeolites generally furnished a slightly higher CH3Cl yield than MFI zeolites, which can be attributed to the larger micropores of the HY zeolites that support facile molecular diffusion. With various flow rates and ratios of CH4 and Cl2, the CH4 conversion and CH3Cl selectivity changed simultaneously, with a trade-off relationship. Unfortunately, all zeolite catalysts suffered from framework dealumination due to the HCl produced during the reaction, but it was less pronounced for the zeolites having a low aluminum content. The results shed light on the detailed roles of zeolites as solid-acid catalysts in enhancing CH3Cl production during electrophilic CH4 chlorination.

Metalation of acetic, butanoic, or 2-methylpropanoic acid with lithium diisopropylamide in tetrahydrofuran under argon gave the corresponding lithium acylate α-carbanions which reacted with carbon tetrachloride at 20–25°C for 2 h to afford butanedioic acid or its 2,3-diethyl and 2,2,3,3-tetramethyl derivatives, as well as the corresponding α-chlorocarboxylic acids and chloroform. A radical mechanism was proposed for the formation of dicarboxylic and α-chlorocarboxylic acids.

Porous titanium dioxide pellets modified with copper(II) ion (Cu-TiO2) were synthesized by sol-gel method with dialysis for photocatalytic degradation of gaseous trichloroethylene (TCE) under visible light (VL) irradiation. TCE was completely degraded by passing the gas stream (mole fractions of oxygen and TCE were 0.2 and 1.75 × 10?4, respectively) at the flow rate of 25 mL min?1 through 0.2 g of the Cu-TiO2 pellets (Cu content: 0.1 atom%) calcined at 200 °C. TCE was converted mainly to carbon dioxide, dichloroacetic acid (DCAA), and inorganic chlorine species. Relatively small quantities of pentachloroethane (PCA) and trichloroacetaldehyde (TCAH) were detected as products on the Cu-TiO2 surface. Comparison with porous TiO2 pellets under ultraviolet irradiation revealed that more chlorinated products and less carbon dioxide were formed on Cu-TiO2 under VL irradiation. The mineralization of TCE to carbon dioxide was calculated to be only ca. 30.0%. It is noted that DCAA, PCA and TCAH were accumulated on the surface and were extracted with ethyl acetate. The porous Cu-TiO2 pellets show promise as the photocatalyst acting under VL irradiation for converting TCE gas to chlorinated compounds which can be used in industries.

A niobium doped high surface aluminium fluoride (HS-AlF3) catalyst was prepared, using an approach in which niobium doped aluminium hydroxide fluoride obtained via reaction of aqueous HF with the respective metal alkoxides in isopropanol is further fluorinated under flow of CHClF2 at 200 °C. A comparable procedure was used to synthesize a Nb-free variant for comparison. Both catalysts exhibit very strong Lewis acidic surface sites which are capable to activate strong carbon-halogen bonds at room temperature, just as the classical high-surface AlF3 (HS-AlF3), obtained by reacting aluminium isopropoxide with anhydrous HF, does. The catalysts were characterized by elemental analysis, P-XRD, MAS NMR spectroscopy, N2 adsorption, NH3-TPD, and pyridine photoacoustic FT-IR spectroscopy. In contrast to previously reported niobium doped HS-AlF3, which was prepared using anhydrous HF, the doped catalyst obtained via this aqueous HF-route shows excellent performance both in the isomerization of 1,2-dibromohexafluoropropane, a reaction that occurs only in the presence of the strongest Lewis acids, and in the cyclization of citronellal to isopulegol, a reaction which requires both, Lewis and Br?nsted acid sites.

A cost-effective and energy-efficient process is disclosed for converting a methane-containing gas to a methane sulfonyl halide comprising reacting the methane-containing gas, under illumination by a light emitting diode (LED) source, with a sulfuryl halide or a halogen in the presence of sulfur dioxide, whereby the methane sulfonyl halide is obtained for isolation or further reactions. The further reactions may sequentially include, in order, contacting the methane sulfonyl halide with a catalyst complex to form a methane monohalide; catalytically converting the methane monohalide to a value-added chemical such as an alcohol, an olefin, an aromatic, derivatives thereof, or mixtures thereof; releasing any hydrogen halide formed in the process; and converting the hydrogen halide to a halogen and recycling it for re-use.

