The kinetics of the thermal decomposition of trifluoroacetaldehyde

Abstract

The thermal decomposition of trifluoroacetaldehyde has been studied at temperatures between 471� and 519�, and at pressures up to 180 mm. The main products of reaction are trifluoromethane and carbon monoxide in equal amounts; small amounts of hexafluoroethane and hydrogen are also formed. The experimental rate equation governing the observed kinetics is of the form Rate = k?[CF3CHO]3/2, where k? = 1012.2exp(-49000/RT) l.� mole-1 sec-1 A small surface effect is apparent, an increase in surface area causing an increase in rate. Inert gases, namely carbon monoxide and dioxide, increase the rate of decomposition, the experimental rate equation assuming the form Rate = (k'[CF3CHO]3 + k"[CF3CHO]2.2[M])� A mechanism is proposed which predict,^ the experimental form of the rate equation and involves initiation through a second-order energy transfer process followed by a radical chain mechanism, the length of which is 1200 with P(CF3CHO) = 200 mm. Termination is considered to be through the third-order recombination of trifluoromethyl radicals.