Electron resonance studies of fluorine hyperfine interactions

Carrington, Alan; Hudson, Andrew; Longuet‐Higgins, H. C.

doi:10.1080/00268976500100511

Cited by 53 publications

(14 citation statements)

References 20 publications

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“…Of the remaining four coupling constants it appears reasonable to assign the largest coupling of 3.91 G to the para position proton, the couplings of 3.16 and 3.37 G to the two remaining ortho position protons, and the 2.92 G splitting to the 19F nucleus. The assignment of coupling constants in this manner agrees with the ordering of splittings of Carrington et al (5). Further confidence in the above assignment is given by the work of Kaplan et al (4) on the anion radical of 3,5-difluoro-nitrobenzene.…”

Section: Assignment Of Coupling Constants and Spinsupporting

confidence: 86%

“…The techniques. A~~~~~~ these are the fluoranil anion radicals of o-and m-fluoro-nitrobenzene, semiquinone (I), monofluorinated nitrobenzene for instance, have been rerecorded in aprotic radicals (2)(3)(4)(5), p-fluoro-acetophenone (6), 2,7-di-solvents to exclude strong solvation effects as fluoro-fluorenone (7), and recently some highly be found in aqueous 'ystems (5). The fluorinated nitro and nitroso radicals (8).…”

Section: Introductionmentioning

confidence: 99%

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Electron spin resonance of fluorine-substituted nitro-aromatic anion radicals

Fischer¹,

Zimmermann²

1968

Can. J. Chem.

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Electron spin resonance spectra have been observed for anion radicals derived from 2-fluoro-nitro-benzene, 3-fluoro-nitrobenzene, 2,4-difluoro-nitrobenzene, 2,5-difluoro-nitrobenzene, 4-fluoro-2-nitro-phenol, 2-fluoro-6-nitrophenol, and 3-fluoro-6-nitrophenol. All radicals were generated electrolytically in dimethoxyethane/acetonitrile solution, acetonitrile, or dimethylformamide. The radicals are generally quite stable with the exception of those from 2-fluoro-6-nitrophenol and 3-fluoro-6-nitrophenol, the latter decaying with a half-life of approximately 6 min. All spectra can be interpreted completely, and coupling constants are assigned by comparison to related compounds and consistency arguments

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Section: Assignment Of Coupling Constants and Spinsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Electron spin resonance of fluorine-substituted nitro-aromatic anion radicals

Fischer¹,

Zimmermann²

1968

Can. J. Chem.

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“…They are similar to the HiickelMcLachlan values given by Carrington et al [38]. An advantage of the CNDO/2 method is that it enables a more satisfactory treatment of the rotation of the NO2 group to be made than by a purely ~r-electron calculation.…”

Section: -C6hsfsupporting

confidence: 65%

“…Unfortunately there is no experimental information available on hyperfine splittings at the oxygen atoms. Calculations with the plane of the NO2 group perpendicular to the ring plane confirm the view that the odd electron is more localized on the NO2 group as the latter rotates away from the plane of the ring [38,41,42].…”

Section: -C6hsfsupporting

confidence: 63%

All valency electron molecular orbital calculations

Davies

1967

Molecular Physics

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The approximate self-consistent molecular orbital method CNDO/2 is applied to calculations on all the valency electrons of some fluorobenzenes and fluoronitrobenzenes. The charge distribution, which shows a-electron acceptance and rr-electron donation by the fluorine atoms, is in accordance with general chemical ideas. It leads to satisfactory values for the dipole moments of the fluorobenzenes and slightly less good values for the fluoronitrobenzenes. The spin densities on the carbon, nitrogen and oxygen atoms obtained for the anions of the fluoronitrobenzenes by the unrestricted form of the method give a satisfactory representation of the experimental hyperfine splitting constants. The elements of the bond order matrix are used with the average energy approximation and theoretical values for r -3 integrals to obtain relative shielding constants for the fluorine nuclei. The assumption made by other workers that the a-electron terms are effectively constant for the fluorobenzenes is found to be justified. With the average energy as an empirical parameter good agreement is obtained with the experimental chemical shifts, and evidence for an ortho effect is found. The results suggest that the overall electronic structure obtained for these molecules by the CNDO/2 method is satisfactory; but that some modification of the values for the 7r-electron resonance integrals may be desirable.

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“…Thus, he reassigned the spectra of the photoparamagnetic intermediate to the radical PhN(0)OH and suggested that the excited nitrobenzene abstracted a hydrogen atom from the solvent as the initial step in the photoreduction of aromatic nitrocompounds. This interpretation has gained general acceptance in the past (5)(6)(7)(8). However, Cowley and Sutcliffe (9) have recently reported some good evidence that the photointermediate in the photolysis of nitrobenzene has the structure P~N ( o ) O R , in which R is the solvent radical.…”

Section: Introductionmentioning

confidence: 98%

Some Electron Spin Resonance Observations in the Photoreduction of Nitrobenzenes

Wong¹,

Wan²

1973

Can. J. Chem.

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The photoreduction of some nitrobenzenes in various organic solvents was re-investigated by e.s.r. and the rapid scan e.s.r. method. The present study resolved the contradicting e.s.r. assignments of the radical observed in the photoreduction of nitrobenzene in tetrahydrofuran and confirmed the identification of the radical PhN(0)OR. All other radicals observed in various solvents were identified and their formation can he explained by secondary processes in the photoreduction.

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Electron resonance studies of fluorine hyperfine interactions

Abstract: Radicals derived from five fluoronitrobenzenes have been prepared and their E.S.R. spectra measured. The hyperfine splittings are discussed and evidence is presented for steric hindrance of a nitro group when it has two orthofluorine neighbours.

Cited by 53 publications

References 20 publications

Electron spin resonance of fluorine-substituted nitro-aromatic anion radicals

Electron spin resonance of fluorine-substituted nitro-aromatic anion radicals

All valency electron molecular orbital calculations

Some Electron Spin Resonance Observations in the Photoreduction of Nitrobenzenes

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