The selective activation of C–Cl bonds of hydrochlorofluoromethanes and chloromethanes at moderate reaction conditions using ACF in a combination with Et3GeH is presented. The reactions of the chloromethanes (CH3Cl, CH2Cl2, CHCl3 and CCl4) in the presence of Et3GeH and ACF as catalyst led to the activation of only one C–Cl bond resulting in the hydrodechlorination. Friedel-Crafts reactions with benzene as solvent are suppressed by Et3GeH. A selective hydrodechlorination of hydrochlorofluoromethanes was achieved, because a transformation of a C–F bond into a C–H bond by the combination of ACF with Et3GeH did not occur. Supporting PulseTA experiments illustrated the interaction between the solid catalyst and Et3GeH, the solvent benzene or CH2Cl2.

In this study, UV irradiation combined with chlorine (UV/chlorine) was used to degrade naproxen (NPX), a typical non-steroidal anti-inflammatory drug (NSAID) widely used for the treatment of symptoms associated with inflammation, in water. Compared with UV irradiation alone and direct chlorination, the UV/chlorine process shows a synergistic effect on NPX degradation. The effects of different factors, including the chlorine dose, solution pH, and the presence of Cl-, HCO3- or humic acid (HA), on NPX degradation in the UV/chlorine process were investigated. The results indicated that the degradation of NPX followed pseudo-first-order kinetics in all cases, and the rate constant increased as the chlorine dose increased and decreased as the pH increased. The effects of the water matrix on UV/chlorine treatment were species-dependent. The NPX degradation rate was inhibited by the presence of HCO3- and HA but significantly improved by Cl-. LC/MS/MS analysis indicated that NPX decomposition in the UV/chlorine process was associated with decarboxylation, demethylation and hydroxylation. These results indicate that the UV/chlorine process is a promising technology for the treatment of water polluted by emerging contaminants, such as NPX. However, UV/chlorine can notably enhance the formation of disinfection by-products compared to direct chlorination, which should be carefully considered when integrating this process into drinking water treatment schemes.

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.

We report on the activation of chlorinated methanes by the heterogeneous catalysts aluminum chlorofluoride (ACF) and high-surface aluminum fluoride (HS-AlF3) under moderate conditions. For comparison, chlorinated toluenes and 1,2-dichloroethane

Water-soluble [RuCl(NHC)(L)(η6-arene)] complexes (NHC?=?bmim?=?1-butyl-3-methyl-imidazole-2-ylidene;?L?=?tertiary phosphine, such as mtppms, mtppts, pta, pta-Me and pta-Bn; η6-arene?=?η6-p-cymene) were succesfully applied for the first time as catalysts in hydrodehalogenation of organic halides by hydrogen transfer from aqueous Na-formate with turnover frequencies up to TOF?=?112?h?1 at 80?°C. Simultaneous to hydrodehalogenation, aqueous formate was also decomposed to H2 and HCO3?. In case of [RuCl(bmim)(pta)(η6-p-cymene)]Cl (pta?=?1,3,5-triaza-7-phosphaadamantane) a reaction mechanism is suggested on basis of kinetic and NMR measurements which accounts for both hydrodehalogenation and formate dehydrogenation and involves [RuH(bmim)(pta)(η6-p-cymene)]+ as the key catalytic species for both cycles.

Ruthenium modified cobalt oxides were prepared by (1) impregnating ruthenium chloride hydrate on cobalt oxides, Ru-supported catalysts (Ru/Co3O4), and (2) Ru-doped catalysts (Ru-Co3O4) where the ruthenium ions were added to the precursor solution, by a one-step sol-gel method with cobalt nitrate. The physicochemical properties of the catalysts were characterized by ICP, BET, XRD, HR-TEM, TPR, and XPS analysis. The effects of ruthenium were studied for the total oxidation of vinyl chloride. This Ru modifier was observed to enhance oxygenate formation. The different preparation methods made contributions to the different amounts of Ru4+ on the surfaces of the catalysts while Ru4+ would be in synergy with Co2+ concentration, and this also changed the chemical coordination of oxygen on the surface. Dispersion of Ru oxides on the cobalt oxides surface could not only improve the catalytic activity and stability on steam, but also decrease the amount of chlorinated by-products and increase HCl selectivity.

