156-59-2Relevant articles and documents
PHOTOSENSITIZED REACTION OF Hg(3P) ATOMS WITH THE DICHLOROETHENES IN KRYPTON MATRIX: TRIPLET SURFACE CHEMISTRY
Cartland, Harry E.,Pimentel, George C.
, p. 5485 - 5491 (1986)
The reactions between Hg(3P) atoms with the there dichloroethenes in krypton matrix at 12 K have been studied.In the absence of Hg, matrix photolysis with wavelengths longer than 200 nm gives isomerization as well as, for cis-dichloroethene (c-DCE) and 1,1-dichloroethene (1,1-DCE) but not for trans-dichloroethene (t-DCE), HCl elimination to give ClH.C2HCl.In the presence of Hg atoms and with excitation in the range 246-257 nm, HCl elimination is substantially reduced and, for c-DCE and 1,1-DCE, new products appear.These products are identified as Cl2.C2H2 and chlorovinyl mercuric chlorides, the latter the net result of mercury insertion into a carbon-chloride bond.The insertion product from c-DCE is identified as trans-2-chlorovinyl mercuric chloride and that from 1,1-DCE is probably 1-chlorovinyl mercuric chloride.The results indicate that in the krypton matrix, Hg(3P)-initiated chemistry takes place on a triplet surface that is not accessed with higher energy, singlet excitation.Furthermore, the absence of Cl2 elimination or insertion chemistry for t-DCE indicates that the role of Hg(3P) is not merely energy transfer but, instead, one that opens reaction channels not observed without Hg(3P).
Corrinoid-mediated reduction of tetrachloroethene, trichloroethene, and trichlorofluoroethene in homogeneous aqueous solution: Reaction kinetics and reaction mechanisms
Glod, Guy,Angst, Werner,Holliger, Christof,Schwarzenbach, Rene P.
, p. 253 - 260 (1997)
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.
Electroenzymatic reactions. Investigation of a reductive dehalogenase by means of electrogenerated redox cosubstrates
Diekert, Gabriele,Gugova, Denitsa,Limoges, Benoit,Robert, Marc,Saveant, Jean-Michel
, p. 13583 - 13588 (2005)
As an illustration of how cyclic voltammetry can be used to unravel the mechanisms and kinetics of redox enzymes, the reductive dechlorination of trichloroethylene and tetrachloroethylene by a typical reductive dehalogenase, the tetrachloroethene reductive dehalogenase of Sulfurospirillum multivorans (formerly called Dehalospirillum multivorans), was investigated by means of several electrochemically generated cosubstrates. They comprised the monocation and the neutral form of methylviologen, the neutral form of benzylviologen, and cobaltocene. Cyclic voltammetry is used to produce the active form of the cosubstrate under controlled potential conditions. It shows large plateau-shaped catalytic responses, which are used to measure the kinetics of the enzymatic reaction as a function of the substrate and cosubstrate concentrations. The variation of the rate constant for the cosubstrate reaction with its standard potential shows the transition between two asymptotic behaviors, one in which the reaction is under diffusion control and the other in which it is under counter-diffusion control. Simple fitting of this plot allows an estimation of the standard potential of the electron acceptor center in the enzyme (E° = -0.57 V vs NHE).
Highly efficient Mg(OH)Cl/SiO2 catalysts for selective dehydrochlorination of 1,1,2-trichloroethane
Tang, Cen,Jin, Yanxia,Lu, Jiqing,Li, Xiaonian,Xie, Guanqun,Luo, Mengfei
, p. 10 - 15 (2015)
A series of Mg catalysts supported on SiO2 were prepared by an incipient wetness impregnation method and tested for gas phase dehydrochlorination of 1,1,2-trichloroethane. It was found that these catalysts were very active and selective for the reaction. The catalytic performance depended on the Mg loading rather than the Mg precursors as the catalysts using Mg(NO3)2·6H2O and MgCl2·6H2O as the precursors showed the similar performance. A catalyst containing 10 wt.% of Mg showed the best performance with a steady state TCE conversion of 92% and cis-dichloroethene selectivity of 91%. Moreover, characterizations of the catalysts revealed the formation of Cl-containing Mg species on the surface during the reaction. The analyses of the compositions of the stable catalysts under working conditions indicated a Cl/Mg ratio of 1, suggesting that Mg(OH)Cl could be the active sites for the reaction.
Pathways of chlorinated ethylene and chlorinated acetylene reaction with Zn(O)
Arnold, William A.,Lynn Roberts
, p. 3017 - 3025 (1998)
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.
Isomeric Product Distributions from Solid-State Chain Reactions and Low-Temperature Microexplosions of Acetylene and Chlorine
Ovchinnikov, Mikhail A.,Wight, Charles A.
, p. 5411 - 5414 (1992)
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.
