The addition of methyl radicals to tetrafluoroethylene

Abstract

The addition of methyl radicals to tetrafluoroethylene in the gas phase has been studied over the temperature range 8O-18O0C, using a material balance method.CH, + C,F4 -+ CH,C,F, Arrhenius parameters of 1011.95*0.23 (mole-l cm3 sec-l) and 5.7 f 0.4 (kcal/mole) have been measured for the addition reaction.Electrophilic reagents such as 0 or CF, appear to react almost equally readily with ethylene and tetrafluoroethylene but methyl radicals add much more rapidly to tetrafluoroethylene than to ethylene, the difference in reactivity being principally due to an activation energy difference of -2 kcal/mole.The addition of methyl radicals to a variety of olefins has been studied by several workers [ 1-41, in general methods involving either mass-balance relationships or reaction product analysis being used. Recently, Cvetanovic and Irwin [5] have developed a technique based on the methane deficiency to study such reactions; this involves the use of small amounts of biacetyl as the methyl radical source in the presence of large concentrations of a reference hydrocarbon (isobutane) and the olefin. Determination of the carbon monoxide and methane yields at different olefin/hydrocarbon ratios enables a rate constant to be deduced for the addition reaction.No study of the reaction of methyl radicals with tetrafluoroethylene has been reported and accordingly we have applied Cvetanovic's technique to the study of this addition reaction in the temperature range 80-180°C. I t is clearly of interest to compare the methyl radical addition data with those for the analogous reaction involving trifluoromethyl radicals. Szwarc [6] has studied the latter reaction using a competitive technique in which abstraction of hydrogen from 2,3-dimethylbutane was the competing reaction so that values of A l / A , and El -E, are known.

Some hydrogen abstraction reactions of the trichloromethyl radical

“…"Ref. [9]. n-hexane used in this study, this difference cannot be attributed to structural or polar effects.…”