The invention provides a technique for preparing monochlorodifluoromethane by decomposing trifluoromethane. The technique comprises the steps of: feeding the raw materials trifluoromethane and methane chloride into a reactor filled with a catalyst in the mol ratio of 0.1-10, and carrying out a decomposition reaction at a temperature ranging from 150 to 350 DEG C for 3-30 seconds to obtain a mixture of trifluoromethane, methane chloride, dichloromonofluoromethane and monochlorodifluoromethane; obtaining monochlorodifluoromethane directly through separation, reacting dichloromonofluoromethane separated out with hydrogen fluoride to produce monochlorodifluoromethane, and separating out and recovering trifluoromethane and methane chloride in the mixture as the reaction mixture continuously. The method has the advantage that the harm on the environment caused by trifluoromethane emission is greatly avoided.

PROBLEM TO BE SOLVED: To provide a method for dechlorinating carbon tetrachloride and a method for producing dechlorinated material, which neither need high temperature and high pressure conditions nor need to use corrosive, inflammable, volatile, or highly toxic chemicals. SOLUTION: Provided is a method for producing a dechlorinated material by using carbon tetrachloride as a raw material and dechlorinating the carbon tetrachloride by the dechlorinating method, where an ionic liquid represented by the formula (1) is reacted to carbon tetrachloride. (In the formula, R1 to R4 each independently represent an alkyl group or an aryl group, a part of whose hydrogen atoms may be substituted; and A represents a phosphorus atom or a nitrogen atom.) COPYRIGHT: (C)2015,JPOandINPIT

Thermal treatment induces a modification in the nanostructure of carbon nanospheres that generates ordered hemi-fullerene-type graphene shells arranged in a concentric onion-type structure. The catalytic reactivity of these structures is studied in comparison with that of the parent carbon material. The change in the surface reactivity induced by the transformation of the nanostructure, characterized by TEM, XRD, X-ray photoelectron spectroscopy (XPS), Raman, and porosity measurements, is investigated by multipulses of Cl2 in inert gas or in the presence of CH4 or CO. The strained C-C bonds (sp2-type) in the hemi-fullerene-type graphene shells induce unusually strong, but reversible, chemisorption of Cl2 in molecular form. The active species in CH4 and CO chlorination is probably in the radical-like form. Highly strained C-C bonds in the parent carbon materials react irreversibly with Cl2, inhibiting further reaction with CO. In addition, the higher presence of sp3-type defect sites promotes the formation of HCl with deactivation of the reactive C-C sites. The nano-ordering of the hemi-fullerene-type graphene thus reduces the presence of defects and transforms strained C-C bonds, resulting in irreversible chemisorption of Cl2 to catalytic sites able to perform selective chlorination. Tidy up the carbon! CO and CH4 chlorination over hemi-fullerene-type graphene is described. The surface nano-ordering, induced by thermal treatment, transforms strained C-C bond sites resulting in irreversible Cl2 chemisorption to catalytic sites that are able to selectively chlorinate CO and CH4.

Two series of carbon-supported Pd-Au catalysts were prepared by the reverse "water-in-oil, W/O" method, characterized by various techniques and investigated in the reaction of tetrachloromethane with hydrogen at 423K. The synthesized nanoparticles were reasonably monodispersed having an average diameter of 4-6nm (Pd/C and Pd-Au/C) and 9nm (Au/C). Monometallic palladium catalysts quickly deactivated during the hydrodehalogenation of CCl4. Palladium-gold catalysts with molar ratio Pd:Au=90:10 and 85:15 were stable and much more active than the monometallic palladium and Au-richer Pd-Au catalysts. The selectivity toward chlorine-free hydrocarbons (especially for C2+ hydrocarbons) was increased upon introducing small amounts of gold to palladium. Simultaneously, for the most active Pd-Au catalysts, the selectivity for undesired dimers C2HxCly, which are considered as coke precursors, was much lower than for monometallic Pd catalysts. Reasons for synergistic effects are discussed. During CCl4 hydrodechlorination the Pd/C and Pd-Au/C catalysts were subjected to bulk carbiding.

