1854-28-0Relevant academic research and scientific papers
Atmospheric chemistry of benzaldehyde: UV absorption spectrum and reaction kinetics and mechanisms of the C6H5C(O)O2 radical
Caralp, Francoise,Foucher, Virginie,Lesclaux, Robert,Wallington, Timothy J.,Hurley, Michael D.
, p. 3509 - 3517 (1999)
Flash photolysis-UV absorption and long pathlength FTIR-smog chamber studies of several reactions involving C6H5C(O) and C6H5C(O)O2 radicals have been performed. It was determined that reaction of Cl atoms with C6H5CHO proceeds via abstraction of the aldehydic hydrogen to give benzoyl radicals. The sole atmospheric fate of benzoyl radicals is addition of O2 to give peroxybenzoyl radicals. Reaction of C6H5C(O) radicals with molecular chlorine proceeds with a rate constant of (5.9 ± 0.4) x 10-11 cm3 molecule-1 s-1 at 296 K and 1-700 Torr total pressure. The UV spectrum of C6H5C(O)O2 radicals (245-300 nm) and the self reaction were investigated simultaneously, yielding σ(max) = (2.0 ± 0.1) x 10-17 cm2 molecule-1 at 245 nm and k16 = (3.1 ± 1.4) x 10113 exp[(1110 ± 160) K/T] cm3 molecule-1 s-1, measured from 298 to 460 K. At 338 K, C6H5C(O)O2 radicals react with NO with a rate constant of (1.6 ± 0.4) x 10-11 cm3 molecule-1 s-1. At 296 K, C6H5C(O)O2 radicals react with NO2 with a rate constant of (1.1 ± 0.3) x 10-11 cm3 molecule-1 s-1 to form C6H5C(O)O2NO2, which undergoes thermal decomposition at a rate of k-4 = (2.1+5.0-1.5) x 1016 exp[-(13 600 ± 400)K/T] s-1 in one atmosphere of air. At 296 K in 100-700 Torr of air k[C6H5C(O)O2 + NO]/k[C6H5C(O)2 + NO2] = 1.44 ± 0.15. Relative rate methods were used to measure k[Cl + C6H5C(O)Cl] = (1.1 ± 0.2) x 10-15 cm3 molecule-1 s- 1 at 296 K. Uncertainty limits are all two standard deviations. Results are discussed with respect to the literature data and the atmospheric chemistry of benzaldehyde.
Low-Temperature Photolysis of Benzoyl Peroxide
Kuzina,Bol’shakov,Kulikov,Mikhailov
, p. 189 - 195 (2020/03/31)
Abstract: The photolysis of dry benzoyl peroxide (BP) at 77 K in the 480–236 nm range of wavelengths and an ethanol solution is studied via EPR. It is determined that the main photochemical process in irradiating BP at λ = 480–365 nm is the direct photodi
Dissociation or cyclization: Options for a triad of radicals released from oxime carbamates
McBurney, Roy T.,Walton, John C.
supporting information, p. 7349 - 7354 (2013/06/27)
A set of oxime carbamates having N-alkyl and N,N-dialkyl substituents were prepared via carbonyldiimidazole intermediates. It was shown by EPR spectroscopy that they underwent clean homolysis of their N-O bonds upon UV photolysis. During photolysis of acetophenone O-allylcarbamoyl oxime, the corresponding oxazolidin-2-onylmethyl radical was detected by EPR spectroscopy, providing the first evidence that N-monosubstituted carbamoyloxyl radicals can hold their structural integrity. N,N-Disubstituted carbamoyloxyl radicals dissociated rapidly at the lowest accessible temperatures. Above room temperature, both types of oxime carbamate acted as selective new precursors for aminyl and iminyl radicals. Rate parameters were measured for 5-exo cyclization of N-benzyl-N-pent-4-enylaminyl radicals; the rate constant was smaller than for C-centered and O-centered analogues. Oxime carbamates derived from the volatile diethylamine afforded aryliminyl radicals that proved convenient for phenanthridine preparations.
