Solvent effects on nitrogen NMR shieldings in azines

Sicińska, Wanda; Biernat, S.; Webb, G. A.

doi:10.1016/0022-2364(91)90193-w

Cited by 34 publications

(57 citation statements)

References 15 publications

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“…note that these gas-phase protonation energies correlate well with our estimates of hydrogen bonding effects on the nitroWe have previously reported the results of NMR stud-gen shieldings of the other azines studied (1,2). Conseies on the influence of solvents on the nitrogen shielding quently, we may expect that compound I will experience a of, with one exception, all of the existing monocyclic very weak influence on its nitrogen shielding due to solventparent azine heteroaromatics ( 1,2 ) .…”

Section: Introductionsupporting

confidence: 78%

Hydrogen Bonding and Solvent Polarity Effects on the Nitrogen NMR Shielding of 1,2,4,5-Tetrazine

Biedrzycka

Sicińska

Grabowski

et al. 1997

Journal of Magnetic Resonance

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Section: Introductionsupporting

confidence: 78%

Hydrogen Bonding and Solvent Polarity Effects on the Nitrogen NMR Shielding of 1,2,4,5-Tetrazine

Biedrzycka

Sicińska

Grabowski

et al. 1997

Journal of Magnetic Resonance

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“…The latter shows the widest range of solvent-induced shifts (48 ppm), indicating a very high sensitivity to the polarity of the solvent and, among the other unsubstituted azines, the highest basicity in the gas phase, whereas 1,2,4-triazine has the most basic character among the unsubstituted triazines. 45 However, having considered, for both cases, the experimental references determined in cyclohexane, we can only expect a minor shift induced by the solvent. The major cause of the deviation is related to correlation effects, which are extremely important for double-bonded N atoms.…”

Section: Resultsmentioning

confidence: 98%

^14,15N NMR Shielding Constants from Density Functional Theory

2003

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The prediction of nuclear magnetic resonance (NMR) shielding parameters for the N atom represents a particularly difficult task for most of the Hartree-Fock (HF)-based or density functional theory (DFT)-based methodologies. In fact, for some molecular systems, the effect of the presence of a lone pair and multiple bonds on the N atom makes the use of higher correlated methods absolutely necessary to obtain accurate results. In this article, we present an extensive study covering almost the entire spectrum of nitrogen shielding, from +400 to -50 ppm. The sum-over-states density functional perturbation theory (SOS-DFPT) has been used to calculate the shielding constant of 132 different N atoms. The potential of the various SOS-DFPT local approximations has been assessed through the comparison of N atoms that belong to similar molecular systems to experimental data. This procedure allows us to determine the margin of error to be considered in the SOS-DFPT calculation of the isotropic shieldings for each type of N atom.

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“…The results of the present study indicate that such a probe for solvent polarizability-polarity has been found, and this is the nitrogen shielding of tert-butyl isocyanide (1). CH3…”

Section: Introductionmentioning

confidence: 85%

“…The relevant equation is (1) where X Y Z represents the nitrogen shielding for a solute molecule in a given solvent; X Y Z , is the nitrogen shielding in a reference state which is a cyclohexane solution; n* is the polarizability-polarity term for the solvent; a represents its hydrogen bond donor strength; /3 represents its hydrogen bond acceptor strength; 6 is a correction for polychlorinated solvents (6 = 0.5) and aromatic solvents (6 = 1.0); and s, d, a and b are the…”

Section: Introductionmentioning

confidence: 99%

Solvent‐induced variations in nitrogen NMR shieldings of tert‐butyl isocyanide as a probe for solvent polarizability–polarity

Sicińska

Webb

1992

Magnetic Reson in Chemistry

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The nitrogen NMR shielding of tert-butyl isocyanide (1) is shown to be a sensitive probe of solvent polarizabilitypolarity, since the shielding is demonstrated to be unresponsive to hydrogen bonding effects between 1 and the solvent. The direction of solvent e&ts observed is explained in terms of the solvaton model, used within the INDOlssOS framework. A comparison is made with solvent-induced nitrogen shielding variations of the corresponding isomeric covalent cyanides.

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Solvent effects on nitrogen NMR shieldings in azines

Cited by 34 publications

References 15 publications

Hydrogen Bonding and Solvent Polarity Effects on the Nitrogen NMR Shielding of 1,2,4,5-Tetrazine

Hydrogen Bonding and Solvent Polarity Effects on the Nitrogen NMR Shielding of 1,2,4,5-Tetrazine

^14,15N NMR Shielding Constants from Density Functional Theory

Solvent‐induced variations in nitrogen NMR shieldings of tert‐butyl isocyanide as a probe for solvent polarizability–polarity

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