Norit active carbon-supported Ni-Pd catalysts were prepared, by incipient wetness impregnation, from the metal chlorides NiCl2.6H2O and PdCl2. The catalysts were characterized by temperature-programmed reduction, X-ray diffraction, and scanning electron microscopy, and by temperature-programmed hydrogenation (TPH) of the catalysts after use. When the catalysts were used for gasphase hydrodechlorination (HDC) of 1,2-dichloroethane (1,2-DCA) and 1,1,2-trichloroethene (TCE), very high activity and stability at a relatively low reaction temperature (503 K) were observed. Hydrodechlorination of TCE led to formation of hydrocarbons as the main products. Use of Ni and Ni-Pd catalysts for hydrodechlorination of 1,2-DCA resulted in very high (~100 %) selectivity for ethene. TPH of the catalysts after use for HDC of 1,2-DCA and TCE revealed the presence of carbon and chlorine-containing deposits on the surfaces of the catalysts. Formation of the NiCx fcc phase and the Ni3C hcp carbide phase were detected for the monometallic nickel and Ni95Pd05 catalysts.

The reactivity of cobalt complexes supported by a PNP pincer ligand towards H2 varies depending on whether the N-donor atom is protonated; the synthesis of [(HPNP)CoCl(H)2] (2), [(PNP)CoH]2 (4), and the trihydride species [(HPNP)CoH3] (7) (HPNP = HN(CH 2CH2PiPr2)2) are described. The Royal Society of Chemistry 2014.

Disclosed are azulenocyanine analogue compounds derived from azulene, method of making the same, and their use as dye for dye-sensitized solar cell. The azulenocyanine analogue compounds according to the present invention comprise at least one anchoring group.

Processes for the production of tetrachloromethane are provided. The present processes involve catalyzing the chlorination of a feedstream comprising partially chlorinated methanes with a free radical initiator. Cost savings are thus provided relative to conventional processes that require the use of high temperatures and/or pressures, and safety concerns are alleviated or eliminated.

The invention relates to substituted 6-(2-hydroxybenzylamino)purines of general formula I, to their activity as cyclin-dependent kinases 2, 5, 7 and 9 inhibitors and to their use as medicaments, particularly in the treatment of disorders involving cell proliferation or inflammation. The invention further includes pharmaceutical compositions containing the substituted 6-(2-hydroxybenzylamino)purines.

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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.

The reaction kinetics of hydrodechlorination (HDCl) for a series of CH 4-xClx (x = 1-4) compounds were measured on a Pd/carbon catalyst. The rate of HDCl correlated with the C-Cl bond energy, suggesting scission of this bond in the molecularly adsorbed molecule is rate-determining. The measured reaction kinetics of the CH4-xClx compounds support a previously proposed Langmuir-Hinshelwood type reaction mechanism. Kinetic and isotope exchange experiments demonstrated the following: gas phase H2 and HCl are in equilibrium with surface H and Cl; adsorbed Cl is the most abundant surface intermediate; and irreversible scission of the first C-Cl bond is rate-determining. The overall hydrodechlorination reaction rate can be written as kKR-Cl[R-Cl]/(1 + KHCl[HCl]/KH2 1/2[H2]1/2). The activation energy of the rate-determining step was related linearly to the dissociation energy of the first C-Cl bond broken in a Broensted-Evans-Polanyi relationship. This behavior is in agreement with a previous study of CF3CF 3-xClx compounds. During the reaction of CH3Cl, CH2Cl2, and CHCl3 with deuterium, H-D exchange occurred in only 2%, 6%, and 9% of products, respectively. The increasing H-D exchange with Cl content suggests the steps which determine selectivity in these multipath, parallel reactions. The density functional theory (DFT)-calculated activation energies for the dissociation of the first C-Cl bond in the family of chlorinated methane compounds are in good agreement with the values extracted from kinetic modeling, suggesting that parameters estimated from DFT calculations may be used to estimate the reactivity of a particular chlorinated compound within a family of chlorocarbons.

The present invention is in relation to a dendritic molecule having symmetrically sited branches having four or more generations of dendrimers wherein the branch points are tertiary amines linked together with oxygen atom of ether and the heteroatoms are separated by a substituted or non-substituted linear three methylene linker. In addition the invention also provides a process to prepare such dendritic macromolecules.

Chemical Equation Presentation Promoted by CuCI/CCI4, a variety of sulfonyl azides and tertiary amines were successfully coupled to give sulfonyl amidine derivatives in good to excellent yields. A possible mechanism for this reaction Is discussed

The present invention is to provide a production process capable of selectively producing various kinds of fluorine-containing carbonate compounds without any inhibition in high yields without using phosgene and without producing hydrogen chloride as a by-product. The present invention relates to a process for producing a fluorine-containing compound having a carbonate bond by reacting a compound (1) with a fluorine-containing compound having an OH group. In the formula (1) shown below, X1 to X6 each represents a hydrogen atom or a halogen atom, at least one of X1 to X3 is a halogen atom, and at least one of X4 to X6 is a halogen atom.

