- ArF laser photolytic deposition and thermal modification of an ultrafine chlorohydrocarbon
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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.
- Pola, Josef,Galikova, Anna,Subrt, Jan,Ouchi, Akihiko
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Read Online
- Reductive capacity of natural reductants
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The reductive capacities of soil minerals and Silawa soil for Cr(VI) and chlorinated ethylenes were determined and characterized to understand in situ treatment using these natural reductions. The reductive capacity of soil minerals for Cr(VI) was 3-16 times greater than that for tetrachloroethylene (PCE), indicating that Cr(VI) is more susceptible to the reduction by soil minerals than PCE. Green rust (GRSO4) showed the greatest reductive capacity for Cr(VI) and PCE followed by magnetite, pyrite, biotite, montmorillonite, and vermiculite. The major transformation product in pyrite and GRSO4 suspensions was acetylene rather than dichloroethylene (DCE) and vinyl chloride (VC). For VC degradation, ethylene was the main transformation product with a low concentration of ethane observed. Fe(II) content in soil minerals was directly proportional to the reductive capacity of soil minerals for Cr(VI) and PCE, suggesting that Fe(II) content is an important factor that significantly affects reductive transformations of target contaminants in natural systems.
- Lee, Woojin,Batchelor, Bill
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- Mercury-photosensitized reactions of cis-2-butene-ethanol and cis-2-butene-propylamine mixtures
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The Hg(3P1)-photosensitized luminescence of propylamine (PA) and ethanol (ET) and the Hg(3P1)-photosensitized isomerization of cis-2-butene (cis-2B) were studied in ET-cis-2B and PA-cis-2B mixtures under steady illumination at room temperature. The decreases in intensities of the luminescence from the HgPA* and HgET* complexes by adding cis-2B were much steeper than those anticipated by the competitive quenching of Hg(3P1) by PA (ET) and cis-2B. However, the decreases of the isomerization rate of cis-2B by additions of ET and PA were smaller than those expected by the competitive quenching by PA (ET) and cis-2B. The findings for PA-cis-2B mixtures could be explained by considering the addition reaction Hg(3P0) + cis-2B → Hg(1S0) + B* (B* = triplet state of 2-butene). Although HgCl formation was predominant and no cis-trans isomerization was observed in the Hg(3P1)-photosensitized reaction of cis- and trans-1,2-dichloroethylene (DCE) the isomerization of DCE in the photosensitized reaction of DCE-ET [DCE]0:[ET]0 = 1:100) mixture could be followed. These results could also be explained by the reaction HgET* + DCE → Hg(1S0) + ET + DCE*. This kind of reaction was proposed for the first time.
- Yamamoto,Kasamatsu,Sueishi
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Read Online
- Preparation and reactivity of vitaminB12-TiO2 hybrid catalyst immobilized on a glass plate
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The vitaminB12-TiO2 hybrid catalyst was effectively immobilized on a glass plate, and the immobilized catalyst shows an efficient reactivity for various molecular transformations, such as the 1,2-migration of a phenyl group and dechlorination of perchloroethylene during irradiation by UV light.
- Shimakoshi, Hisashi,Abiru, Makoto,Kuroiwa, Keita,Kimizuka, Nobuo,Watanabe, Midori,Hisaeda, Yoshio
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experimental part
p. 170 - 172
(2010/05/15)
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- Composition For the Vapor Phase Dehydrohalogenation of 1,1,2-Trihaloethane To 1,1-Dihaloethylene and Methods For Preparing and Using Such Composition
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Described are compositions adapted to catalyze the vapor phase dehydrohalogenation of 1,1,2-trihaloethane to 1,1-dihaloethylene, e.g., 1,1,2-trichloroethane to vinylidene chloride. These materials include activated carbon and at least one benzimidazole-containing material defined herein as including benzimidazole, a derivative thereof, a salt thereof or mixtures thereof. Also described are methods for producing and using these catalytic compositions.
