Mixtures of 1,1,3,3-tetrafluoroacetone and perf luorodi-n-propyl ketone have been photolyzed together over the temperature range 50" to 200"C, and the disproportionation/combination ratio for n-C3F7 and CFzH radicals has been determined to be A(n-CsF7, CFZH) = 0.072 ? 0.003. A reevaluation of existing data on CH3 and CFzH radicals leads to a value of A(CH3, CFzH) = 0.35. The large variations in A for the reactions of alkyl and perfluoroalkyl radicals with CFzH radicals are discussed. 0 1992 John Wiley & Sons, Inc.

Cross-disproportionation to combination ratios for CF2H and n-C3H7 radicals have been determined (the hydrogen acceptor radical is given first) to be A(n-C3H7,CF2H) = 0.30 2 0.01 and A(CF2H, n-C3H7) = 0.057 ? 0.006.

Disproportionation Reactions Between Alkyl and Fluoroalkyl Radicals. Part 7. Difluoromethyl with Perfluoro-n-propyl and Methyl Radicals -(photolysis of CF2H-CO-CF2H/C3F7-CO-C3F7 mixtures over a temp. range between 50 and 200 • C). -(PRITCHARD, G. O.; FOLLMER, D. W.; MELEASON, M. A.; SHOEMAKER, D. D.; PERKINS, J. C.; LEUPP, S. L.; Int.

A redetermination of the disproportionation/combination ratio for n-CsF7 and CzH5 radicals gives a value of A(n-C3F7, CtH,) = 0.13 t 0.01, independent of the temperature. The radicals were produced by the photolysis of n-C3F&OC2Hs. The previous determinations of this ratio are discussed and are found to be largely incorrect. The values for A(CF3, CzH5) and A(CzF5, C2H5) are also re-evaluated, and the recommended values are 0.10 2 0.02 and 0.12 t 0.02, respectively. Systems involving perfluoroalkyl and ethyl radicals are complicated due to rapid perfluororadical addition to the ethylene formed in the disproportionation process. The extent of this reaction, and its consequences, are discussed and evaluated. The role of the propionyl (C2H5CO) radical in the room temperature photolysis is also assessed. However, it is found that the A values determined by the intercept method used in this work are not affected by the secondary reactions that occur. It is concluded that high cross-combination ratios are general to perfluoroalkyl-alkyl radical interactions. For C3F7 and CzHs radicals the ratio is 2.7-2.8. Above 100°C ratios exceed 3 due to secondary reactions.

ChemInform Abstract (generated by photolysis of n-C3F7-CO-C2H5).