Atmospheric chemistry of 1,1,1,2-tetrachloroethane (CCl₃CH₂Cl): Spectrokinetic investigation of the CCl₃CClHO₂ radical, its reactions with NO and NO₂, and atmospheric fate of the CCl₃CClHO radical

A pulse radiolysis technique was used to study the ultraviolet absorption spectra of CCl3CClH and CCl3-CClHO2 radicals, the kinetics of the self-reaction of CCl3CClHO2 radicals, and the kinetics of the reactions of CCl3CClHO2 with NO and NO2 in the gas phase at 296 K. At 240 nm, σ(CCl3CClH) = (303 ± 35) × 10-20, and at 250 nm, σ(CCl3CClHO2) = (288 ± 48) × 10-20 cm2 molecule-1.

The observed rate constant for the self-reaction of CCl3CClHO2 radicals was (5.0 ± 1.2) × 10-12 cm3 molecule-1 s-1. The rate constants for reactions of CCl3CClHO2 radicals with NO and NO2 were k3 > 9.0 × 10-12 and k4 = (8.9 ± 2.6) × 10-12 cm3 molecule-1 s-1, respectively. A long path length Fourier transform infrared technique was used to show that at 295 K in 700 Torr total pressure of air 76 ± 3% of CCl3CClHO radicals decornpose via C-C bond scission and 24 ± 3% undergo three-center intramolecular HCl elimination.

As part of this work rate constants for the reaction of F and Cl atoms with CCl3CH2Cl were determined to be (6.4 ± 1.2) × 10-12 and (5.7 ± 1.0) × 10-14 cm3 molecule-1 s-1, respectively. The results are discussed with respect to the atmospheric chemistry of tetrachloroethane.