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).
Factors influencing rates and products in the transformation of trichloroethylene by iron sulfide and iron metal
Butler, Elizabeth C.,Hayes, Kim F.
, p. 3884 - 3891 (2001)
Batch experiments were performed to assess (i) the influence of pH, solution amendments, and mineral aging on the rates and products of trichloroethylene (TCE) transformation by iron sulfide (FeS) and (ii) the influence of pretreatment of iron metal with NaHs on TCE transformation rates. The relative rates of FeS-mediated transformation of TCE to different products were quantified by branching ratios. Both pseudo-first-order rate constants and branching ratios for TCE transformation by FeS were significantly influenced by pH, possibly due to a decrease in the reduction potential of reactive surface species with increasing pH. Neither Mn2+, expected to adsorb to FeS surface S atoms, nor 2,2′-bipyridine, expected to adsorb to surface Fe atoms, significantly influenced rate constants or branching ratios. FeS that had been aged at 76 °C for 3 days was completely unreactive with respect to TCE over 6.5 months, yet this aged FeS transformed hexachloroethane to tetrachloroethylene with a rate constant only slightly lower than that for nonaged FeS. This finding suggests that the oxidation state of iron sulfide minerals in the environment will strongly influence the potential for intrinsic remediation of pollutants such as TCE. Treatment of iron metal with bisulfide significantly increased the pseudo-first-order rate constant for TCE transformation at pH 8.3. This effect was attributed to formation of a reactive FeS coating or precipitate on the iron surface.
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).
FTIR Study of the Cl + C2H2 Reaction: Formation of cis- and trans-CHCl=CH Radicals
Zhu, T.,Yarwood, G.,Chen, J.,Niki, H.
, p. 5065 - 5067 (1994)
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.
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.
CO2 Laser-induced Decomposition of 1,2-Dichloro-1-fluoroethane
Ogura, Hiroo,Yano, Takayuki
, p. 1239 - 1250 (1985)
CH2ClCHFCl was photolyzed with a TEA CO2 laser at 1033.5 cm-1.The infrared multiphoton dissociation mechanism of CH2ClCHFCl was investigated under various conditions: Sample gas pressure, additive gas presure, pulse number, pulse energy, and pulse duration.It is concluded that primary process of the IRMPD is direct eleimination of molecular HCl and HF, HCl elimination being predominant channel.Primary HCl elimination products cis-and trans-CHF=CHCl, and CH2=CFCl are formed at high vibrational levels, from which additional photon absorption occures in the secondary photolysis to give rise to CH=CCl, CH=CF, and CH2=CHF.All of the secondary products are concluded to be derived from mainly CH2=CFCl among the chlorofluoroethene isomers.CH2=CFCl decomposes via HF and HCl elimination channels together with the C-Cl bond repture channel. appears to be generated by the H atom abstraction reaction of C2H. radical, which may result from further decomposition of and/or .The neat IRMPD at higher pressures gives quite similar primary product distribution, but markedly different secondary product distribution from those in shock tube pyrolysis.
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.
Pd-catalyzed TCE dechlorination in water: Effect of [H2](aq) and H2-utilizing competitive solutes on the TCE dechlorination rate and product distribution
Reinhard,Lowry
, p. 696 - 702 (2001)
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
