B. S. and, D. Neckers
Jan 27, 2004
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Influential Citations
19
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Journal
Journal of the American Chemical Society
Abstract
tert-Butyl aroylperbenzoates (1−4) were studied by laser flash photolysis (LFP). LFP (380 nm, pulse width ∼350 fs) of 2 and 3 allowed direct observation of their singlet states, which showed broad absorption (λmax ∼ 625 nm; τ ∼ 20 and ∼7.9 ps, respectively). The triplet state of each (λmax ∼ 530−560 nm) rapidly dissociates by O−O cleavage as indicated by the short triplet lifetimes (e.g., triplet lifetime of 3 ∼0.74 ns). The ∼550 nm absorption obtained from the 355 nm LFP (pulse width ∼7 ns) of 1, 2, and 4 has been assigned to the corresponding aroylphenyl radicals. Two representative radicals (4-benzoylphenyl 5 and 3-(4‘-methylbenzoyl)phenyl 6) investigated in detail showed solvent-dependent lifetimes. Absolute bimolecular rate constants of reactions of these radicals with various quenchers including double-bond-containing monomers have been observed to range from 7.56 × 107 to 1.68 × 109 M-1 s-1 in CCl4 at room temperature. A possible structure of the aroylphenyl radicals and the transition responsible ...