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Page/Page column 7-10; 15
(2008/12/07)
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- COMPOSITION FOR THE VAPOR PHASE DEHYDROHALOGENATION OF 1,1,2-TRIHALOETHANE TO 1,1-DIHALOETHYLENE AND METHODS FOR PREPARING AND USING SUCH COMPOSITIONS
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Described are compositions adapted to catalyze the vapor phase dehydrohalogenation of 1,1,2-trihaloethane to 1,1-dihaloethylene, e.g., 1,1,2-trichloroethane to vinylidene chloride. These materials include activated carbon and at least one benzimidazole-containing material defined herein as including benzimidazole, a derivative thereof, a salt thereof or mixtures thereof. Also described are methods for producing and using these catalytic compositions.
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Page/Page column 16-27; 31-32
(2010/11/25)
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- Method for recovering trans-1,2-dichloroethene
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Describes a method for recovering trans-1,2-dichloroethene from a liquid feed composition comprising both the cis- and trans-isomers of 1,2-dichloroethene and contaminating amounts of other chlorinated hydrocarbons, e.g., lower alkyl chlorinated hydrocarbons, such as C1-C2 chlorinated hydrocarbons. In one of the described methods, the liquid feed composition is introduced into a first distillation column 10 wherein the stereoisomers and chlorinated hydrocarbons more volatile than the stereoisomers are removed as overhead 12 and charged to a second distillation column 20. In column 20, the stereoisomers are separated from the more volatile chlorinated hydrocarbons, and a bottoms fraction 24 comprising the stereoisomers are charged to a reaction distillation column 30 wherein the cis-isomer, is isomerized to the trans-isomer in the liquid phase and in the presence of an organic free-radical initiator, e.g., an azonitrile initiator. Substantially pure trans-1;2-dichloroethene is recovered as overhead 32 from reaction distillation column 30.
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Page/Page column 6-7
(2008/06/13)
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- Isotopic fractionation during reductive dechlorination of trichloroethene by zero-valent iron: Influence of surface treatment
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During reductive dechlorination of trichloroethene (TCE) by zero-valent iron, stable carbon isotopic values of residual TCE fractionate significantly and can be described by a Rayleigh model. This study investigated the effect of observed reaction rate, surface oxidation and iron type on isotopic fractionation of TCE during reductive dechlorination. Variation of observed reaction rate did not produce significant differences in isotopic fractionation in degradation experiments. However, a small influence on isotopic fractionation was observed for experiments using acid-cleaned electrolytic iron versus experiments using autoclaved electrolytic iron, acid-cleaned Peerless cast iron or autoclaved Peerless cast iron. A consistent isotopic enrichment factor of ε = -16.7‰ was determined for all experiments using cast iron, and for the experiments with autoclaved electrolytic iron. Column experiments using 100% cast iron and a 28% cast iron/72% aquifer matrix mixture also resulted in an enrichment factor of -16.9‰. The consistency in enrichment factors between batch and column systems suggests that isotopic trends observed in batch systems may be extrapolated to flowing systems such as field sites. The fact that significant isotopic fractionation was observed in all experiments implies that isotopic analysis can provide a direct qualitative indication of whether or not reductive dechlorination of TCE by Fe0 is occurring. This evidence may be useful in answering questions which arise at field sites, such as determining whether TCE observed down-gradient of an iron wall remediation scheme is the result of incomplete degradation within the wall, or of the dissolved TCE plume bypassing the wall.
