Bridged [18]annulenes. 12b,12c,12d,12e,12f,12g-Hexahydrocoronene and its mono- and dibenzo analogs. Ring-current contribution to chemical shifts as a measure of degree of aromaticity

1978 ◽  
Vol 100 (8) ◽  
pp. 2449-2456 ◽  
Author(s):  
T. Otsubo ◽  
R. Gray ◽  
V. Boekelheide
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Current Contribution ◽  
Degree Of Aromaticity

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.

Carbon-13 Nuclear Magnetic Resonance Studies of Some Methyl Substituted Diphenylmethanes

1974 ◽  
Vol 52 (18) ◽  
pp. 3196-3200 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Giorgio Montaudo ◽  
Paolo Finocchiaro
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Ring Current ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic

Carbon-13 n.m.r. chemical shifts are reported for diphenylmethane and nine methylated derivatives. Results are compared with those for related methylbenzenes. In the case of tri-ortho-substituted materials the predominance of a perpendicular conformation is suggested. Ring current calculations show that in contrast to the 1H chemical shift interpretations, the 13C shielding trends cannot originate primarily from anisotropic effects.

Sign in / Sign up

Export Citation Format

Share Document