COMMUNICATIONS TO THE EDITOR
Nov. 5, 1956 CHs CH,
+ isooctane +CHI + isooctyl radical
+ olefin +olefinCH8
k1
4,
- E1 - E1
= -0.6 kcal./mole
A ~ / A I= 13.0
= -2.8 kcal./mole
A2/A1 = 5.3
The reactivity of tetrachloroethylene is too low to determine the activation energy with any reasonable accuracy. We conclude t h a t the reactivity of tetrafluoroethylene is approximately ten times greater than t h a t of ethylene, while tetrachloroethylene is unreactive. The higher reactivity of tetrafluoroethylene is shown to result from the lower activation energy of the addition reaction (as compared with ethylene), while the AZ/A1 factor is lower for the reaction involving tetrafluoroethylene than that for ethylene. The methyl affinity of ethylene is comparable to that of vinylacetate, is approximately 80 times greater than t h a t of benzene and l / 2 6 as large as that of styrene. TABLEI Compound
T, ‘C.
kdki
Ethylene Ethylene Ethylene Ethylene Tetrafluoroethylene Tetrafluoroethylene Tetrafluoroethylene Tetrafluoroethylene Tetrachloroethylene
54.7 64.9 74.8 85.2 54.7 64.9 74.8 85.2 64.9
37 3 f 0.6 34.1 f 2 . 2 34.6 f 0.6: 35.5 f 1 . 5 400 f 7 342 f 14 307 rt 8 273 f 8