- Slater,Sherwood Lollar,Allen King,O'Hannesin
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p. 587 - 596
(2007/10/03)
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- Pd-catalyzed TCE dechlorination in water: Effect of [H2](aq) and H2-utilizing competitive solutes on the TCE dechlorination rate and product distribution
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The aqueous-phase H2 concentration ([H2](aq)) and the presence of H2-utilizing competitive solutes affect trichloroethylene (TCE) dechlorination efficiency in Pd-based in-well treatment reactors. Batch kinetic studies in m
- Reinhard,Lowry
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p. 696 - 702
(2007/10/03)
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- Kinetics of the transformation of halogenated aliphatic compounds by iron sulfide
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The transformation of nine halogenated aliphatic compounds, i.e., pentachloroethane (PCA), 1,1,2,2- and 1,1,1,2-tetrachloroethanes (1122-TeCA and 1112-TeCA), 1,1,1- and 1,1,2-trichloroethanes (111-TCA and 112-TCA), 1,1- and 1,2-dichloroethanes (11-DCA and 12-DCA), carbon tetrachloride (CT), and tribromomethane (TBM), by 10 g/L FeS at pH 8.3 was investigated in batch experiments. 11-DCA, 12-DCA, and 112-TCA showed no significant transformation by FeS over ~ 120 days, but the other compounds were transformed with half-lives of hours to days. PCA and 1122-TeCA underwent dehydrohalogenation faster than FeS-mediated reductive dehalogenation reactions. The remaining compounds for which considerable transformation was observed underwent FeS-mediated reactions more rapidly than hydrolysis or dehydrohalogenation. For 1112-TeCA, the dihaloelimination product, i.e., 1,1-dichlroethylene, was the only reaction product observed. For 111-TCA, CT, and TBM, hydrogenolysis products were the only products detected, even though their mass recoveries were significantly 100%. Two simple log-linear correlations between rate constants and either one-electron reduction potentials or homolytic bond dissociation enthalpies were developed, with determination coefficients of 0.48 and 0.82, respectively. These results were consistent with a rate-limiting step involving homolytic bond dissociation. However, neither correlation precisely characterized the reactivity of all the compounds, indicating distinctions among the mechanisms for reductive dehalogenation of the compounds by FeS or the influence of additional molecular or thermodynamic parameters on rate constants.
- Hayes,Butler
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p. 422 - 429
(2007/10/03)
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- Pathways of chlorinated ethylene and chlorinated acetylene reaction with Zn(O)
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To successfully design treatment systems relying on reactions of chlorocarbons with zero-valent metals, information is needed concerning the kinetics and pathways through which transformations occur. In this study, pathways of chlorinated ethylene reaction with Zn(O) have been elucidated through batch experiments. Data for parent compound disappearance and product appearance were fit to pseudo-first-order rate expressions in order to develop a complete kinetic model. Results indicate that reductive β- elimination plays an important role, accounting for 15% of tetrachloroethylene (PCE), 30% of trichloroethylene (TCE), 85% of cis- dichloroethylene (cis-DCE), and 95% of trans-dichloroethylene (trans-DCE) reaction. The fraction of PCE, TCE, trans-DCE, and cis-DCE transformation that occurs via reductive elimination increases as the two-electron reduction potential (E2) for this reaction becomes more favorable relative to hydrogenolysis. In the case of PCE and TCE, reductive elimination gives rise to chlorinated acetylenes. Chloroacetylene and dichloroacetylene were synthesized and found to react rapidly with zinc, displaying products consistent' with both hydrogenolysis and reduction of the triple bond. Surface area-normalized rate constants (k(SA))for chlorinated ethylene disappearance correlate well with both one-electron (E1) and two-electron (E2) reduction potentials for the appropriate reactions. Correlation with E2 allows prediction of the distribution of reaction products as well as the rate of disappearance of the parent compound. To successfully design treatment systems relying on reactions of chlorocarbons with zero-valent metals, information is needed concerning the kinetics and pathways through which transformations occur. In this study, pathways of chlorinated ethylene reaction with Zn(0) have been elucidated through batch experiments. Data for parent compound disappearance and product appearance were fit to pseudo-first-order rate expressions in order to develop a complete kinetic model. Results indicate that reductive β-elimination plays an important role, accounting for 15% of tetrachloroethylene (PCE), 30% of trichloroethylene (TCE), 85% of cis-dichloroethylene (cis-DCE), and 95% of trans-dichloroethylene (trans-DCE) reaction. The fraction of PCE, TCE, trans-DCE, and cis-DCE transformation that occurs via reductive elimination increases as the two-electron reduction potential (E2) for this reaction becomes more favorable relative to hydrogenolysis. In the case of PCE and TCE, reductive elimination gives rise to chlorinated acetylenes. Chloroacetylene and dichloroacetylene were synthesized and found to react rapidly with zinc, displaying products consistent with both hydrogenolysis and reduction of the triple bond. Surface area-normalized rate constants (kSA) for chlorinated ethylene disappearance correlate well with both one-electron (E1) and two-electron (E2) reduction potentials for the appropriate reactions. Correlation with E2 allows prediction of the distribution of reaction products as well as the rate of disappearance of the parent compound.
