33574-06-0Relevant articles and documents
Mechanism for photocleavage of N-(anthroyloxy)-9-fluorenylideneamines and dynamic behavior of anthroyloxyl radicals
Saitoh, Yasuo,Kaneko, Makoto,Segawa, Katsunori,Itoh, Hiroki,Sakuragi, Hirochika
, p. 2013 - 2023 (2007/10/03)
Photocleavage of the N-O bond of N-(9-anthroyloxy)-9-fluorenylideneamine and its 1-and 2-anthroyloxy derivatives takes place efficiently in acetonitrile in the excited singlet state attributed to the fluorenylidene moiety. This made it possible for the first time to directly observe anthroyloxyl radicals by the transient absorption method. The quantum efficiency for photocleavage decreases remarkably in benzene, in which the lowest excited singlet state is attributed to the anthroate moiety. All the three kinds of anthroyloxyl radicals are much less reactive in decarboxylation, addition to olefins, and hydrogen-atom abstraction than benzoyloxyl and 1- and 2-naphthoyloxyl radicals; 9-anthroyloxyl radicals supposedly undergo intramolecular addition-elimination in the ipso-position in equilibrium with α-lactonic spirodihydroanthryl radicals, as indicated by one-color and two-color laser photolyses.
A Time-Resolved EPR Study on Photodecomposition of Dibenzoyl Peroxides in Carbon Tetrachloride
Yamauchi, Seigo,Hirota, Noboru,Takahara, Shigeru,Misawa, Hiroaki,Sawabe, Ken,et al.
, p. 4402 - 4407 (2007/10/02)
We have investigated the photodecomposition of a series of dibenzoyl peroxides in carbon tetrachloride by means of time-resolved EPR spectroscopy.The EPR spectra of the intermediate benzoyloxyl and trichloromethyl radicals were identified and the reaction mechanisms were clarified.It is shown that the decarboxylation takes place mostly from the intermediate benzoyloxyl radicals whose lifetimes are on the order of 1 μs at room temperature.The rate constants for the decarboxylation determined from the transient EPR signals were in good agreement with those obtainedfrom the transient absorption.On the basis of the observed polarization of the EPR signals, it is concluded that the spin states of the intermediate radicals are in thermal equilibrium within 0.5 μs after the laser excitation.In aerated systems additional radicals with larger g values were detected and tentatively assigned as phenylperoxyl radicals.
Spectroscopic and Kinetic Characteristics of Aroyloxyl Radicals. 1. The 4-Methoxybenzoyloxyl Radical
Chateauneuf, J.,Lusztyk, J.,Ingold, K. U.
, p. 2877 - 2885 (2007/10/02)
A detailed analysis of the time-resolved, UV-visible spectrum obtained by 308-nm laser flash photolysis of bis(4-methoxybenzoyl) peroxide proves that the broad, structureless absorption in the 500-800-nm region is due to the 4-methoxybenzoyloxyl radical.This radical also has an absorption at 320 nm.The long-wavelength absorption, for which there is less interference from other light-absorbing transients, has been used to measure absolute rate constants, k, for the reaction of 4-methoxybenzoyloxyl with a wide variety of organic substrates at ambient temperatures, e.g., cyclohexane, benzene, triethylsilane, cyclohexene, and 1,3-cyclohexadiene for which k in CCl4 = (5.3 +/- 3.0) x 105, (2.3 +/- ).2) x 106, (4.8 +/- 0.1) x 106, (6.4 +/- 0.3) x 107, and (4.8 +/- 0.2) x 108 M-1s-1, respectively.Compared with the tert-butoxyl radical the 4-methoxybenzoyloxyl radical is about as reactive in hydrogen atom abstractions but is very much more reactive in additions to multiple bonds.The rate constant for decarboxylation of 4-methoxybenzoyloxyl at 24 deg C is (3.4 +/- 0.1) x 105 s-1 in CCl4 but is reduced to 4 s-1 in CH3CN.The 4-methoxybenzoyloxyl radical can also be photodecarboxylated by using 700-nm light from a second laser or by using high power levels in the primary laser.
