Absolute rate constants for some reactions of perfluoro-n-alkyl radicals in solution

Article abstract of DOI:10.1021/ja00080a012

Absolute rate constants have been measured at 298 ± 2 K for some reactions of C₂F₅·, n-C₃F₇·, n-C₇F₁₅·, and n-C₈F₁₇· by time- resolved (laser flash photolysis) and competition kinetics. The last three of these radicals exhibit essentially equal reactivities, but C₂F₅· is somewhat more reactive. The strongly electrophilic nature of these radicals is illustrated by an outstanding Hammett correlation for the addition of n- C₈F₁₇· to four para-substituted styrenes, log(k(add)/(X)/k(add)/(H)) = - 0.53σ, (r) = 0.99 (X = p-CH₃O to p-CF₃), and, far more significantly, by a respectable correlation, (r) = 0.97, of log k(add) with the ionization potentials (IP) of 13 terminal olefins, the values of k(add) for n-C₃F₇· ranging from 1.6 x 10⁶ to 2.2 x 10⁶ M^-1 s^-1 for CH₂=CHCN (IP = 10.91 eV) to 7.9 x 10⁷ to 8.9 x 10⁷ M^-1 s^-1 for α-methylstyrene (IP = 8.19 eV). The n-C₈F₁₇· radical is 100 times as reactive in hydrogen atom abstraction from tri-n-butyltin hydride as an n-alkyl radical, with k(abs)/(H) (n-C₇F₁₅·) = 2.0 x 10⁸ M^-1 s^-1.