- Arnold, William A.,Lynn Roberts
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p. 3017 - 3025
(2007/10/03)
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- Corrinoid-mediated reduction of tetrachloroethene, trichloroethene, and trichlorofluoroethene in homogeneous aqueous solution: Reaction kinetics and reaction mechanisms
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It is shown that in homogeneous aqueous solution containing titanium(III) citrate or titanium(III)-NTA as bulk electron donor, cobalamin, cobinamide, and cobamide are effective electron transfer mediators for the reduction of tetrachloroethene (PCE), trichloroethene (TCE), and trichlorofluoroethene (TCFE). For a given chlorinated ethene, the reaction rate varied only slightly with pH and type of corrinoid present and was about 5 and 50 times faster for PCE as compared to TCFE and TCE, respectively. Evidence is presented that the first and rate-limiting step of the reduction of PCE, TCE, and TCFE by super-reduced corrinoids is a dissociative one- electron transfer yielding the corresponding vinyl radicals. Furthermore, the elimination of a chloride radical from the 1,1-dichlorovinyl radical yielding chloroacetylene and subsequently acetylene is proposed to account for the direct formation of acetylene out of TCE. Finally, it is demonstrated that at higher reduction potentials the corrinoid mediators may be blocked by the formation of addition products.
- Glod, Guy,Angst, Werner,Holliger, Christof,Schwarzenbach, Rene P.
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p. 253 - 260
(2007/10/03)
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- Reductive Dechlorination of Tetrachloroethylene and Trichlproethylene Catalyzed by Vitamin B12 in Homogeneous and Heterogeneous Systems
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The reduction of tetrachloroethylene (PCE) and trichloroethylene (TCE) catalyzed by vitamin B12 was examined in homogeneous and heterogeneous (B12 bound to agarose) batch systems using titanium(III) citrate as the bulk reductant. The solution and surface-mediated reaction rates at similar B12 loadings were comparable, indicating that binding vitamin B12 to a surface did not lower catalytic activity. No loss in PCE reducing activity was observed with repeated usage of surface-bound vitamin B12. Carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction, relative to controls. In addition to sequential hydrogenolysis, a second competing reaction mechanism for the reduction of PCE and TCE by B12, reductive β-elimination, is proposed to account for the observation of acetylene as a significant reaction intermediate. Reductive β-elimination should be considered as a potential pathway in other reactive systems involving the reduction of vicinal polyhaloethenes. Surface-bound catalysts such as vitamin B12 may have utility in the engineered degradation of aqueous phase chlorinated ethenes.
- Burris, David R.,Delcomyn, Carrie A.,Smith, Mark H.,Lynn Roberts
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p. 3047 - 3052
(2007/10/03)
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- Rearrangement of alkylchlorocarbenes: 1,2-H shift in free carbene, carbene-olefin complex, and excited states of carbene precursors
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Photolysis of alkylchlorodiazirines (1) in the presence of olefins gives a cyclopropane (3) by addition of the generated carbene to the olefin and a vinyl chloride derivative (2) resulting from a 1,2-H shift rearrangement. This rearrangement may occur either in the carbene or in some excited state, precursor of the carbene (RIES mechanism), or in a 'carbene + olefin complex' on the way to the formation of 3 (COC mechanism). Results obtained by time-resolved photoacoustic calorimetry as well as by thermolysis and photolysis of ClCH2C(N2)Cl and CH3(CH2)2C(N2)Cl in the presence of tetramethylethylene clearly indicate that both the RIES and COC mechanisms play a role but with efficiencies which greatly depend on the nature of the diazirine. Reexamination of the results previously obtained with benzylchlorodiazirines indicates that, for this class of diazirines, the RIES mechanism is temperature dependent and has a very low efficiency at room temperature and below, whereas the nonlinearity of the plots [3]/[2] vs [olefin] is mainly due to the COC mechanism.
