8835reduced effective polarity of the interfacial microenvironmentZ8 is also a significant factor in this case in increasing the association of hydrogen ions with the surface carboxyl groups. These points have been made before in connection with the low conductivity above the cmc of perfluorooctanoic acid.I5The neutralization of the surface charges of the micelles of perfluoro acids and the resultant reduction of electrostatic de-(28). (a) Mukerjee, P.; Banerjee, K.stabilization of micelles are also likely to be responsible for an increased stability of the fluorocarbon acid micelles as compared to their salts. Literature datal4 on the strong acid, dodecylsulfonic acid, show that its cmc is lower by a factor of only about 1.15 than the cmc of the sodium salt over a wide temperature range. I n contrast, the cmc of perfluorooctanoic acid, 0.0096 M at 25 "C, is lower than that of the sodium salt, 0.0306 M (Table 11), by a much larger factor of 3.2.
Acknowledgment.Two sulfonyloxyl radicals, CH,S(=O),O*, 2a, and 3-CF3C6H4S(=O),O', 2b, have been generated by 308-nm laser flash photolysis (LFP) of their parent symmetrical peroxides in CH3CN solution, in which they have lifetimes of 7-20 ps. Both radicals exhibit a broad, structureless absorption similar to that known for SO4'-with A, , , -450 nm. This absorption can be bleached for 2a but not for 2b by firing a second laser at 480 nm, presumably reflecting a photoinduced cleavage of the H3C-S03' bond. Radicals 2a and 2b react with the acetonitrile solvent by abstraction of a hydrogen atom, kH -1.6 X I Os M-' s-', kH/kD -2.0. Bimolecular rate constants for attack of these radicals on cyclohexane (viz., 1.9 X lo8 and 6.5 X IO8 M-l s-' for 2s and 2b, respectively) and chloroform (viz. ca., 3 X lo5 M-I S-I for both) demonstrate that they are more reactive than almost all other oxygen-centered radicals. Product studies demonstrate that both the photodecomposition and the thermal decomposition of the parent peroxides yield the corresponding sulfonyloxyl radicals, a result that contrasts with that we have previously obtained for the decomposition of [Ph,P(=O)O],, which yields radicals on photolysis but few if any radicals on thermolysis. Semiempirical AMI /PM3-UHF calculations on 2a are also reported. Transient, highly reactive, oxygen-centered radicals of the general structure Y,X(O)O*, 1, such as aryl-, ethenyl-, and (ethynylcarbonyl)oxyI radicalsz3 (ArC(O)O', RCH=CHC(O)O', and RC=CC(O)O'), (alkoxycarbony1)oxyl radicals4 (ROC-I , ( I I ) Hayon, E.; Treinin, A,; Wilf, J . J . Am. Chem. Soc. 1972, 94, 45-57.
