Disproportionation reactions between alkyl and fluoroalkyl radicals. V. Perfluoro-n-propyl and ethyl radicals revisited

✍ Scribed by G. O. Pritchard; S. H. Abbas; J. M. Kennedy; S. J. Paquette; D. B. Hudson; M. A. Meleason; D. D. Shoemaker

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 1019 KB
• Volume: 22
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550221005

✦ Synopsis

Abstract

A redetermination of the disproportionation/combination ratio for n–C~3~F~7~ and C~2~H~5~ radicals gives a value of Δ(n–C~3~F~7~, C~2~H~5~) = 0.13 ± 0.01, independent of the temperature. The radicals were produced by the photolysis of n–C~3~F~7~COC~2~H~5~. The previous determinations of this ratio are discussed and are found to be largely incorrect. The values for Δ(CF~3~, C~2~H~5~) and Δ(C~2~F~5~, C~2~H~5~) are also re‐evaluated, and the recommended values are 0.10 ± 0.02 and 0.12 ± 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 (C~2~H~5~CO) radical in the room temperature photolysis is also assessed. However, it is found that the Δ 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 C~3~F~7~ and C~2~H~5~ radicals the ratio is 2.7–2.8. Above 100°C ratios exceed 3 due to secondary reactions.