- Bonneau, Roland,Liu, Michael T. H.,Kim, Kyu Chul,Goodman, Joshua L.
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p. 3829 - 3837
(2007/10/03)
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- A Method for the Rapid Dechlorination of Low Molecular Weight Chlorinated Hydrocarbons in Water
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1,1,2-Trichloroethylene (TCE), 1,1-dichloroethylene, cis and trans-1,2-dichloroethylene and tetrachloroethylene (PCE), at concentrations of 20 ppm in aqueous solutions were rapidly hydrodechlorinated to ethane (in a few minutes), on the surface of palladized iron in batch experiments that were performed in closed vials. No intermediate reaction products such as 1,1-dichloroethylene, 1,2-dichloroethylenes and vinyl chloride were detected at concentrations > 1 ppm either in the headspace or in solution. The chloromethanes, CCl4, CHCl3 and CH2Cl2 were also dechlorinated to methane on palladized iron; the CCl4 was dechlorinated in a few minutes, the CHCl3, in less than an hour and the CH2Cl2, in 4-5 h. These results indicate that an above-ground treatment method can be designed for the treatment of groundwater contaminated with low molecular weight chlorinated hydrocarbons.
- Muftikian, Rosy,Fernando, Quintus,Korte, Nic
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p. 2434 - 2439
(2007/10/03)
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- Reductive Dechlorination of Tetrachloroethylene by a Chlorobenzoate-Enriched Biofilm Reactor
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This study evaluates the potential and technical feasibility of treating chloroaliphatics, common groundwater contaminants, using a specialized microbial consortium under fixed-film conditions. The reactor was developed using 3-chlorobenzoate (3-CB) as a substrate under anaerobic conditions and the enrichment that harbored an unusual dechlorinator, Desulfomonile tiedjei DCB-1. The dechlorination rate of both PCE and 3-CB increased with increasing flow rates up to 50 mL/h. The maximum observed dechlorination rates of PCE and 3-CB fed at 6.0 and 1000 μM were 2.0 and 414 μmol L h-1, respectively. This corresponds to a PCE consumption rate of 3.7 nmol h-1 (mg of protein)-1 -1 day-1>. The rate of PCE dechlorination increased from 2.0 to 10.3 μmol L-1 h-1 when the influent PCE was increased from 6.0 to 120 μM, respectively; however, concentrations of 60 μM and above damaged reactor performance. PCE was mainly converted to TCE and cis- and trans-DCE at all the tested flow rates. Vinyl chloride (VC) was never detected, thus suggesting dechlorination of PCE to non-chlorinated products. Although the PCE dechlorination activity of the biofilm was dependent on 3-CB, the activity could be sustained for 4-5 days on cheaper substrates such as acetate or benzoate after a 1-day pulse feeding of 3-CB. In addition to PCE dechlorination, the biofilm also dechlorinated other compounds such as chloroform (CF) and 1,1,2-trichloroethane (1,1,2-TCA). The present study is important, since D. tiedjei was previousely shown to dechlorinate many other chloroaromatic and aliphatic compounds.
- Fathepure, Babu Z.,Tiedje, James M.
