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.

Nuclear Magnetic Resonance Chemical Shifts of some Monosubstituted Isothiazoles

1975 ◽  
Vol 53 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Thomas R. Clem ◽  
Edwin D. Becker
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Charge Densities ◽  
Monosubstituted Benzenes ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

Carbon-13 and proton chemical shifts have been measured for several monosubstituted isothiazoles. Substituent effects upon these chemical shifts are compared with those observed for monosubstituted benzenes, pyridines, and thiophenes. In general the observed substituent effects in the isothiazoles and thiophenes closely parallel one another. Correlations between the observed carbon-13 Chemical shifts and CNDO/2 calculated charge densities are examined.

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.

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

Temperature dependence of proton magnetic resonance solvent shifts. 3,5-Dichlorosalicylaldehyde in carbon tetrachloride and benzene

1968 ◽  
Vol 46 (19) ◽  
pp. 3110-3112 ◽  
Author(s):  
G. Kotowycz ◽  
T. Schaefer
Keyword(s):  
Carbon Tetrachloride ◽  
Temperature Dependence ◽  
Proton Magnetic Resonance ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Relative Temperature ◽  
Proton Shift ◽  
Solvent Shifts ◽  
Solvent Molecules ◽  
Proton Chemical Shifts

The ring proton chemical shifts of 3,5-dichlorosalicylaldehyde as a function of temperature in carbon tetrachloride and benzene solutions indicate that if there is association with solvent molecules in benzene solution, then there is also association with carbon tetrachloride solvent molecules. The aldehydic proton shift shows a much smaller (relative) temperature dependence in the carbon tetrachloride solution.

Structure of the Second Coordination Sphere of Transition Metal Complexes. II. Substituted Anilines as Ligands

1971 ◽  
Vol 49 (8) ◽  
pp. 1218-1223 ◽  
Author(s):  
D. R. Eaton ◽  
H. O. Ohorodnyk ◽  
Linda Seville
Keyword(s):  
Coordination Sphere ◽  
Methylene Chloride ◽  
Chemical Shifts ◽  
Cobalt Complex ◽  
Cobalt Atom ◽  
Amino Group ◽  
Substituted Anilines ◽  
Second Coordination Sphere ◽  
Solvent Molecules

The role of substituted anilines as second coordination sphere ligands of cobalt(II) complexes has been investigated. Chemical shifts of the ligand nuclear magnetic resonance (n.m.r.) spectra arising from pseudo-contact interaction with the paramagnetic cobalt complex have been utilized for this purpose. It has been found that in each case the aniline preferentially occupies a position perpendicular to the three fold symmetry axis of the complex and tends to be aligned with the amino group directed towards the cobalt atom. Electron withdrawing substituents para to the amino group enhance the second coordination sphere binding and electron donating substituents diminish it. These results are consistent with the idea that the structure of the second coordination sphere is determined by electrostatic interaction with the negatively charged ligands comprising the first coordination sphere. There is competition between aniline molecules and solvent molecules for a position in the second sphere with the solvent competing with increasing effectiveness in the series carbon tetrachloride, benzene, and methylene chloride.

Substituent effects on geminal proton–proton coupling constants

1970 ◽  
Vol 48 (13) ◽  
pp. 2134-2138 ◽  
Author(s):  
Y. L. Chow ◽  
S. Black ◽  
J. E. Blier ◽  
M. M. Tracey
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Hammett Σ Constants

The geminal coupling constants between the non-equivalent benzylic protons of a series of para- and meta-substituted N-benzyl-2-methylpiperidines were shown to be proportional to the Hammett σ constants of the substituents with ρ −1.38 in carbon tetrachloride, −1.21 in benzene, and nearly 0 in 1 N DCl solutions. The ρ values were compared with those of other series and were discussed in terms of the possible conformations involved. The chemical shifts of the benzylic protons of the piperidine derivatives did not give a good correlation with the Hammett σ constants in these solvents.

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