The Neophyl-like Rearrangement of Alkoxyl Radicals Revisited: Laser Flash and Laser Drop Photolysis Studies of 1,1-Diphenylethoxyl Radicals

Article abstract of DOI:10.1021/j100011a020

The radical 1,1-diphenylethoxyl (III) has been generated by laser photodecomposition of tert-butyl 1,1-diphenylethyl peroxide (II).Radical III shows a visible absorption with λ_max 535 nm and decays by phenyl migration to yield the 1-phenoxy-1-phenylethyl radical (V).The conversion III->V occurs with an activation energy of 5.9 +/- 0.4 kcal/mol and a preexponential factor (log A/s^-1) = 10.77 +/- 0.35, corresponding to a lifetime for III of ca. 400 ns in acetonitrile at room temperature.In the nanosecond time scale, the formation of V occurs concurrently with the decay of III.The results suggest that there is no need to invoke the intermedicay of the neophyl-like bridged intermediate IV.This intermediate is probably involved but if so is short-lived and not detectable with nanosecond laser photolysis tecniques.The conclusion of earlier reports involving the characterization of IV needs to be revised.High-intensity laser excitation of II under laser drop conditions shows that III undergoes C-C photocleavage to yield acetophenone and benzophenone with virtually no selectivity.