HYDROGEN-ATOM ATTACK ON 1,2-DICHLOROTETRAFLUOROETHANE - RATES OF HALOGEN ABSTRACTION

Hydrogen atom attack on 1,2-dichlorotetrafluoroethane (DCFE) at temper atures between 970 and 1140 K and pressures of about 200-500 kPa (2-5 bar) has been studied with a single-pulse shock tube reactor. The obse rved products show that chlorine is readily abstracted, while fluorine is removed in at most trace quantities only. This is despite the grea ter exothermicity of the fluorine abstraction channel. Relative to the standard reaction of displacement of methyl from 1,3,5-trimethylbenze ne, for which k[H + (CH3)(3)C6H3 --> (CH3)(2)C6H4 + CH3] = 6.7 x 10(13 ) exp(-3255/T) cm(3) mol(-1) s(-1), k(H + DCFE --> CF2CF2Cl + HCl) = 2 .1 x 10(14) exp(-5839/T) cm(3) mol(-1) s(-1) and k(H + DCFE --> CFClCF 2Cl + HF, 1100 K) less than or equal to 7 x 10(9) cm(3) mol(-1) s(-1). Uncertainties are estimated to be factors of 1.1 and 1.4 on relative and absolute bases, respectively. Comparisons with relevant literature data are made. The slow rate of F abstraction implies that reaction o f fluorinated compounds via this pathway will be unimportant except in compounds unable to react via other channels. Implications with regar d to the destruction of fluorinated compounds in pyrolytic and combust ion systems are discussed.