Rate Constants for the Reactions of OH Radicals with CH₃OCF₂CHF₂, CHF₂OCH₂CF₂CHF₂, CHF₂OCH₂CF₂CF₃, and CF₃CH₂OCF₂CHF₂ over the Temperature Range 250−430 K

Abstract

The OH reaction rate constants have been measured for CH3OCF2CHF2, CHF2OCH2CF2CHF2, CHF2OCH2CF2CF3, and CF3CH2OCF2CHF2 over the temperature range 250−430 K. Kinetic measurements have been carried out using the flash photolysis, laser photolysis, and discharge flow methods, combined respectively with the laser-induced fluorescence technique to monitor the OH radical concentrations. The influence of impurities contained in the samples of fluorinated ethers has been investigated by means of sample purification using gas chromatography. No sizable effect of impurities was found on the measured rate constants of these fluorinated ethers, if the purified samples were used in the kinetic measurements. The Arrhenius rate constants have been determined from the respective kinetic data as k(CH3OCF2CHF2) = 2.60 × 10-12 exp[−(1420 ± 170)/T], k(CHF2OCH2CF2CHF2) = 2.49 × 10-12 exp[−(1500 ± 170)/T], k(CHF2OCH2CF2CF3) = 2.14 × 10-12 exp[−(1580 ± 170)/T], and k(CF3CH2OCF2CHF2) = 1.49 × 10-12 exp[−(1520 ± 170)/T] cm3 molecule-1 s-1, where the quoted errors represent the 95% confidence level and included systematic errors. Uncertainty factors at 298 K (with the formulation of the NASA panel for data evaluation14) for these fluorinated ethers were 1.1.

Rate constants for the gas‐phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250–430 K

“…The OH decay shows exponential behavior, and for all experiments, the scatter of the points for individual decay plots is much the same as that in Fig. 1 (3)(4)(5).…”

“…In the troposphere, the H-abstraction reaction by OH radicals is expected to be the dominant process for destruction of CF 3 The rate constants for reactions of organic compounds with OH radicals can be measured by either absolute rate methods or relative rate methods [2]. Absolute rate methods have the advantage of giving absolute rate constants based on observations of the rate of loss of OH radicals in the presence of the organic compounds, but the experimentally determined values of the absolute rate constants are easily affected by the loss of OH radicals through interaction with reactive impurities or secondary products [3,4]. Relative rate methods involve monitoring changes in the ratios of the sample and a reference compound, and are insensitive to impurities in the samples [3,5].…”

Kinetic study of the gas‐phase reaction of hydroxyl radical with CF3CH2OCH2CF3 using the laser photolysis–laser induced fluorescence method

“…Owing to limitations of the present experimental setup, the measurement of the rate coefficient at this temperature was not possible. However, the present data in 298-365 K range can be extrapolated to 272 K because the Arrhenius plot is linear in 270-400 K range for all the fluoroethers reported so far [5,6,9]. The rate coefficient of TFEE at 272 K, thus calculated from this work, is found to be 1.02 × 10 −13 cm 3 molecule −1 s −1 , very close to 9.55 × 10 −14 cm 3 molecule −1 s −1 calculated using the kinetic parameters of [9].…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…The room temperature result of Zhang et al [1526] lies significantly higher than the recommended value, possibly due to the presence of reactive impurities in the sample. (Table: The recommended parameters were derived from a fit to the data (below 400 K) of Tokuhashi et al [1313] (two independent absolute measurement studies). (Table: 02-25, Note: 02-25) Back to Table E48.…”

“…OH + CHF 2 OCH 2 CF 2 CF 3 . The recommended parameters were derived from a fit to the data (below 400 K) of Tokuhashi et al [1313] (two independent absolute measurement studies). (Table: 02-25, Note: 02-25) Back to Table E49.…”