SUBSTITUENT EFFECTS ON THE DISPROPORTIONATION-COMBINATION RATE-CONSTANT RATIOS FOR GAS-PHASE HALOCARBON RADICALS .2. REACTIONS OF CENTER-DOT-CF3-CENTER-DOT AND 3CH2CH2-CENTER-DOT+CF3CH2CH2-CENTER-DOT(CF3CH2CH2)

Disproportionation/combination rate constant ratios, k(d)/k(c), have b een measured for the collision between CF3CH2CH2 and CF3 radicals to b e 0.022 +/- 0.002 and for CF3CH2CH2 and CF3CH2CH2 radicals to be 0.100 +/- 0.002. Comparison to previous work from this laboratory for the r eaction of CF3CH2CHCl with CF3 radicals shows that substitution of Cl for H increases the k(d)/k(c) by about 50%; however, for the auto disp roportionation-combination of CF3CH2CH2 radicals the chlorine substitu ent decreases the observed rate constant ratio by a factor of two. The chlorine substituent effect on the observed k(d)/k(c) ratios is compa red to predictions from molecular orbital calculations. (C) 1996 John Wiley & Sons, Inc.