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.

MW ArF laser irradiation of gaseous cis-dichloroethene results in fast decomposition of this compound and in deposition of solid ultrafine Cl- and H-containing carbonaceous powder which is of interest due to its sub-microscopic structure and possible reactive modification of the C-Cl bonds. The product was characterized by electron microscopy, and FTIR and Raman spectra and it was revealed that HCl, H2, and C/H fragments are lost and graphitic features are adopted upon heating to 700°C.

(Figure Presented) Pass the parcel: Activity experiments show that LaCl3 supported on carbon nanofibers is a highly active, selective, and stable catalyst for the H-Cl exchange reaction between CCl4 and CH2Cl2 to form CHCl3 (see scheme) in the absence of either lattice or gas-phase oxygen. Density functional calculations suggest that the reaction proceeds through the formation of weakly adsorbed Cl and H species which can be exchanged between the reactants.

The mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methane activation proceeds through oxidation-reduction reactions on the surface of catalysts with an irreducible metal-lanthanum, which is significantly different from known mechanisms for oxidative chlorination. Activity and spectroscopic measurements show that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with an intermediate extent of chlorination are all active for this reaction. The catalyst is stable with no noticeable deactivation after three weeks of testing. Kinetic measurements suggest that methane activation proceeds on the surface of the catalyst. Flow and pulse experiments indicate that the presence of hydrogen chloride is not required for activity, and its role appears to be limited to maintaining the extent of catalyst chlorination. In contrast, the presence of gas-phase oxygen is essential for catalytic activity. Density-functional theory calculations suggest that oxygen can activate surface chlorine species by adsorbing dissociatively and forming OCI surface species, which can serve as an active site for methane activation. The proposed mechanism, thus, involves changing of the formal oxidation state of surface chlorine from -1 to +1 without any changes in the oxidation state of the underlying metal.

Coupling reaction of polychloromethanes CH4-nCln (n = 2-4) with HSiCl3 in the presence of tetrabutylphosphonium chloride (Bu4PCl) as a catalyst occurred at temperatures ranging from 30 °C to 150 °C. The reactivity of polychloromethanes increases as the number of chlorine-substituents on the carbon increases. In the reactions of CCl4 with HSiCl3, a variety of coupling products such as bis(chlorosilyl)methanes CH2(SiCl3)(SiXCl2) [X = Cl (1a), H (1b)], (chlorosilyl)trichloromthanes Cl3CSiXCl2 [X = Cl (2a), H (2b)], and (chlorosilyl)dichloromthanes Cl2HCSiXCl2 [X = Cl (3a), H (3b)] were obtained along with reductive dechlorination products such as CHCl3 and CH2Cl2 depending on the reaction temperature. In the reaction of CCl4, 2a is formed at the initial stage of the coupling reaction and converted to give CHCl3 at low temperature of 30 °C, to give 1a, 3a, and CHCl3 at 60 °C, and to afford 1a as major product and CH2Cl2 in competition above 100 °C. Si-H bond containing silylmethanes can be formed by the H-Cl exchange reaction with HSiCl3. Reaction of CHCl3 with HSiCl3 took placed at 80 °C to give three compounds 1a, 3a, and CH2Cl2, and finally 3a was converted to give 1a and CH2Cl2 at longer reaction time. While the condition for the reaction of CH2Cl2 with HSiCl3 required a much higher temperature of 150 °C. Under the optimized conditions for synthesizing bis(chlorosilyl)methanes 1a,b, a mixture of 1a and 1b were obtained as major products in 65% (1a:1b = 64:1) and 47% (42:5) yields from the reaction of CCl4 and CHCl3 at 100 °C for 8 h, respectively, and in 41% (34:7) yield from that of CH2Cl2 at 170 °C for 12 h. In the Si-C coupling reaction of polychloromethanes with HSiCl3, it seems likely that a trichlorosilyl anion generated from the reaction of HSiCl3 with Bu4PCl is an important key intermediate.

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.

