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An ab Initio Study of the Kinetics of the Reactions of Halomethanes with the Hydroxyl Radical. 3. Kinetic Parameters Predictions for the Potential Halon Replacements CH2FBr, CHFBr2, CHFClBr, CHCl2Br, and CHClBr2

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journal contribution
posted on 16.12.2000, 00:00 by Florent Louis, Carlos A. Gonzalez, Robert E. Huie, Michael J. Kurylo
Ab initio PMP4(SDTQ)/6-311G(3df,2p)//MP2/6-311G(2d,2p) calculations, together with canonical transition state theory, were used in order to compute the energetics and predict the kinetics (in the temperature range 250−400 K) of the H atom abstraction reaction between the hydroxyl radical and the five halomethanes:  CH2FBr, CHFBr2, CHFClBr, CHCl2Br, and CHClBr2. The procedure adopted in this study has been discussed and validated in our previous two publications (Louis, F.; Gonzalez, C. A.; Huie, R. E.; Kurylo, M. J. J. Phys. Chem. A 2000, 104, 2931. Louis, F.; Gonzalez, C. A.; Huie, R. E.; Kurylo, M. J. J. Phys. Chem. A 2000, 104, 8773.). In the present work, this computational procedure is extended to develop relations of the Evans−Polanyi type, which provide an alternate method to predict rate constants for other reactions where computational expense becomes a limiting factor. In addition, rate constants computed at 277 K were used in the estimation of the atmospheric lifetimes for the five halomethanes. The validity of these results is also discussed.

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