Experimental Studies of Ozone Depletion by Chlorofluorocarbons (CFC’s), Bromofluorocarbons (BFC’s), Hydrochlorofluorocarbons (HCFC’s), and CH<sub>3</sub>Br Using a 6-m<sup>3</sup>Photochemical Chamber
作者:Nobuaki Washida、Takashi Imamura、Hiroshi Bandow
DOI:10.1246/bcsj.69.535
日期:1996.3
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
Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons
作者:Sonia R. Sousa、Stephen E. Bialkowski
DOI:10.1021/ac9703921
日期:1997.10.1
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 electroncapture. The electroncapture process for HCFC-22 and HFC-134a appear to form molecular ions. Both mechanisms appear to be operative for HCFC-124 electroncapture. Dissociative electroncapture rate constants for
Moenig, Joerg; Asmus, Klaus-Dieter; Schaeffer, Michel, Journal of the Chemical Society. Perkin transactions II, 1983, p. 1133 - 1138
作者:Moenig, Joerg、Asmus, Klaus-Dieter、Schaeffer, Michel、Slater, Trevor F.、Willson, Robin L.
DOI:——
日期:——
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
作者:Trine E. M.danisho.gelberg、Ole J. Nielsen、Jens Sehested、Timothy J. Wallington
DOI:10.1021/j100036a018
日期:1995.9
Kinetics of the Reaction of OH Radicals with CH<sub>2</sub>ClCF<sub>2</sub>Cl and CH<sub>2</sub>ClCF<sub>3</sub> over an Extended Temperature Range
作者:Tunchen D. Fang、Philip H. Taylor、Rajiv J. Berry
DOI:10.1021/jp984273g
日期:1999.4.1
Rate coefficients are reported for the gas-phase reaction of hydroxyl (OH) radicals with CH2ClCF2Cl (k(1)) and CH2ClCF3 (k(2)) 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 k(1) were in agreement with previous measurements using different techniques. Prior measurements for k(2) 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) = AT(B) 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 k(1)(295-788 K) = (8.53 +/- 4.06) x 10(-19)T(2.28+/-0.18) exp[(-937 +/- 296)/T] cm(3) molecule(-1) s(-1) and k(2)(295-866 K) = (3.06 +/- 4.02) x 10(-18)T(1.91+/-0.03) exp[(-644 +/- 313)/T] cm(3) molecule(-1) s(-1). Error limits are +/-2 sigma. The TST-based modified Arrhenius expression is compared lo 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.