Electron spin resonance study of phenyl radicals isolated in an argon matrix at 4.deg.K

Kasai, Paul H.; Hedaya, E.; Whipple, Earl B.

doi:10.1021/ja01044a008

Cited by 96 publications

(52 citation statements)

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“…9 G for meta-and paraprotons, respectively. 13 The observed hyperfine splitting in the designated part of central signal [ Fig. 8(A)] is 5 -6 G, which is indeed close to the above mentioned value due to the meta-proton.…”

Section: Bandsupporting

confidence: 75%

Ionic intermediates produced by gamma irradiation at 4 K: Halogenated naphthalene and benzene derivatives in ethanol

Namiki

1975

The Journal of Chemical Physics

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Optical absorption and ESR measurements have been performed for the irradiated halogenated benzene and naphthalene derivatives in ethanol at 4 K. The anions of both bromo-and chloronaphthalene derivatives were observed under steady state at 4 K, while the former anion at 77 K results in dissociation and the latter anion results in protonation. Both anions of benzene and fluorobenzene were stable at 4 K, whereas not at 77 K, indicating that protonation is inhibited at 4 K. Irradiated iodobenzene and bromobenzene solutions at 4 K showed a doublet band whose energy separation was 0.8--D.9 and 0.41--D.48 eV, which are close to the energy separation between 2 P J!2 and 2 PI 12 of I and Br, respectively. The transition energies of the long wavelength bands of these compounds and of chlorobenzene is linear with the ionization potentials of respective halide ions with a slope of close to unity. Therefore these bands may be assigned to an electron transfer band from halide ion to its counterpart benzene ring. As the electron acceptor, two models were discussed, one of which is the orbital of neutral benzene, and the other is the orbital of the phenyl radical. In solid phase, dissociative electron attachment to halogenated benzene goes through a state of metastable C T complex of a halide ion and its counterpart molecule. The irradiated p -C 6 H.BrI showed also a well resolved doublet band, suggesting that C-I bond rupture is more dominant than C-Br bond rupture. The absorption spectrum of irradiated p -C 6 H.BrCI in ethanol did not resemble either the irradiated chlorobenzene or bromobenzene derivatives, suggesting that both C-Br and C-CI are ruptured at the same time.990

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Section: Bandsupporting

confidence: 75%

Ionic intermediates produced by gamma irradiation at 4 K: Halogenated naphthalene and benzene derivatives in ethanol

Namiki

1975

The Journal of Chemical Physics

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“…According to previous reports, isotropic hypefine splitting (hfs) of phenyl radicals is about 1.7 to 1.8 mT for ortho protons and approx. 0.6 to 0.7 mT for meta protons . There is no such a pattern in the experimental spectra at 77 K because the extent of the signal is twice as low as the sum of hfs equal to 5.0 mT.…”

Section: Resultsmentioning

confidence: 88%

“…16,17 There is no such a pattern in the experimental spectra at 77 K because the extent of the signal is twice as low as the sum of hfs equal to 5.0 mT. Due to the unusual reactivity, the intermediate was observed only at 4 K or after being trapped in the appropriate matrix at 77 K. 17 The successor of phenyl radical, phenyl peroxyl radical (PhOO • ), is formed via oxidation, Scheme 1. The characteristic asymmetric singlet observed at higher temperatures can be assigned to this product.…”

Section: Discussion Of Epr Spectroscopy Resultsmentioning

confidence: 99%

Radical processes initiated by ionizing radiation in PEEK and their macroscopic consequences

Kornacka

Przybytniak

Nowicki

2018

Polymers for Advanced Techs

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Poly (ether ether ketone) was irradiated with gamma rays or electron beam to investigate the radical process. The generated paramagnetic species were observed by electron spin resonance spectroscopy at ambient temperature and in liquid nitrogen. The effect of microwave power on saturation of the particular spectra and thermal annealing effects were determined. The following radicals were identified: radical anion, phenoxyl radical, and phenylperoxy radical. Despite the fact that the intermediates were formed as a result of backbone cleavage causing degradation, the macroscopic features were almost unaffected by irradiation up to dose of 1500 kGy.

