Rate constants for the reaction of OH radicals with CHF2Cl, CF2Cl2, CFCl3, and H2 over the temperature range 297–434 °K

Abstract

Rate constants for the reaction of OH radicals with CHF2Cl, CF2Cl2, CFCl3, and H2 have been determined over the temperature range 297–434 °K using a flash photolysis–resonance fluorescence technique. The following Arrhenius expressions were obtained: k1(CHF2Cl) =1.21×10−12e−(3250±300)/RT cm3 molecule−1 sec−1, k1(CF2Cl2) <1×10−15 cm3 molecule−1 sec−1 (T=297–424 °K), k1(CFCl3) <1×10−15 cm3 molecule−1 sec−1 (T=297–424 °K), k1(H2) =5.9×10−12 e−(3990±300)/RT cm3 molecule−1 sec−1. The rate constants for the reaction of OH radicals with H2, which were used to check the experimental system, are in good agreement with literature values. The atmospheric significance of the reaction of OH radicals with CHF2Cl is briefly discussed.

Absolute Rate Measurements of the Reaction of OH Radicals with HCFC-21 (CHFCl2) and HCFC-22 (CHF2Cl) over an Extended Temperature Range

“…Also shown are previous measurements reported using different techniques. The various techniques include (1) discharge flow−laser magnetic resonance spectroscopy (DF-LMR), (2) flash photolysis−resonance fluorescence spectroscopy (FP-RF), , (3) flash photolysis−resonance absorption spectroscopy (FP-RA), , (4) discharge flow−resonance fluorescence spectroscopy (DF-RF), − and (5) pulse radiolysis−resonance absorption spectroscopy (PR-RA) . With the exception of Clyne and Holt, our overlapping rate measurements are in reasonably good agreement with previous measurements.…”

“…For the successful modeling of their combustion, accurate semiempirical Arrhenius parameters describing the rate behavior over extended temperature ranges are required. Previous measurements have only been reported over a limited temperature range encompassing tropospheric and stratospheric conditions. − At temperatures above 480 K, the prediction of rate constants has been based solely on semiempirical transition state theory (TST) , and structure-active relationship (SAR) calculations . Rate coefficient measurements over an extended temperature range are needed to verify and/or refine previously published TST and SAR models.…”

The features of combustion of hydrogen and methane in oxygen and air in the presence of difluorodichloromethane additives

“…In [29] an estimate of the reaction rate constant is given (in [30], however, it is claimed that this reaction practically does not occur)…”

Chemistry of Stratospheric Chlorine

“…The reactions with O(1D) and OH are found to be negligible in the stratosphere on the basis of the kinetic data from Pitts et al (1974), Jayanty et al (1975a, b), Davis (1975), Atkinson et al (1975), Howard and Evenson (1976), and Cox et al (1976). These reactions also operate in the troposphere, though very slowly; they must be rare sinks of the chlorocarbons in the troposphere like the destructions by lightning discharge and by reactions with ions.…”