ChemInform Abstract: STRUKTUR UND EIGENSCHAFTEN VON NITRONEN

Минкин, В. И.; Medyantseva, E. A.; Andreeva, I. M.; Gorshkova, G.

doi:10.1002/chin.197315073

Cited by 2 publications

(3 citation statements)

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“…It appears that neither the dipole moment of the parent nitrone nor the dipole moments of any small alkyl derivatives are known. Experimental values exist only for series of α-phenyl N -methyl nitrones and the α-phenyl N -methyl nitrone itself has a dipole moment of 3.55 D 38b. For the parent nitrone, dipole moments of 4.03 and 3.86 D were reported at the CNDO/2 and INDO levels, and these seem overestimated in light of our results.…”

Section: Resultscontrasting

confidence: 80%

Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Glaser

Chen

1997

Chem. Mater.

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The molecules 4-nitropyridine N-oxide (NPO) and 3-methyl-4-nitropyridine N-oxide (POM) and the models nitromethane and N-methylnitrone were studied with ab initio electronic structure theory at the RHF level and with the inclusion of electron correlation using perturbation and density functional theories. At the highest level, MP2(full)/6-311G**// MP2(full)/6-31G*, the dipole moments µ(NPO) ) 0.97 and µ(POM) ) 0.89 D were obtained. Methyl substitution leads to only a small reduction of ∆µ < 0.1 D and the computed dipole moments are in excellent agreement with recent experimental data. The dipole vector of NPO points away from the nitro group (-pole) toward the NO group (+pole) and the dipole vector in POM is rotated such as to point toward the Me-substituted half. The electric quadrupole moments of NPO and POM indicate quadrupolarity {-+ -} along all axes and the |Q zz | values are particularly large. Natural Population analysis reveals the common electronic motif for NPO and POM consisting in an electron-deficient hydrocarbon midsection embedded between electron-rich functional groups. The dipole direction in the pyridine N-oxides thus does not reflect contributions by the quinoid resonance form (electron density shifts from the NO to the NO 2 group) to the ground-state electronic structure. The directions of the molecular dipole moments of the pyridine N-oxides are the simple result of vector addition of the two inward pointing dipoles that are associated with the functional groups and caused by electronegativity differences. In contrast to X-ray electron density studies, the electronic consequences of H/Me replacement are found to be localized. Approximate "molecular dipole moments" based on point charge models (PCM) are compared to the correct dipole moments. The analysis of the PCM-derived dipole moments shows that a discussion of solid-state effects on the molecular dipole moments of NPO and POM must be postponed until the true dipole moments in the crystal have been more rigorously established.

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Section: Resultscontrasting

confidence: 80%

Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Glaser

Chen

1997

Chem. Mater.

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“…We have undertaken a study of the intramolecular hydrogen bond in some N-(R-salicylidene)aniline N-oxides, where R D H (1), 3,5-di-Cl (2) and 3-OCH 3 (3), and N-(2-hydroxynaphthylidene)aniline N-oxide (4) by measuring the deuterium isotope effect on the 13 C NMR chemical shifts.…”

Section: Introductionmentioning

confidence: 99%

“…In this and some other Mannich base N-oxides in solution, a single-minimum intramolecular hydrogen bond is present. 6,7 In order to verify the existence of a proton transfer equilibrium in the Schiff base N-oxides N-(salicylidene)aniline N-oxide (1), N- (3,5-dichlorosalicylidene)aniline N-oxide (2), N- (3-methoxysalicylidene)aniline N-oxide (3) and N-(2-hydroxynaphthylidene)aniline N-oxide (4) in solution, we have reinvestigated their 1 H and 13 C NMR spectra (Table 2) and undertaken an investigation of the deuterium isotope effect on the 13 C chemical shifts. Measurement of the deuterium isotope effect is known to be a very good tool in studying intramolecular hydrogen bond and proton transfer equilibria.…”

mentioning

confidence: 99%

Deuterium isotope effects on ¹³C NMR chemical shifts of some α‐(2‐hydroxyaryl)‐N‐phenylnitrones (Schiff base N‐oxides)

Dziembowska¹,

Rozwadowski²,

Majewski³

et al. 2001

Magnetic Reson in Chemistry

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The deuterium isotope effect on the 13 C NMR chemical shifts of some a-2-hydroxyaryl-N-phenylnitrones (Schiff base N-oxides) was studied. The existence of an intramolecular hydrogen bond with the proton localized on the phenolic oxygen atom was evidenced. Exceptionally large isotope effects 1C-2(D) and 1C-a(D) suggest that the substitution of the proton of the OH group by deuterium leads to a weakening of the hydrogen bond and some conformational changes in the molecule. This conclusion was drawn on the basis of a comparison of the deuterium isotope effects of Schiff base N-oxides and parent Schiff bases.

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ChemInform Abstract: STRUKTUR UND EIGENSCHAFTEN VON NITRONEN

Abstract: Die Dipolmomente und H‐NMR‐Spektren der Nitrone (I)‐(VIII) werden untersucht und diskutiert.

Cited by 2 publications

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Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Deuterium isotope effects on ¹³C NMR chemical shifts of some α‐(2‐hydroxyaryl)‐N‐phenylnitrones (Schiff base N‐oxides)

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ChemInform Abstract: STRUKTUR UND EIGENSCHAFTEN VON NITRONEN

Abstract: Die Dipolmomente und H‐NMR‐Spektren der Nitrone (I)‐(VIII) werden untersucht und diskutiert.

Cited by 2 publications

References 0 publications

Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Electronic Structure Analysis of the Nonlinear Optical Materials 4-NitropyridineN-Oxide (NPO) and 3-Methyl-4-nitropyridineN-Oxide (POM)

Deuterium isotope effects on 13C NMR chemical shifts of some α‐(2‐hydroxyaryl)‐N‐phenylnitrones (Schiff base N‐oxides)

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Deuterium isotope effects on ¹³C NMR chemical shifts of some α‐(2‐hydroxyaryl)‐N‐phenylnitrones (Schiff base N‐oxides)