ABSOLUTE RATE CONSTANTS FOR RADICAL ADDITIONS TO ALKENES IN SOLUTION - THE SYNERGISTIC EFFECT OF PERFLUORINATION ON THE REACTIVITIES OF N-ALKYL RADICALS

Laser flash photolysis has been used to determine the absolute rate co nstants for addition of several partially fluorinated n-alkyl radicals to three styrenes at 25 degrees C in Freon 113. Fluorination at the t heta-position (RCF(2)CH(2)CH(2) .) gives radicals with essentially the same reactivity as non-fluorinated n-alkyls. The RCH(2)CF(2)CH(2) . a nd RCH(2)CH(2)CHF . radicals are both about three times as reactive as RCF(2)CH(2)CH(2) ., but the RCH(2)CH(2)CF(2) . radical is ca. five to six times rather than ca. three times as reactive as RCH(2)CH(2)CHF . . Similarly, the perfluorinated radical CF3CF2CF2 . is much more react ive than would be expected on the basis of the reactivities of the RCH (2)CF(2)CH(2) . and RCH(2)CH(2)CF(2) . radicals. Thus, perfluorinated n-alkyl radicals are very considerably more reactive than would be pre dicted from the individual effects of alpha-, beta-, and gamma-fluorin ation.