Abiotic reductive dechlorination of chlorinated ethylenes by iron-bearing soil minerals. 1. Pyrite and magnetite
Lee, Woojin,Batchelor, Bill
, p. 5147 - 5154 (2002)
Abiotic reductive dechlorination of chlorinated ethylenes (tetrachloroethylene (PCE), trichloroethylene (TCE), cis- dichloroethylene (cis-DCE), and vinyl chloride (VC)) by pyrite and magnetite was characterized in a batch reactor system. Dechlorination kinetics was adequately described by a modified Langmuir-Hinshelwood model that includes the effect of a decreasing reductive capacity of soil mineral. The kinetic rate constant for the reductive dechlorination of target organics at reactive sites of soil minerals was in the range of 0.185 (±0.023) to 1.71 (±0.06) day-1. The calculated specific reductive capacity of soil minerals for target organics was in the range of 0.33 (±0.02) to 2.26 (±0.06) μM/g and sorption coefficient was in the range of 0.187 (±0.006) to 0.7 (±0.022) mM-1. Surface area-normalized pseudo-first-order initial rate constants for target organics by pyrite were found to be 23.5 to 40.3 times greater than those by magnetite. Target organics were mainly transformed to acetylene and small amount of chlorinated intermediates, which suggests that β-elimination was the main dechlorination pathway. The dechlorination of VC followed a hydrogenolysis pathway to produce ethylene and ethane. The addition of Fe(II) increased the dechlorination rate of cis-DCE and VC in magnetite suspension by nearly a factor of 10. The results obtained in this research provide basic knowledge to better predict the fate of chlorinated ethylenes and to understand the potential of abiotic processes in natural attenuation.
Wood,Dickinson
, p. 3259,3260 (1939)
Determination of Arrhenius parameters for unimolecular reactions of chloroalkanes by IR laser pyrolysis
Dai, Hai-Lung,Specht, Eliot,Berman, Michael R.,Moore, C. Bradley
, p. 4494 - 4506 (1982)
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.
CO2 Laser-induced Decomposition of 1,1,2-Trichloroethane
Ogura, Hiroo
, p. 3528 - 3534 (1985)
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.
Daniels
, p. 2936 (1964)
Reductive Dechlorination of Tetrachloroethylene and Trichlproethylene Catalyzed by Vitamin B12 in Homogeneous and Heterogeneous Systems
Burris, David R.,Delcomyn, Carrie A.,Smith, Mark H.,Lynn Roberts
, p. 3047 - 3052 (1996)
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.
Isotopic fractionation during reductive dechlorination of trichloroethene by zero-valent iron: Influence of surface treatment
Slater,Sherwood Lollar,Allen King,O'Hannesin
, p. 587 - 596 (2002)
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.
Shelf-Stable (E)- A nd (Z)-Vinyl-λ3-chlorane: A Stereospecific Hyper-vinylating Agent
Kanazawa, Junichiro,Miyamoto, Kazunori,Takagi, Taisei,Uchiyama, Masanobu,Watanabe, Yuichiro
, p. 3469 - 3473 (2020)
We report the first stereoselective synthesis of stable (E)- A nd (Z)-β-chlorovinyl-λ3-chlorane via direct mesitylation of 1,2-dichloroethylene with mesityldiazonium tetrakis(pentafluorophenyl)borate under mild reaction conditions. The structure of the (E)-vinyl-λ3-chlorane was established by single-crystal X-ray analysis. Because of the enormously high leaving group ability of the aryl-λ3-chloranyl group, vinyl-λ3-chloranes undergo not only SNVσ-type reaction with extremely weak nucleophiles such as perfluoroalkanesulfonate, iodobenzene, and aromatic hydrocarbons but also coupling with phenylcopper(I) species.
Kinetics of the Tansformation of Trichloroethylene and Tetrachloroethylene by Iron Sulfide
Bulter, Elizabeth C.,Hayes, Kim F.
, p. 2021 - 2027 (1999)
The transformation of trichloroethylene (TCE), tetrachloroethylene (PCE), and 1,1-dichloroethylene (1,1-DCE) by 10 g/L (0.5 m2/L) FeS in aqueous solution at pH 8.3 was studied in batch experiments. TCE and PCE were transformed by FeS with pseudo-first-order rate constants, corrected for partitioning to the sample headspace, of (1.49 +/- 0.14) E-3 h-1 (TCE) and (5.7 +/- 1.0) E-4 h-1 (PGE). A 17 percent decrease in the concentration of 1,1-DCE was observed over 120 days; however, no reaction products were detected. TCE and PCE transformation data were fit to a rate law assuming transformation of TCE via parallel reaction pathways to acetylene and cis-1,2-dichloroethylene (cis-DCE) and transformation of PCE via parallel reaction pathways to acetylene and TCE. Acetylene was the major reaction product for both TCE and PCE. Determination of rate constants for each reaction pathway indicated that TGE was transformed to acetylene 11.8 +/- 1.1 times faster than to cis-DCE and that PCE was transformed to acetylene 8.2 +/-1.8 times faster than to TCE. Additional minor reaction products were vinyl chloride (VC) for TCE and cis-DCE for PCE. Detection of acetylene as the major product of both TCE and PCE transformation by FeS contrasts with the sequential hydrogenolysis products typically observed in the microbial transformation of these compounds, making acetylene a potential indicator of abiotic transformation of TCE and PCE by FeS in natural systems.
Preparation and reactivity of vitaminB12-TiO2 hybrid catalyst immobilized on a glass plate
Shimakoshi, Hisashi,Abiru, Makoto,Kuroiwa, Keita,Kimizuka, Nobuo,Watanabe, Midori,Hisaeda, Yoshio
, p. 170 - 172 (2010)
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.
