59922-54-2Relevant articles and documents
Laser Flash Photolysis of tert-Butyl Aroylperbenzoates: Kinetics of the Singlet and Triplet States and the Aroylphenyl Radicals
Shah, Bipin K.,Neckers, Douglas C.
, p. 1830 - 1835 (2004)
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 for the 550 nm absorption are discussed.
Photoinduced radical cleavage of acylphenyl halides: Different mechanisms for C-I and C-Br bonds
Wagner, Peter J.,Sedon, James,Waite, Carol,Gudmundsdottir, Anna
, p. 10284 - 10285 (2007/10/02)
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Intramolecular Electron Transfer and Dehalogenation of Anion Radicals. 4. Haloacetophenones and Related Compounds
Behar, D.,Neta, P.
, p. 2280 - 2283 (2007/10/02)
Halogen-substituted acetophenones and several other carbonyls and carboxyl derivatives were reduced with eaq- in irradiated aqueous solutions to produce the anion radicals.In certain cases, reduction by (CH3)2C.O- was also used.The anion radicals undergo itramolecular electron transfer and dehalogenation to yield inorganic halide ions.The rates of these reactions varied over a wide range (1E1-1E7 s-1) and were strongly dependent on the nature of the halogen and the other substituent and their relative positions in the molecule.The results obtained here are discussed along with previous measurements on cyano and nitro derivatives.The rate of dehalogenation is found to be dependent on the electron affinity of the other substituent on the ring.Hammett's substituent constants do not correlate with the observed rates.However, spin density distribution in the anion radicals, as derived from ESR parameters, yields a good qualitative correlation.Increased spin density on the ring carbon bearing the halogen is accompanied by an increase in the rate of C-X bond scission.The spin density represents in this case the negative charge density, since protonation of the anion radicals results in minor changes in spin densities but causes a dramatic decrease of the rate of dehalogenation.
