NMR—the chemical shift—IV

ApSimon, John W.; Demarco, Paul V.; Mathieson, D. W.; Craig, W. G.; Karim, Amr M.; Saunders, L.; Whalley, W. B.

doi:10.1016/0040-4020(70)85014-1

Cited by 93 publications

(19 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The nomenclature used by previous authors has been converted [55] to the one used in this series. There is general agreement, although earlier studies [27,57,58] did not differentiate between aliphatic and aromatic carbonyl groups. Although the actual values differ, we note that the carbonyl anisotropy decreases with conjugation with an aromatic ring for ketones, esters and amides.…”

Section: Carbonyl Anisotropysupporting

confidence: 67%

“…An extensive conformational analysis was carried out on aliphatic and aromatic amides using theoretical calculations and NMR and other literature data. The results from the MMFF94 molecular [27] Ketones 13.5 À12.2 - [57] Ketones 21 À6 - [58] Ketones 24 À12 - [16] Amides 4 À9 - [56] Al ketones 22.7 À14.8 67.8 [26] Ar ketones 6.4 À11.9 38.4 [1] Al mechanics force field and the ab initio/DFT methods were comparable. The present model using these geometries can predict the 1 H chemical shifts of amides to within a reasonable accuracy (ca.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

Abraham

Griffiths

Pérez³

2013

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

The (1)H spectra of 37 amides in CDCl(3) solvent were analysed and the chemical shifts obtained. The molecular geometries and conformational analysis of these amides were considered in detail. The NMR spectral assignments are of interest, e.g. the assignments of the formamide NH(2) protons reverse in going from CDCl(3) to more polar solvents. The substituent chemical shifts of the amide group in both aliphatic and aromatic amides were analysed using an approach based on neural network data for near (≤3 bonds removed) protons and the electric field, magnetic anisotropy, steric and for aromatic systems π effects of the amide group for more distant protons. The electric field is calculated from the partial atomic charges on the N.C═O atoms of the amide group. The magnetic anisotropy of the carbonyl group was reproduced with the asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic amides 10.53 and -23.67 (×10(-6) Å(3)/molecule) and for the aromatic amides 2.12 and -10.43 (×10(-6) Å(3)/molecule). The nitrogen anisotropy was 7.62 (×10(-6) Å(3)/molecule). These values are compared with previous literature values. The (1)H chemical shifts were calculated from the semi-empirical approach and also by gauge-independent atomic orbital calculations with the density functional theory method and B3LYP/6-31G(++) (d,p) basis set. The semi-empirical approach gave good agreement with root mean square error of 0.081 ppm for the data set of 280 entries. The gauge-independent atomic orbital approach was generally acceptable, but significant errors (ca. 1 ppm) were found for the NH and CHO protons and also for some other protons.

show abstract

Section: Carbonyl Anisotropysupporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

Abraham

Griffiths

Pérez³

2013

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

“…The cross peak (3,13), which shows the 4-bond W-coupling between H-3 and H-13, gives the precise assignment ofH-3 (0 2.09). The remained spin system (CII-C8-C9-CIO) was observed as the cross peaks (11, 11 '), (11,8), (11', 8), (8,9), (9,10), (11', 10'), (11', 9'), (8,14) and (11,14). The signal of H-11', which was strongly deshielded by the carbonyl group at C4 (discussed later), was weakly coupled with H-IO'.…”

mentioning

confidence: 99%

“…Although the signal of H-9' was not distinguishable from H-9 by their overlapping, the cross peak (11', 9') suggests the presence of a 4-bond W-coupling between H-11' and H-9'. The remaining cross peaks (8,14) and (11, 14) show a 5-bond coupling between each proton. The 5-bond coupling between H-8 and H-14 was also clarified by a decoupling experiment using conventionallH NMR, but coupling between H-11 and He 14 was not observed.…”

mentioning

confidence: 99%

Two-dimensional NMR Investigation of Solanascone

Kodama

Fujimori

Katö³

1984

Agricultural and Biological Chemistry

View full text Add to dashboard Cite

“…Preceding papers in this series (1)(2)(3)(4)(5) have described the derivations of values for the long range shielding parameters of C-C, C-H, C -C , and C--0 bonds. In this paper we report the results of the extension of the method to the ethylene-ketal 1 and -thioketal2 groups.…”

mentioning

confidence: 99%

Chemical Shift. VI. The Long-range Shielding Effects of Ethylene–Ketal and −Thioketal Groups

ApSimon¹,

Beierbeck²,

Todd³

et al. 1971

Can. J. Chem.

View full text Add to dashboard Cite

The calculation of chemical shift values by the method used in parts I–V (1–5) has been extended to a derivation of the shielding effects of the ethylene–ketal and −thioketal groups. For these studies ketal and thioketal derivatives of monoketoandrostanes were prepared. The chemical shifts of the C-18 and -19 methyl protons in these compounds are reported for the solvents CDCl3, CCl4 and benzene.Representing both groups by point dipoles, values for the anisotropies and for K, a parameter descriptive of the electric field effect, were derived for various, coincidental, locations of the magnetic and electric dipoles along the symmetry axes of the two groups.

show abstract

NMR—the chemical shift—IV

Cited by 93 publications

References 19 publications

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

Two-dimensional NMR Investigation of Solanascone

Chemical Shift. VI. The Long-range Shielding Effects of Ethylene–Ketal and −Thioketal Groups

Contact Info

Product

Resources

About

NMR—the chemical shift—IV

Cited by 93 publications

References 19 publications

1H NMR spectra. Part 30: 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

1H NMR spectra. Part 30: 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

Two-dimensional NMR Investigation of Solanascone

Chemical Shift. VI. The Long-range Shielding Effects of Ethylene–Ketal and −Thioketal Groups

Contact Info

Product

Resources

About

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group

¹H NMR spectra. Part 30: ¹H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group