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.

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).

Correlations of substituent effects on proton and fluorine chemical shifts with inverse ionization potentials

1967 ◽  
Vol 45 (24) ◽  
pp. 3143-3151 ◽  
Author(s):  
T. Schaefer ◽  
F. Hruska ◽  
H. M. Hutton
Keyword(s):  
Electric Fields ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Group Iv ◽  
The Other ◽  
Ionization Potentials ◽  
Time Dependent ◽  
Practical Application ◽  
Methyl Proton ◽  
Proton Chemical Shifts

The fluorine and proton chemical shifts in some geminally disubstituted vinylidene fluorides and ethylenes are discussed. For these compounds, at least, there are difficulties with an interpretation based on intramolecular time-dependent electric fields. On the other hand, the shifts correlate with the inverse ionization potentials of the substituents, indicating a paramagnetic effect arising from the second term in Ramsey's expression. It is suggested that the effect operates via the bonds and not across space. Methyl proton shifts in a series of substituted methyl compounds of group IV, V, and VI elements show similar correlations. A practical application of the correlation to spectral analysis problems is given.

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.

Proton chemical shifts and electron densities

1962 ◽  
Vol 34 ◽  
pp. 18 ◽  
Author(s):  
B. P. Dailey ◽  
Albert Gawer ◽  
W. C. Neikam
Keyword(s):  
Chemical Shifts ◽  
Electron Densities ◽  
Proton Chemical Shifts

Proton chemical shifts and ?-electron densities

1968 ◽  
Vol 9 (4) ◽  
pp. 540-544
Author(s):  
R. M. Aminova ◽  
I. D. Morozova
Keyword(s):  
Chemical Shifts ◽  
Electron Densities ◽  
Proton Chemical Shifts

CNDO/2 Electron Densities and Proton Chemical Shifts

1971 ◽  
Vol 49 (10) ◽  
pp. 1779-1781 ◽  
Author(s):  
John F. Sebastian ◽  
John R. Grunwell
Keyword(s):  
Linear Dependence ◽  
Chemical Shifts ◽  
Electron Densities ◽  
Proton Chemical Shifts

An approximate linear dependence of the proton shifts on the CNDO/21 calculated electron densities on hydrogen for C5H5−, C6H6, C7H7+, C5H5NH+, and C6H5CH2− has been found. The significance and limitations of the correlation are discussed.

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