The application of the Biot-Savart law to the ring current analysis of proton chemical shifts—I

Tetrahedron ◽  
1972 ◽  
Vol 28 (14) ◽  
pp. 3613-3633 ◽  
Author(s):  
R.C. Haddon
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Current Analysis ◽  
Proton Chemical Shifts

Substituent-induced 1H chemical shifts for 4-substituted (2, 2-dichlorocyclopropyl)benzenes: further evidence for intramolecular electric field effects on 1H chemical shifts

1977 ◽  
Vol 55 (3) ◽  
pp. 530-535 ◽  
Author(s):  
Robert H. Kohler ◽  
William F. Reynolds
Keyword(s):  
Electric Field ◽  
Field Effect ◽  
Ring Current ◽  
Chemical Shifts ◽  
Basic Pattern ◽  
Electric Field Effects ◽  
Field Effects ◽  
The Individual ◽  
Induced Changes ◽  
Proton Chemical Shifts

Correlations of cyclopropyl proton chemical shifts for 4-substituted (2,2-dichlorocyclopropyl)-benzenes with σI and σR0 provide evidence that these chemical shifts reflect direct field effects and weak phenyl–cyclopropyl conjugative interactions. Corrections for variable ring current effects due to substituent-induced changes in conformation improve the individual correlations but do not alter the basic pattern of results. Correlation of the β cyclopropyl 1H chemical shift difference with σI with calculated hydrogen electron densities, and with calculated electric field components provides further strong evidence for a field effect on 1H chemical shifts.

Definitive Benchmark Study of Ring Current Effects on Amide Proton Chemical Shifts

2011 ◽  
Vol 7 (7) ◽  
pp. 2078-2084 ◽  
Author(s):  
Anders S. Christensen ◽  
Stephan P. A. Sauer ◽  
Jan H. Jensen
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Amide Proton ◽  
Benchmark Study ◽  
Proton Chemical Shifts

Elektronendichte und chemische Verschiebung der Styryldiazin- und Diazaphenanthrenprotonen / Electrondensity and Proton Chemical Shift of Styryldiazines and Diazaphenanthrenes

1972 ◽  
Vol 27 (2) ◽  
pp. 310-319
Author(s):  
H.-H. Perkampus ◽  
Th. Bluhm ◽  
J. Knop
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Current Effect ◽  
Electron Densities ◽  
Paramagnetic Effect ◽  
Nitrogen Lone Pair ◽  
Chemische Verschiebung ◽  
Lone Pair Electrons ◽  
Proton Chemical Shifts

AbstractProton chemical shifts in styryldiazines and diazaphenanthrenes linearly correlate with SCF-π-electron densities of the attached carbon atom and with the electron densities of the hydrogen atom (calculated by the CNDO/2 method). The observed deviations from linearity are discussed in terms of ring current effect, steric effects and the paramagnetic effect of the nitrogen lone pair electrons. An appreciable weakening of ring current is found for diazaphenanthrenes with two adjacent N-atoms. Under the same condition the paramagnetic effect on ortho-hydrogens is increased.

Aromatic interactions in model peptide β-hairpins: Ring current effects on proton chemical shifts

Biopolymers ◽  
2011 ◽  
Vol 98 (3) ◽  
pp. 185-194 ◽  
Author(s):  
Appavu Rajagopal ◽  
Subrayashastry Aravinda ◽  
Srinivasarao Raghothama ◽  
Narayanaswamy Shamala ◽  
Padmanabhan Balaram
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Model Peptide ◽  
Aromatic Interactions ◽  
Proton Chemical Shifts

A Technique for Determining Proton Chemical Shifts arising from Ring Current Effects: the Conformations of Triply Ortho-substituted Diphenyl Ethers

1971 ◽  
Vol 49 (2) ◽  
pp. 225-232 ◽  
Author(s):  
J. J. Bergman ◽  
W. D. Chandler ◽  
R. Y. Moir
Keyword(s):  
Aromatic Ring ◽  
Ring Current ◽  
Chemical Shifts ◽  
Double Difference ◽  
Diphenyl Ethers ◽  
Proton Chemical Shifts ◽  
Ortho Substituent

A double-difference technique, making it possible to obtain that part of proton chemical shifts that originates in the shielding by the second ring in diphenyl compounds, is discussed. Evidence in support of the theory comes from the chemical shifts of aromatic ring protons in a family of triply ortho-substituted diphenyl ethers. The conformations of these ethers appear to be independent of the ortho-substituent, X (X ≠ H), and the COC angle is shown to be approximately 120°.

Ringstrom bei cyclischen Polyenen mit alternierenden und ausgeglichenen Bindungsabständen

1967 ◽  
Vol 22 (1) ◽  
pp. 103-112 ◽  
Author(s):  
F. Baer ◽  
H. Kuhn ◽  
W. Regel
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Electron Systems ◽  
Dimensional Electron ◽  
Nmr Spectrum ◽  
One Dimensional ◽  
Bond Alternation ◽  
Dimensional Electron Gas ◽  
The One ◽  
Proton Chemical Shifts

The ring current effect in NMR has generally been used to distinguish between equal and alternant bonds in cyclic π-electron systems, assuming a strong ring current in equal-bonds-hydrocarbons and no ring current in alternant-bonds-hydrocarbons. A calculation of the ring current is presented based on the one dimensional electron gas model. The effect of bond alternation is considered by a sine curve potential.Proceeding from a model with equal bonds to a model with alternant bonds the ring current is strongly reduced in rings with more than 10 members; it is reduced by 24% and 51% only in 6 and 10 membered rings, respectively. In non-HücKEL type rings with 4 to 16 carbon atoms the ring current is directed opposite to the classical current and is strongest in cyclobutadiene. The contribution of the π-electrons to the susceptibility of these compounds is therefore paramagnetic and ring current shifts opposite to those in HÜCKEL rings are to be expected. These results are confirmed by the proton chemical shifts in the NMR spectrum of [16]-Annulene.

Conformations of Bridged Diphenyls. IV. Diphenyl Ether Conformations and Proton Chemical Shifts

1973 ◽  
Vol 51 (2) ◽  
pp. 162-170 ◽  
Author(s):  
J. J. Bergman ◽  
E. A. H. Griffith ◽  
B. E. Robertson ◽  
W. D. Chandler
Keyword(s):  
Magnetic Anisotropy ◽  
Ring Current ◽  
Chemical Shifts ◽  
Diphenyl Ether ◽  
Current Model ◽  
Diphenyl Ethers ◽  
Proton Chemical Shifts

The conformationally dependent chemical shifts for the ring protons of some diphenyl ethers can be explained approximately by the ring-current model for benzene magnetic anisotropy. Although the model underestimates the shielding in the region above the plane of the ring it is the best of the models investigated for this purpose.

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