Trine E. Møgelberg

Atmospheric chemistry of CF3COOH. Kinetics of the reaction with OH radicals

Abstract Two different experimental techniques were used to study the kinetics of the reaction of OH radicals with trifluoroacetic acid, CF3COOH. Using a pulse radiolysis absolute rate technique, rate constants at 315 and 348 K were determined to be (1.6±0.4)×10−13 and (1.5±0.2)×10−13 cm3 molecule−1 s−1, respectively. Using a long path-length FTIR relative rate technique a rate constant of (1.7±0.5)×10−13 cm3 molecule−1 s−1 was obtained at 296 K. In the atmosphere, reaction with OH radicals in the gas phase is estimated to account for 10%–20% of the loss of CF3COOH. The major fate of CF3COOH is rainout.

Atmospheric chemistry of 1,4-dioxane

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C 4 H 7 O 2 and (c-C 4 H 7 O 2 )O 2 radicals over the range 220–320 nm, σ(c-C 4 H 7 O 2 ) 250nm = (5.9 ± 0.6) × 10 −18 and σ[(c-C 4 H 7 O 2 )O 2 ] 240nm = (4.8 ± 0.8) × 10 −18 cm 2 molecule −1 . The observed self-reaction rate constants for the c-C 4 H 7 O 2 and (c-C 4 H 7 O 2 )O 2 radicals, defined as −d[c-C 4 H 7 O 2 ]/dt = 2k 4 [c- C 4 H 7 O 2 ] 2 and −d[(c-C 4 H 7 O 2 )O 2 ]/dt = 2k 5obs [(c-C 4 H 7 O 2 )O 2 ] 2 were k 4 = (3.3 ± 0.4) × 10 −11 and k 5obs = (7.3 ± 1.2) × 10 −1 2 cm 3 molecule −1 s −1 . The rate constants for reactions of (c-C 4 H 7 O 2 )O 2 radicals with NO and NO 2 were k 6 (1.2 ± 0.3) × 10 −11 and k 7 = (1.3 ± 0.3) × 10 −11 cm 3 molecule −1 s −1 , respectively. The rate constants for the reaction of F atoms with 1,4-dioxane and the reaction of c-C 4 H 7 O 2 radicals with O 2 , were k 3 = (2.4 ± 0.7) × 10 −10 and k 2 = (8.8 ± 0.9) × 10 −12 cm 3 molecule −1 s −1 , respectively. A relative rate technique was used to measure the rate constant for the reaction of Cl atoms with 1,4-dioxane, k 17 = (2.0 ± 0.3) × 10 −10 cm 3 molecule −1 s −1 . A long-pathlength FTIR spectrometer coupled to a smog chamber system was used to show that the sole atmospheric fate of the alkoxy radical (c-C 4 H 7 O 2 )O is decomposition via C–C bond scission leading to the formation of H(O)COCH 2 CH 2 OC(O)H (ethylene glycol diformate).

Atmospheric chemistry of HFC‐134a: Kinetics of the decomposition of the alkoxy radical CF3CFHO

Decomposition of the CF3CFHO radical formed in the reaction of CF3CFHO2 radicals with NO was studied at 296 and 393 K using a pulse radiolysis transient VIS-UV absorption absolute rate technique. At room temperature in 1 atmosphere of SF6 diluent it was found that the majority (79 ± 20)% of CF3CFHO radicals formed in the CF3CFHO2 + NO reaction decompose within 3 μs via C(SINGLE BOND)C bond scission. This result is discussed with respect to the current understanding of the atmospheric degradation of HFC-134a. As a part of the present work the rate constant ratio kCF3CFH+02/kCF3CFH+NO was determined to be 0.144 ± 0.029 in one atmosphere of SF6 diluent at 296 K.

Atmospheric chemistry of HFC-134a. Kinetic and mechanistic study of the CF3CFHO2+NO2 reaction

Abstract A pulse radiolysis system was used to study the kinetics of the reaction of CF 3 CFHO 2 with NO 2 . By monitoring the rate of the decay of NO 2 using its absorption at 400 nm the reaction rate constant was determined to be k =(5.0±0.5)×10 −12 cm 3 molecule −1 s −1 . A long path length Fourier-transform infrared technique was used to investigate the thermal decomposition of the product CF 3 CFHO 2 NO 2 . At 296 K in the presence of 700 Torr of air, decomposition of CF 3 CFHO 2 NO 2 was rapid (greater than 90% decomposition within 3 min). The results are discussed in the context of atmospheric chemistry of CF 3 CFH 2 (HFC-134a).