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p. 746 - 752
(2007/10/03)
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- FTIR Study of the Cl + C2H2 Reaction: Formation of cis- and trans-CHCl=CH Radicals
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FTIR spectroscopic studies of the photolysis (λ >/= 300 nm) of mixtures containing Cl2 and C2H2, cis-CHCl=CHCl, or trans-CHCl=CHCl were carried out in 700 Torr of N2 at 295 +/- 2 K.On the basis of the kinetic analysis of cis- and trans-CHCl=CHCl formed from C2H2, the branching ratio k1a/k1b has been determined to be 0.19 +/- 0.05.Cl + C2H2 (+M) -> cis=ClCH-CH (+M); Cl + C2H2 (+M) -> trans-ClCH=CH (+M).Implications of these results for our previously postulated mechanism of Cl atom initiated oxidation of C2H2 are discussed.
- Zhu, T.,Yarwood, G.,Chen, J.,Niki, H.
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p. 5065 - 5067
(2007/10/02)
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- Isomeric Product Distributions from Solid-State Chain Reactions and Low-Temperature Microexplosions of Acetylene and Chlorine
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Free-radical chain reaction of acetylene and chlorine is initiated by pulsed ultraviolet photolysis of disordered solid films of these reagents at 10-60 K.The product (identified by FTIR spectroscopy) is a mixture of Z (cis) and E (trans) isomers of 1,2-dichloroethene.At 60 K in an equimolar mixture of reagents the photochemical quantum yield is 25 +/- 4; the isomeric product distribution is / = 10.2 +/- 1.5.At 10-30 K samples exhibit a sudden burst of reactivity (a microexplosion) after exposure to a cumulative laser fluence of 1-12 mJ/cm2 at 337 nm.The isomeric product distribution under these conditions is 2.9 +/- 0.4.The results demonstrate that reaction conditions during these microexplosions are characterized by high temperature and high mobility associated with transient liquefaction of the sample.
- Ovchinnikov, Mikhail A.,Wight, Charles A.
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p. 5411 - 5414
(2007/10/02)
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- Xenon Matrix Photochemistry of 1,1-Dichloroethene: Matrix-Dependent Surface Crossing and Hydrogen-Bonding Geometries
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The photoproducts of 1,1-dichloroethene (DCE) in Xe matrix at 12 K differ from those observed in Kr.With 239-nm photolysis, chlorine is eliminated from 1,1-DCE in solid Xe, but not in Kr, although HCl elimination and DCE isomerization occur in both matrices.Just as in the 1,2-dichloroethenes, Cl2 elimination proceeds in the heavy Xe matrix via spin-orbit-enhanced intersystem crossing to a triplet reaction surface.At higher photolysis energies, a novel product appears in Xe and is identified with the aid of isotopic substitution as a second HCl*C2HCl isomer, ?-hydrogen-bonded through the acetylenic proton.The product dependence on wavelength, parent, and matrix indicates that it is formed through a triplet-surface process under geometric constraints specific to the 1,1 isomer.Loss of Cl from a dissociative triplett state to form an excited chlorovinyl radical, with further cage reaction of the energetic fragments, is postulated.
- Laursen, Sandra L.,Pimentel, George C.
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p. 8175 - 8182
(2007/10/02)
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- CO2 Laser-induced Decomposition of 1,1,2-Trichloroethane
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CH2ClCHCl2 was photolyzed with a focusing geometry using the P(24) line of the 10.6 μm CO2 band (940.6 cm-1).The final products of neat photolysis were cis- and trans-CHCl=CHCl, CH2=CCl2, CH2=CHCl, CHCCl, CHCH, and C4H2.The relative yield of CH2=CCl2 in particular was strongly dependent on CH2ClCHCl2 pressure and sensitive to the addition of H atom containing molecules.A series of diagnostic experiments shows that the dichloroethene isomers are formed by three different processes, i.e., infrared multiphoton decomposition, collision-induced decomposition, and radical chain reaction.Infrared multiphoton decomposition and collision-induced decomposition give rise to cis- and trans-CHCl=CHCl predominantly, while the radical chain reaction generates the dichloroethane isomers in comparable amounts at high reactant pressures, the most probable initiation step being the C-Cl bond-scission reaction of the parent molecule.Formation mechanisms for other minor products are also discussed.
