28760-99-8Relevant articles and documents
One-Electron Reduction of Ferriporphyrins and Reactions of Ferric and Ferrous Porphyrins with a Halothane-Derived Radical
Brault, D.,Neta, P.
, p. 3405 - 3410 (1982)
The reduction of ferrideuteroporphyrin by α-hydroxyisopropyl radicals is investigated in acidic 2-propanol and acidic 2-propanol-water mixtures by means of steady-state and pulse radiolysis.The rate constant of the reaction is much higher (k ca. 1.3E9 M-1s-1) than that reported for neutral solutions emphasizing the effect of the positive charge carried by the ferric porphyrin in acidic solutions (due to protonation of the alkoxide ligand).Competition kinetic experiments using p-nitroacetophenone as a reference solute show that α-hydroxyisopropyl radicals are readily scavenged by halothane (CF3CHClBr), leading to radicals.Pulse irradiation of ferriporphyrin solutions containing halothane allows investigation of the reaction of radicals with either ferric or ferrous porphyrins depending on the halothane concentration.No reaction of radicals with ferriporphyrin can be detected (k -1s-1).On the other hand, a nearly diffusion-controlled reaction is observed between radicals and ferrous porphyrin leading to the ?-bonded alkyl complex of the ferric porphyrin (PFeIIICF3CHCl, where CF3CHCl stands for the alkyl anion).These results are discussed with regard to the reactivity of other alkyl radicals.The relevance to biological models of toxicity of halothane (a widely used anesthetic agent) is outlined.
Kinetics of the Reaction of OH Radicals with CH2ClCF2Cl and CH2ClCF3 over an Extended Temperature Range
Fang, Tunchen D.,Taylor, Philip H.,Berry, Rajiv J.
, p. 2700 - 2704 (1999)
Rate coefficients are reported for the gas-phase reaction of hydroxyl (OH) radicals with CH2ClCF2C1 (k1) and CH2ClCF3 (k2) over an extended temperature range. The measurements were performed using a laser photolysis/laser-induced fluorescence (PLP/LIF) technique under slow flow conditions at a total pressure of 740 ±10 Torr. The lower temperature measurements for k1 were in agreement with previous measurements using different techniques. Prior measurements for k2 using different techniques exhibit significant scatter. The new lower temperature data reported here lie intermediate to the previous measurements. Arrhenius plots of the data exhibit significant curvature and were fit to the expression k(T) = ATB exp(-C/T). A semiempirical fitting approach was used in which A and B were obtained from transition-state theory (TST) and C was determined from a nonlinear least-squares fit to the experimental data. Ab initio calculations were used to evaluate the thermochemical properties of the activated complex. The resulting modified Arrhenius expressions were k1(295-788 K) = (8.53 ± 4.06) × 10-19T2.28 ± 0.18 exp[(-937 ± 296)/T] cm3 molecule-1 s-1 and k2(295-866 K) = (3.06 ± 4.02) × 10-18T1.91± 0.03 exp[(-644 ± 313)/T] cm3 molecule-1 s-1. Error limits are ± 2σ. The TST-based modified Arrhenius expression is compared to previous TST and SAR predictions. The effect of halogen substitution on the reactivity of these compounds is briefly discussed. The incorporation of a Wigner tunneling factor and its impact on the TST fit of the data is also presented and discussed.
Experimental Studies of Ozone Depletion by Chlorofluorocarbons (CFC's), Bromofluorocarbons (BFC's), Hydrochlorofluorocarbons (HCFC's), and CH3Br Using a 6-m3 Photochemical Chamber
Washida, Nobuaki,Imamura, Takashi,Bandow, Hiroshi
, p. 535 - 541 (1996)
Ozone destruction by CFC's (CFCl3 and CF2Cl2), BFC's (CF3Br and C2F4Br2), HCFC's (CH3CCl2F, CF3CHCl2, and CF3CHFCl), and CH3Br was demonstrated using a 6-m3 evacuable photochemical chamber equipped with UV-enhanced Xe arc lamps. The decay of ozone by a catalytic cycle involving Cl or Br atoms released from the photolysis of halocarbons by UV light was evident, although the chain length was far less than that in the real stratosphere: It was about 8 for CFCl3 and 40 for CF3Br. The rates of ozone decomposition were faster in the BFC's than in the CFC's. According to a box-model simulation, in the CFCl3 system 90% of the catalytic cycle proceeds from reactions of Cl+O3→ClO+O2 and ClO+O→Cl+O2. On the other hand, in the CF3Br system 90% of the catalytic cycle is governed by the following reactions: Br+O3→BrO+O2 and BrO+BrO→2Br+O2. The HCFC's and CH3Br can destroy the ozone with sufficient potential as CFC's and BFC's when they enter the stratosphere.
Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons
Sousa, Sonia R.,Bialkowski, Stephen E.
