Absolute rate constants for radical additions to alkenes in solution. The synergistic effect of perfluorination on the reactivities of n-alkyl radicals

Article abstract of DOI:10.1021/jo951782v

Laser flash photolysis has been used to determine the absolute rate constants for addition of several partially fluorinated n-alkyl radicals to three styrenes at 25°C in Freon 113. Fluorination at the γ-position (RCF₂CH₂CH₂?) gives radicals with essentially the same reactivity as non-fluorinated n-alkyls. The RCH ₂CF₂CH₂? and RCH₂CH ₂CHF? radicals are both about three times as reactive as RCF₂CH₂CH₂?, but the RCH ₂CH₂CF2? radical is ca. five to six times rather than ca. three times as reactive as RCH₂CH₂CHF?. Similarly, the perfluorinated radical CF₃CF₂CF ₂? is much more reactive than would be expected on the basis of the reactivities of the RCH₂CF₂CH₂? and RCH₂CH₂CF₂? radicals. Thus, perfluorinated n-alkyl radicals are very considerably more reactive than would be predicted from the individual effects of α, β-, and γ-fluorination.