The Effect of Methyl Substitution on Ring Proton Chemical Shifts in Thiophene, Furan and Pyrrole

1961 ◽  
Vol 83 (24) ◽  
pp. 5020-5023 ◽  
Author(s):  
G. S. Reddy ◽  
J. H. Goldstein
Keyword(s):  
Chemical Shifts ◽  
Ring Proton ◽  
Methyl Substitution ◽  
Proton Chemical Shifts

scholarly journals Methyl Substitution Effects on the Proton Chemical Shifts in Benzene

1966 ◽  
Vol 21 (5) ◽  
pp. 609-615 ◽  
Author(s):  
G. S. Reddy
Keyword(s):  
Dipole Moment ◽  
Inverse Relationship ◽  
Chemical Shifts ◽  
Substitution Effects ◽  
Electron Densities ◽  
Methyl Proton ◽  
Methyl Substitution ◽  
Calculated Dipole Moment ◽  
Proton Chemical Shifts ◽  
Good Agreement

Methyl substitution effects on aromatic and methyl proton chemical shifts in several mono-, di-, and trimethyl benzenes are studied. A new method for obtaining the changes in the ring proton chemical shifts from those of methyl proton shifts at the corresponding positions is used. The extra π-electron densities in toluene are calculated using the already known relation between the π-electron densities and the proton shifts in aromatic systems. An inverse relationship is obtained between the ionization potentials and the total methyl effects on the chemical shifts in this series of compounds as one would expect. Dipole moment of toluene is calculated, and a reasonably good agreement is found between the experimentally observed and the calculated dipole moment.

RING-PROTON CHEMICAL SHIFTS OF SOME SUBSTITUTED ANILINES IN CARBON TETRACHLORIDE AND TRIFLUOROACETIC ACID

1963 ◽  
Vol 41 (9) ◽  
pp. 2339-2345 ◽  
Author(s):  
W. F. Reynolds ◽  
T. Schaefer
Keyword(s):  
Carbon Tetrachloride ◽  
Steric Hindrance ◽  
Trifluoroacetic Acid ◽  
Electronic Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Amino Group ◽  
Substituted Anilines ◽  
Ring Proton ◽  
Proton Chemical Shifts

The chemical shifts of the ring-proton spectra of a series of substituted anilines are reported relative to internal benzene in the solvents carbon tetrachloride and trifluoroacetic acid. The substituent parameters in cyclohexane derived by Martin can be used together with our parameters for the para-fluoro and -ammonio (NH3+) groups to demonstrate additivity of the substituent effects in both carbon tetrachloride and trifluoroacetic acid. The somewhat puzzling ring-proton shifts in the latter solvent are attributed to counterion effects arising from a juxtaposition of the two centers of charge. Steric hindrance to π-overlap of the amino group with the ring is demonstrated in certain cases and a parallel behavior is found between the ring-proton shifts and the electronic spectra of these molecules.

NMR-spektroskopische Untersuchungen über zwischenmolekulare Wechselwirkungen bei Benzolderivaten und Pyrrol / NMR-Spectroscopic Investigation of the Intermolecular Reactions of Benzene Derivatives and Pyrrole

1969 ◽  
Vol 24 (11) ◽  
pp. 1365-1370 ◽  
Author(s):  
H.-H. Perkampus ◽  
U. Krüger ◽  
W. Krüger
Keyword(s):  
Dipole Moment ◽  
Temperature Dependence ◽  
Aromatic Compounds ◽  
Spectroscopic Investigation ◽  
Chemical Shifts ◽  
Benzene Derivatives ◽  
Intermolecular Reactions ◽  
Proton Chemical Shifts

The proton chemical shifts of aromatic compounds are strongly concentration dependent. Moreever, for molecules with a dipole moment a temperature dependence of the proton chemical shifts is observed. For hemellitone, p-methylanisole, o-chlortoluene, p-chlortoluene, pyrrole and N-methyl-pyrrole the enthalpies of a dipole-dipole association between -0,7 and -1,8 Kcal could be estimated by NMR measurements combined with the temperature dependence in the whole range of the molefraction (0 → 1).

scholarly journals Real-time prediction of 1H and 13C chemical shifts with DFT accuracy using a 3D graph neural network

2021 ◽  
Author(s):  
Yanfei Guan ◽  
S. V. Shree Sowndarya ◽  
Liliana C. Gallegos ◽  
Peter C. St. John ◽  
Robert S. Paton
Keyword(s):  
Neural Network ◽  
Real Time ◽  
Quantum Chemical ◽  
Organic Molecules ◽  
Chemical Shifts ◽  
13C Chemical Shifts ◽  
Time Prediction ◽  
Nmr Data ◽  
Proton Chemical Shifts

From quantum chemical and experimental NMR data, a 3D graph neural network, CASCADE, has been developed to predict carbon and proton chemical shifts. Stereoisomers and conformers of organic molecules can be correctly distinguished.

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