Configuration of arylchloromethaniminoxy radicals. A reassignment

Alberti, Angelo; Barbaro, Gaetano; Battaglia, Arturo; Dondoni, Alessandro; Pedulli, Gian Franco

doi:10.1021/jo01309a032

Cited by 10 publications

(20 citation statements)

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“…As mentioned in the Introduction, the assignment of the parameters to the particular isomers was problematic and questionable. 19 The identification of radicals' structures by means of comparison between experimental and theoretical EPR parameters was proven effective, e.g. in refs.…”

Section: Hyperfine Couplingsmentioning

confidence: 99%

“…80,81 Obviously, the intensity of these spectra will depend on molar fractions of µ and ν. This is the case of, inter alia, the E and Z isomers of iminoxyls [19][20][21][22] , the radical anions of terephthaldehyde 82 or bis-Nmethyl-3,4-fulleropyrrolidine 83 . In the opposite case, if the interconversion between µ and ν is fast, then one spectrum consisting of 2I+1 lines is observed and the hyperfine splitting becomes the weighted average of its extreme values for the µ and ν isomers 80,81 :…”

Section: Hyperfine Couplings Averaged Over Rotamersmentioning

confidence: 99%

“…Moreover, a characteristic surge in A F was observed on rising solvent polarity (from 6.6 G in benzene to 10.6 G in DMSO) , and was explained by increasing contribution of the planar dipolar canonical structures of Z s yn isomer with the solvent polarity enhancement . This ascribing of IHFC to Z syn was questioned 12 years later on the basis of further experiments showing that the halogen splitting is much larger in isomers with the CNO • group inversely oriented to ortho -halogen (for E syn ) than when both groups were facing each other (for Z syn ) …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

Witwicki

Jezierska

2015

J. Phys. Chem. A

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Iminoxy radicals (R1R2C═N—O•) possess an inherent ability to exist as E and Z isomers. Although isotropic hyperfine couplings for the species with R1 = H allow one to distinguish between E and Z, unequivocal assignment of the parameters observed in the EPR spectra of the radicals without the hydrogen atom at the azomethine carbon to the right isomer is not a simple task. The iminoxyl derived from o-fluoroacetophenone oxime (R1 = CH3 and R2 = o-FC6H5) appears to be a case in point. Moreover, for its two isomers the rotation of the o-FC6H5 group brings into existence the syn and anti conformers, depending on the mutual orientation of the F atom and C═N—O• group, making a description of hyperfine couplings to structure even more challenging. To accomplish this, a vast array of theoretical methods (DFT, OO-SCS-MP2, QCISD) was used to calculate the isotropic hyperfine couplings. The comparison between experimental and theoretical values revealed that the E isomer is the dominant radical form, for which a fast interconversion between anti and syn conformers is expected. In addition, the origin of the significant AF increase with solvent polarity was analyzed.

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Section: Hyperfine Couplingsmentioning

confidence: 99%

Section: Hyperfine Couplings Averaged Over Rotamersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

Witwicki

Jezierska

2015

J. Phys. Chem. A

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“…Related iminoxyl radicals all had nitrogen hfs of 30-31 G in tert-butylbenzene (for both syn and anti isomers). 34 Acyloxyaminoxyls are also extremely persistent, and the observed radicals may have been 27, formed by addition of the stannyl radical followed by oxidation with a trace amount of oxygen. Related α-chloroalkoxyaminoxyl radicals have previously been observed in water, 35 benzene 36 and trichlorofluoromethane.…”

Section: Epr Spectroscopic Investigation Of Radical Generation From O...mentioning

confidence: 99%

“…214, benzonitrile; peak no. 308, 3-tert-butylcyclohexanone, 154 (M ϩ ) (8), 98 (40), 97 (28), 83 (18), 69 (31), 57 (100), 55 (44), 41 (92), 29 (34), 27 (26); peak nos. 500 and 535, cyclohexenone cycloadducts.…”

Section: Photochemical Reaction Of O-trimethylacetyl Benzaldoxime 3a ...mentioning

confidence: 99%

Exploitation of aldoxime esters as radical precursors in preparative and EPR spectroscopic roles

McCarroll

Walton

2000

J. Chem. Soc., Perkin Trans. 2

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Photolyses of aldoxime esters, containing a considerable range of alkyl groups, lead to cleavage of their N-O bonds and formation of aryliminyl and alkyl radicals. The process was found to be favoured by 4-methoxyacetophenone as a photosensitiser and by methoxy substituents in the aryl rings. 4-Nitro-and pentafluoro-substitutions of the aryl rings were, on the other hand, deleterious. The intermediate iminyl radicals, together with primary, secondary and tertiary alkyl radicals were characterised by 9 GHz EPR spectroscopy. Cyclopropyl, CF 3 , and CCl 3 radicals were probably also formed, but were too reactive for direct EPR spectroscopic detection. Photosensitised reaction of benzophenone oxime O-nonanoyl ester produced the diphenylmethaniminoxyl, as well as the expected n-octyl and iminyl radicals. This indicated that O-C bond scission accompanied O-N scission for this ketoxime ester.At higher temperatures the C-centred radicals added to the starting oxime esters to produce alkoxyaminyl radicals that were also spectroscopically detected in some cases. No evidence for abstraction of the iminyl hydrogen by tertbutoxyl radicals was obtained. Instead, the t-BuO ؒ radicals added to the C᎐ ᎐ N double bonds of the oxime esters. Similarly, chlorine abstraction from alkylbenzohydroximoyl chlorides by trimethyltin radicals did not take place. Preparative scale experiments with oxime esters containing suitably unsaturated alkyl groups showed that good yields of cyclised products could be obtained in the presence of the photosensitiser. This process constitutes a general method by which carboxylic acids or acid chlorides can be converted into alkyl radicals and hence to cyclised derivatives.

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ChemInform Abstract: CONFIGURATION OF ARYLCHLOROMETHANIMINOXY RADICALS. A REASSIGNMENT

Alberti¹,

Barbaro²,

Battaglia³

et al. 1981

Chemischer Informationsdienst

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Configuration of arylchloromethaniminoxy radicals. A reassignment

Cited by 10 publications

References 0 publications

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

Exploitation of aldoxime esters as radical precursors in preparative and EPR spectroscopic roles

ChemInform Abstract: CONFIGURATION OF ARYLCHLOROMETHANIMINOXY RADICALS. A REASSIGNMENT

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