- Ogura, Hiroo
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p. 3528 - 3534
(2007/10/02)
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- Synthesis and reactivity of (chlorovinyl)nickel complexes: An unusual symmetrization reaction. X-ray crystal structure of [Ni(CCl=CCl2)2(PMe2Ph)2]
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The oxidative addition of CCl2=CCl2, CCl2=CHCl, trans-CHCl=CHCl, and CH2=CCl2 to [Ni(PPh3)n], prepared in situ from NiCl2, PPh3, and NaBH4, gives square-planar trans-[NiCl]chlorovinyl)(PPh3)2]. The addition takes place at the less hindered C-Cl bond, with retention of geometry. The PPh3 ligand is replaced by dppe in [NiCl(C2Cl3)(PPh3)2] giving [NiCl(C2Cl3)dppe] whereas the action of N-donor bidentate ligands gives a symmetrization reaction, forming [NiCl2(LL)] and [Ni(C2Cl3)2(LL)] (LL = 2,2′-bpy and o-phen). The ligand bpy may be replaced by phosphines like PMe2Ph and PEt3 in the trichlorovinyl complex. The crystal structure of trans-[Ni(C2Cl3)2(PMe2Ph) 2] (monoclinic, space group P21/c, a = 9.203 (2) ?, b = 16.005 (3) ?, c = 9.604 (2) ?, β = 114.79 (3)°, Z = 2) shows the presence of the anti and syn isomere in the solid. The Ni-P bond distance and the mean Ni-C bond distance are 2.201 (1) and 1.91 (1) ?, respectively. 31P and 13C NMR spectra indicate that similar amounts of syn and anti isomers are present in solution.
- Carvajal, Jorge,Muller, Guillermo,Sales, Joaquim,Solans, Xavier,Miravitlles, Carles
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p. 996 - 1002
(2008/10/08)
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- Catalytic dehydrohalogenation process
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Saturated C1-6 hydrochlorocarbons are dehydrochlorinated by contacting with ZSM-5 or silicalite zeolites at 200° C.-400° C.
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- Determination of Arrhenius parameters for unimolecular reactions of chloroalkanes by IR laser pyrolysis
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A simple and reliable method is elaborated for accurate measurements of thermal rate constants of homogeneous gas phase unimolecular reactions.A pulse of CO2 laser radiation was used to multiphoton excite SiF4 sensitizer molecules and consequently produce temperatures in the range 1100-1400 K.Expansion of the heated gas column quenches pyrolysis reactions on a 10 μs time scale.There are no hot surfaces to induce chemistry.HCl elimination from C2H5Cl, Ea = 57.4 kcal/mol and log A(s-1) = 13.8, was used as an internal temperature standerd.For the molecular elimination CCL3CH3 -> HCl + CCl2CH2, Ea = 49.5 +/- 1.3 kcal/mol and log A(s-1) = 13.1 +/- 0.3, were determined.In these experiments the major decomposition products of CHCl2CH2Cl are HCl and cis- or trans-CHClCHCl with Ea = 58.5 +/-2, log A = 14.1 +/- 0.4 and Ea = 59.5 +/- 2, log A = 13.9 +/- 0.4, respectively.HCl elimination to give CCl2CH2 and C-Cl bond breaking to CHClCH2Cl radical have higher activation energies.The method is generally useful for kinetics at high temperature.
- Dai, Hai-Lung,Specht, Eliot,Berman, Michael R.,Moore, C. Bradley
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p. 4494 - 4506
(2007/10/02)
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- Process for the manufacture of 1,2-dichloroethane
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A process for the manufacture of 1,2-dichloroethane is described, in which 1 mol of ethylene, 0.35 to 0.7 mol of chlorine, 0.7 to 1.4 mol of hydrogen chloride and 0.2 to 0.6 mol of oxygen, optionally together with inert gas, are reacted in a reaction zone containing surfaces capable of being heated and cooled, at 180° to 260° C. and under a pressure of 0.09 to 1.1 MPa, in the presence of a fixed bed catalyst containing copper. The process allows better utilization of the heat generated in the chlorination of ethylene.
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