Trichlorobenzenes can be easily decomposed by alternating current electrolysis in aqueous solution. The mechanism of the decomposition was found to be based on selective redox reactions with different radicals - hydrogen atoms and hydroxyl radicals - generated by water electrolysis. Copyright

The influence of amine buffers on carbon tetrachloride (CCI4) reductive dechlorination by the iron oxide magnetite (FeIIFe II2O4) was examined in batch reactors. A baseline was provided by monitoring the reaction in a magnetite suspension containing NaCl as a background electrolyte at pH 8.9. The baseline reaction rate constant was measured at 7.1 × 10-5 ± 6.3 × 10-6 L m-2 h-1. Carbon monoxide (CO) was the dominant reaction product at 82% followed by chloroform (CHCI3) at 5.2%. In the presence of 0.01 M tris-(deuteroxymethyl) aminomethane (TRIS d), the reaction rate constant nearly tripled to 2.1 × 10 -4 ± 6.5 × 10-6 L m-2 h -1 but only increased the CHCI3 yield to 11% and did not cause any statistically significant changes to the CO yield. Reactions in the presence of triethylammonium (TEAd) (0.01 M) increased the rate constant by 17% to 8.6 × 10-5 ± 8.1 × 10 -6 L m-2 h-1 but only increased the CHCI 3 yield to 8.8% while leaving the CO yield unchanged. The same concentration of N,N,N′,N′-tetraethylethylenediamine (TEEN) increased the reaction rate constant by 18% to 8.7 × 10-5 ± 4.8 × 10-6 L m-2 h-1 but enhanced the CHCI3 yield to 34% at the expense of the CO yield that dropped to 35%. Previous work has shown that CHCI3 can be generated either through hydrogen abstraction by a trichloromethyl radical ( .CCI3), or through proton abstraction by the trichlorocarbanion (-:CCI3). These two possible hydrogenolysis pathways were examined in the presence of deuterated buffers. Deuterium tracking experiments revealed that proton abstraction by the trichlorocarbanion was the dominant hydrogenolysis mechanism in the magnetite-buffered TRISd and TEAd systems. The only buffer that had minimal influence on both the reaction rate and product distribution was TEAd. These results indicate that buffers should be prescreened and demonstrated to have minimal impact on reaction rates and product distributions prior to use. Alternatively, it may be preferable, to utilize the buffer capacity of the solids to avoid organic buffer interactions entirely.

The reactions of eight model contaminants with nine types of granular Fe(O) were studied in batch experiments using consistent experimental conditions. The model contaminants (herein referred to as "reductates" because they were reduced by the iron metal) included cations (Cu2+), anions (CrO42-, NO3-, and 5,5′,7,7′-indigotetrasulfonate), and neutral species (2-chloroacetophenone, 2,4,6-trinitrotoluene, carbon tetrachloride, and trichloroethene). The diversity of this range of reductates offers a uniquely broad perspective on the reactivity of Fe(O). Rate constants for disappearance of the reductates vary over as much as four orders of magnitude for particular reductates (due to differences in the nine types of iron) but differences among the reductates were even larger, ranging over almost seven orders of magnitude. Various ways of summarizing the data all suggest that relative reactivities with Fe(O) vary in the order Cu2+, 5,5′,7,7′ -indigotetrasulfonate > 2-chloroacetophenone, 2,4,6-trinitrotoluene > carbon tetrachloride, CrO42- > trichloroethene > NO3-. Although the reductate has the largest effect on disappearance kinetics, more subtle differences in reactivity due to the type of Fe(O) suggests that removal of CrO22- and NO 3- (the inorganic anions) involves adsorption to oxides on the Fe(O), whereas the disappearance kinetics of all other types of reductants is favored by reduction on comparatively oxide-free metal. Correlation analysis of the disappearance rate constants using descriptors of the reductates calculated by molecular modeling (energies of the lowest unoccupied molecular orbitals, LUMO, highest occupied molecular orbitals, HOMO, and HOMO-LUMO gaps) showed that reactivities generally decrease with increasing ELUMO and increasing EGAP (and, therefore, increasing chemical hardness η).