, p. 3871 - 3878 (1997)
The relative electron capture detector (ECD) response to alternative fluorocarbons (AFCs) using gas chromatography are found to be at least 1 order of magnitude lower than that for CFC-12. Detection limits for the chlorofluorocarbons CFC-12, HCFC-22, HCFC-123, and HCFC-124 are found to be 2.5, 90, 30, and 90 pg, respectively. Those for the hydrofluorocarbons are significantly poorer; 14 and 45 ng for HFC-125 and HFC-134a, respectively. HFC-152a was not detected using ECD. Since atmospheric concentrations of these compounds are in the low part-per-trillion level, GC-ECD is apparently not sensitive enough to be used for AFC analysis without substantial preconcentration. Two columns are evaluated for the AFC separation. The Poraplot Q WPLOT column showed good separation ability, though column bleed limits detection performance. A Carboxen 1004 packed column exhibits much lower interference. But separations are time consuming and peak broadening adversely affects limits of detection. Mechanisms for the ECD response are proposed based on thermodynamics and temperature-dependent ECD responses. CFC-12, HCFC-123, and HFC-125 apparently undergo ion-forming dissociative electron capture. The electron capture process for HCFC-22 and HFC-134a appear to form molecular ions. Both mechanisms appear to be operative for HCFC-124 electron capture. Dissociative electron capture rate constants for HCFC-123, HCFC-124, and HFC-125 are estimated to be 3.5 × 10-10, 1.0 × 10-10, and 5.6 × 10-13 cm3 s-1, respectively at 300 °C.
FTIR spectroscopic study of 1,1,1-trifluoro-2-chloroethyl and 1,1,1- trifluoro-2-chloroethylperoxyl radicals
Baskir,Korolev,Nefedov
, p. 519 - 522 (2007/10/03)
A combination of matrix isolation and FTIR spectroscopy was applied to investigate 1,1,1-trifluoro-2-chloroethyl (1) and 1,1,1-trifluoro-2- chloroethylperoxyl (2) radicals. Radical 2 was obtained by vacuum pyrolysis of 1,1,1-trifluoro-2-bromo-2-chloroethane (3). Corresponding peroxyl radicals was generated by co-condensation of pyrolysis products and molecular oxygen in an argon matrix. To assign the experimental bands DFT calculations (B3LYP/6-311G**) were carried out. The fundamental bands of O-O and C-O stretching vibrations of peroxyl radical CF3CHClOO (1102.1, 972.7, cm-1) were identified by their red shifts to 1044.7 and 954.1 cm-1 in the spectra of 18O substituted derivatives. UV photolysis of the radical 2 in the low- temperature matrix produced difluoroformaldehyde CF2O, radicals ClCO, CF3, as well as CO and HCl as the primary photoproducts.
Atmospheric Chemistry of HCFC-133a: The UV Absorption Spectra of CF3CClH and CF3CClHO2 Radicals, Reactions of CF3CClHO2 with NO and NO2, and Fate of CF3CClHO Radicals
Moegelberg, Trine E.,Nielsen, Ole J.,Sehested, Jens,Wallington, Timothy J.
, p. 13437 - 13444 (2007/10/02)
The UV absorption spectra of CF3CClH and CF3CClHO2 radicals have been investigated.The CF3CClH spectrum was quantified over the wavelenght range 225-280 nm.The absorption cross section at 250 nm was (139+/-16)*10-20 cm2 molecule-1.The absorption spectrum for CF3CClHO2 was quantified over the wavelength range 225-290 nm, and at 250 nm ?250nm=(258+/-30)*10-20 cm2 molecule-1.The kinetics of the reactions of the peroxy radical CF3CClHO2 with NO and NO2 were studied and the derived rate constants were k3=(1.0+/-0.3)*10-11 cm3 molecule-1 s-1 and k4=(6.4+/-1.5)*10-12 cm3 molecule-1 s-1, respectively.The self-reaction rate for the CF3CClHO2 radicals were measured and a value of k6obs=(4.4+/-0.3)*10-12 cm3 molecule-1 s-1 was obtained.The reactions of F atoms with CF3CH2Cl and of CF3CClH with O2 were found to proceed with rate constants of k8=(2.0+/-0.6)*10-12 cm3 molecule-1 s-1 and k2=(1.4+/-0.1)*10-12 cm3 molecule-1 s-1, respectively.The reaction of CF3CClHO2 radicals with NO gives NO2, and by implication CF3CClHO radicals, which in the atmosphere (a) react with O2 to give CF3C(O)Cl and (b) decompse to give, most likely, CF3 radicals and HC(O)Cl.In 700 Torr of N2 diluent the rate constant ratio kO2/Kdiss=(2.1+/-0.4)*10-19 cm3 molecule-1.As part of the present work, relative rate techniques were used to measure rate constants for the reactions of Cl and F atoms with CF3CH2Cl of (6.8+/-1.2)*10-15 and (2.1+/-0.5)*10-12 cm3 molecule-1 s-1, respectively.All experiments were performed at 296+/-2 K.
Electron Transfer Reactions of Halothane-derived Peroxyl Free Radicals, CF3CHClO2.: Measurement of Absolute Rate Constants by Pulse Radiolysis
Moenig, Joerg,Asmus, Klaus-Dieter,Schaeffer, Michel,Slater, Trevor F.,Willson, Robin L.
, p. 1133 - 1138 (2007/10/02)
The halothane-derived peroxyl radical CF3CHClO2. has been generated in aqueous solutions by pulse radiolysis.Absolute rate constants for the reduction of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) by hydrated electrons, hydrogen atoms, and propan-2-ol free radicals have been determined to be k 1.4E10, 3.8E8, and 7.6E7 l mol-1 s-1, respectively.The predominant product radical CF3CHCl rapidly adds O2, and an estimate of k 1.3E9 l mol-1 s-1, has been obtained for the absolute rate constant of this reaction.The resulting peroxyl radical CF3CHClO2. has been found to react rapidly with a variety of nucleophilic compounds such as 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate), the phenothiazines promethazine, chlorpromazine, and metiazinic acid, the vitamins C and E, and propyl gallate.The absolute rate constants for these reactions are found to be generally lower than for corresponding reactions of the carbon tetrachloride-derived radical, CCl3O2..