An optical spectroscopic study on carbon- and oxygen-centered free radical adducts trapped by a bi-functional nitrone spin trap
Sueishi,Yoshioka,Takemoto,Kotake
, p. 1353 - 1360 (2007/10/03)
A hydroxylated nitrone spin trap, α-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone (BHBN), produces distinctive free radical products upon reaction with carbon- and oxygen-centered free radicals. Free radicals were generated from various compound
Radical formation and initiating activity of peroxide-transition metal acetylacetonate systems in low-temperature polymerization
Anisimov
, p. 1784 - 1788 (2007/10/03)
Dependence of the kinetics of radical formation and the initiating activity of redox systems on the nature of the coordinating metal in the chelate initiators is studied. The kinetic scheme of the process is considered, and the calculated and experimental
KINETIC STUDY OF THE REACTION OF BENZOYL PEROXIDE WITH PHENOLIC COMPOUNDS. A TECHNIQUE FOR THE EVALUATION OF PHENOLIC O-H BOND DISSOCIATION ENERGIES
Rousseau-Richard, Claire,Richard, Claude,Martin, Rene
, p. 2057 - 2066 (2007/10/02)
From kinetic data concerning the reaction of benzoyl peroxide (POB) with several phenolic antioxidants (ArOH): POB + ArOH -> C6H5CO2. + C6H5CO2H + ArO., it is shown that differences in the phenolic O-H bond dissociation energies may be obtained.In the particular case of α-tocopherol (α-TH), a stabilization energy defined with respect to phenol: D(C6H5O-H) - D(α-T-H) = 10 kcal.mol-1 has been estimated in heptanol as solvent.It would correspond for α-TH to an O-H bond dissociation energy around 78 kcal.mol-1.
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. 2. Benzoyloxyl and Ring-Substituted Aroyloxyl Radicals
Chateauneuf, J.,Lusztyk, J.,Ingold, K. U.
, p. 2886 - 2893 (2007/10/02)
The 308-nm laser flash photolysis of dibenzoyl peroxide and some ring-substituted derivatives yields broad, structureless absorptions in the range 500-800 nm.These are assigned to the corresponding aroyloxyl radical, in part by analogy with the previously studied 4-methoxybenzoyloxyl radical.Absolute rate constants for reaction of four aroyloxyls with their parent peroxide and with six organic substrates have been measured at ambient temperatures.In general, the rate constants increase along the series 4-CH3OC6H4CO2. . . . both for hydrogen atom abstractions (e.g., with cyclohexane: 5.3 x 105, 2.1 x 106, 1.4 x 106, and 1.2 x 107 M-1s-1, respectively) and for additions (e.g., with benzene: 2.3 x 106, 2.2 x 107, 7.8 x 107, and 2.2 x 108 M-1s-1, respectively).The rates of decarboxylation of aroyloxyl radicals increase along the series (4-FC6H4CO2. . . ca. 4-ClC6H4CO2. . ..Rate constants, k2, for some of these decarboxylations have been determined over a range of temperatures; e.g., for C6H5CO2., log(k2/s-1) = 12.6-8.6/τ, where,τ = 2.3RT kcal/mol.The structure of aroyloxyl radicals is considered and it is concluded that the long-wavelength absorption (ε720nm ca. 290 M-1cm-1 for 4-CH3OC6H4CO2.) is most probably due to a transition from the 2B2 ground state to the 2A1 potential energy surface.The effects of ring substituents on intermolecular reactivity and decarboxylation rates are rationalized in terms of an aroyloxyl structure in which the aromatic ring and carboxyl group are probably coplanar or nearly so and of the contributing valence-bond canonical structures.Some spin-trapping experiments using C6H6 and C6F6 have also been performed.The production of some phenyl radicals in the direct photolysis of dibenzoyl peroxide is indicated by an enhanced yield, relative to the thermal decomposition, of the geminate cage product, phenyl benzoate.However, it is concluded that the yield of phenyl radicals formed in the photolysis is probably considerably less than has been presumed previously.