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“…Second-order corrections have been made. The relative values are believed accurate to f l in the fifth decimal place Radicals were produced by removal of Br-from the appropriate bromide by reaction with eaq-(reaction 4) or by removal of a carboxyl group from the appropriate carboxylate ion by reaction with so4-(reaction 1). Values observed for this radical in an argon matrix are a.…”

Section: 00246mentioning

confidence: 99%

Electron spin resonance studies of phenyl and pyridyl radicals in aqueous solution

Zemel¹,

Fessenden²

1975

J. Phys. Chem.

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Publication costs assisted by Carnegie-Meilon University and the U. S. Energy Research and Development AdministrationESR spectra of a number of phenyl and 2-pyridyl radicals have been detected in aqueous solution. Two methods of radical production were used, namely, reaction of SO4.-produced by photolysis of &Os2-with aromatic carboxylate ions and reaction of eaq-produced by radiolysis with aromatic bromides. Most radicals had only carboxyl groups as further substituents. The proton hyperfine constants of the phenyl radicals, a, -17, um -6, and up -2 G, are readily assigned on the basis of effects of the various substitutions and agree well with previous determinations for radicals in the solid state. With four phenyl radicals containing two to four carboxyl groups it was also possible to detect all of the possible 13C containing isomers at natural abundance. A hyperfine constant of -135 G for the carbon at the radical site confirms the u nature of phenyl radical. The other ring 13C hyperfine constants are uoc -7.5, urnc -13, and upc -1.5 G.Both 14N and proton hyperfine constants were determined for the 2-pyridyl radicals. Only the 14N value (-27 G) was known previously. The g factors of phenyl and 2-pyridyl radicals are low (near or below the free electron value) reflecting their u nature. The presence of carboxyl groups in a phenyl radical affects the g factor in an additive fashion with increments of 13, -2, and -3 units in the fifth decimal place for ortho, meta, and para substituents, respectively. The observation of phenyl and 2-pyridyl radicals demonstrates in a direct way that these radicals are formed in the two above-mentioned reactions. (One example each of a 4-pyridyl and a pyrazyl radical were also produced and studied.) Phenyl and 2-pyridyl radicals with no ortho carboxyl group were found to be very reactive toward addition to another aromatic molecule and were best detected using low concentrations (5 X lov4 M ) of aromatic bromide. Spectra of the unsubstituted phenyl and 2-pyridyl radicals were obtained in this way from the corresponding bromides. At higher solute concentrations such as used for the decarboxylation reactions these radicals react further to form adducts of the cyclohexadienyl type. Radicals with an ortho carboxyl group (for example, 2-carboxylphenyl radical produced from phthalate) are much less reactive toward addition and could be studied at higher concentrations of the starting compound. Reaction of SO4--with acids in which three (or more) adjacent carboxyl groups are present leads preferentially to loss of a central or interior carboxyl group. To provide data for comparison with earlier indirect studies, a number of adducts of phenyl and pyridyl radicals to CH2=N02-and trimesate were studied and their hyperfine constants determined. In the latter cases it was found that the ortho and meta protons in the phenyl radical which has added (i.e., the side group in the final cyclohexadienyl radical) can produce splittings of -0.05 and -0.3 G, respectively. The radicals detected in exp...

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Electron spin resonance study of phenyl radicals isolated in an argon matrix at 4.deg.K

Cited by 96 publications

References 0 publications

Ionic intermediates produced by gamma irradiation at 4 K: Halogenated naphthalene and benzene derivatives in ethanol

Ionic intermediates produced by gamma irradiation at 4 K: Halogenated naphthalene and benzene derivatives in ethanol

Radical processes initiated by ionizing radiation in PEEK and their macroscopic consequences

Electron spin resonance studies of phenyl and pyridyl radicals in aqueous solution

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