The use of a thermophilic cytochrome P450, CYP119, in electrocatalytic dehalogenations of C1 halocarbon solvents is studied. Temperature stable enzyme-modified electrodes were constructed using sol-gel and polymeric surfactant approaches. CYP119 deposited in a dimethyldidodecylammonium poly(p-styrene sulfonate) (DDAPSS) film has good retention of electrochemical activity up to 80 °C. At potentials approaching the FeII/I couple, the CYP119/DDAPSS films demonstrate high catalytic dehalogenations of the C1 chloromethanes CCl4, CHCl3, and CH2Cl2. Product analysis identified mixtures of sequentially dechlorinated products up to methane; no evidence for radical-coupled products was observed. The yield of methane from the CYP119-catalyzed reduction of CCl4 is increased 35-fold from 25 °C to 55 °C. In combination with the lack of C2 products, the facility of an overall eight-electron reductive dehalogenation suggests that the substrate is constrained within the protein during electrocatalytic turnover. Copyright

It is intended to provide novel labeling reagents characterized by having a group capable of binding to a substance to be labeled (for example, a biological substance, a physiologically active substance, etc.), easily forming a complex together with a rare earth ion, the complex being stable in an aqueous solution, and having a sufficient fluorescence intensity and a long fluorescence life time regardless of buffer types; complexes composed of the above labeling reagent with a rare earth ion; fluorescence labels containing the above complex; a fluorescence assaymethod using the above fluorescent label; etc. Namely, labeling reagents comprising a compound having a 2, 2' :6', 2 -tripyridine skeleton or a 2, 6-dipyrazolopyridine skeleton and having a group capable of binding to a substance to be labeled (for example, a biological substance, a physiologically active substance, etc.) and a group capable of forming a complex together with a rare earth ion; complexes composed of the above labeling reagent with a rare earth ion; fluorescence labels containing the above complex; a fluorescence labeling method using the above complex as a label; and a fluorescence assay method using the above fluorescent label.

The invention concerns a method for making an alkanesulponyl chloride by photochemical reaction of an alkane with chlorine and sulphur dioxide, which consists in using as light source an indium-doped medium-pressure mercury lamp.

Fe(II) associated with iron-containing minerals has been shown to be a potential reductant in natural subsurface environments. While it is known that the surface-bound iron species has the capacity to dechlorinate various chlorinated compounds, the role of transition metals to act as catalysts with these iron species is of importance. We previously observed that the reduction of Cu(II) by Fe(II) associated with goethite enhanced the dechlorination efficiency of chlorinated compound. In this study, the reductive dechlorination of carbon tetrachloride (CCl4) by dissolved Fe(II) in the presence of Cu(II) ions was investigated to understand the synergistic effect of Fe(II) and Cu(II) on the dechlorination processes in homogeneous aqueous solutions. The dechlorination efficiency of CCl4 by Fe(II) increased with increasing Cu(II) concentrations over the range of 0.2-0.5 mM and then decreased at high Cu(II) concentrations. The efficiency and rate of CCl4 dechlorination also increased with increasing dissolved Fe(II) concentration in the presence of 0.5 mM Cu(II) at neutral pH. When the Fe(II)/Cu(II) ratio varied between 1 and 10, the pseudo-first-order rate constant (fabs) increased 250-fold from 0.007 h-1 at 0.5 mM Fe(II) to 1.754 h-1 at 5 mM Fe(II). X-ray powder diffraction and scanning electron microscopy analyses showed that Cu(II) can react with Fe(II) to produce different morphologies of ferric oxides and subsequently accelerate the dechlorination rate of CCl4 at a high Fe(II) concentration. Amorphous ferrihydrite was observed when the stoichiometric Fe(II)/Cu(II) ratio was 1, while green rust, goethite, and magnetite were formed when the molar ratios of Fe(II)/Cu(II) reached 4-6. In addition, the dechlorination of CCl4 by dissolved Fe(II) is pH dependent. CCl4 can be dechlorinated by Fe(II) over a wide range of pH values in the Cu(II)-amended solutions, and the kobs increased from 0.0057 h-1 at pH 4.3 to 0.856 h-1 at pH 8.5, which was 9-25 times greater than that in the absence of Cu(II) at pH 7-8.5. The high reactivity of dissolved Fe(II) on the dechlorination of CCl4 in the presence of Cu(II) under anoxic conditions may enhance our understanding of the role of Fe(II) and the long-term reactivity of the zerovalent iron system in the dechlorination processes for chlorinated organic contaminants.

The invention relates to novel benzofuran derivatives and their use as active ingredients in the preparation of pharmaceutical compositions. The invention also concerns related aspects including processes for the preparation of the compounds, pharmaceutical compositions containing one or more of those compounds and especially their use as anti-infectives.

Peptide-based gemini compounds comprising basic amino acid chains linked by at least epsilon amide bond, showing improved DNA transfection properties, are disclosed. Methods for production of the compounds and the uses thereof are also disclosed.