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.

A carbon-13 CP/MAS nuclear magnetic resonance study of several 1,4-disubstituted benzenes in the solid state

1989 ◽  
Vol 67 (3) ◽  
pp. 525-534 ◽  
Author(s):  
Glenn H. Penner ◽  
Roderick E. Wasylishen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Nuclear Magnetic Resonance Study ◽  
Solution Studies ◽  
Temperature Solution ◽  
Cp Mas Nmr ◽  
Nuclear Magnetic

The carbon-13 chemical shifts of several 1,4-disubstituted benzenes in the solid state are reported. At least one of the substituents is unsymmetrical and in most cases this leads to different 13C chemical shifts of C-2 and C-6 and in some cases to different shifts for C-3 and C-5. The 13C chemical shifts observed in the solid state are compared with those measured in solution and, where possible, with those obtained in low temperature solution studies where internal rotation of the unsymmetrical substituent is slow on the 13C chemical shift time scale. Agreement between the chemical shifts observed in the solid state and solution is excellent. The potential application of CP/MAS nuclear magnetic resonance in deducing the conformation of benzene derivatives with two unsymmetrical substituents is discussed. Keywords: carbon-13 CP/MAS NMR, 13C NMR chemical shifts, substituent effects.

Configurationally dependent hydroxyl group effects on 13C nuclear magnetic resonance chemical shifts of olefinic carbons in cyclic six-membered allylic alcohols

1988 ◽  
Vol 66 (12) ◽  
pp. 3128-3131 ◽  
Author(s):  
Teodoro S. Kaufman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Hydroxyl Group ◽  
Allylic Alcohols ◽  
Stereochemical Assignment ◽  
13C Nuclear Magnetic Resonance ◽  
Group Effects ◽  
Nuclear Magnetic

The differences in chemical shifts of olefinic carbons, Δδ(sp2), of pseudoequatorial and pseudoaxial six-membered allylic alcohols were correlated with the Δδ(sp2) values of their parent olefins. The results obtained reflect configurationally dependent substituent effects, the magnitude of which could be used for the stereochemical assignment of the hydroxyl group in these compounds.

KETO–ENOL TAUTOMERISM IN β-DICARBONYLS STUDIED BY NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY: II. SOLVENT EFFECTS ON PROTON CHEMICAL SHIFTS AND ON EQUILIBRIUM CONSTANTS

1965 ◽  
Vol 43 (5) ◽  
pp. 1516-1526 ◽  
Author(s):  
Max T. Rogers ◽  
Jane L. Burdett
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Tautomeric Equilibrium ◽  
Resonance Spectroscopy ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

The effect of various solvents on the proton chemical shifts of a number of acyclic β-di-ketones and β-ketoesters has been observed by nuclear magnetic resonance spectroscopy. These shifts are discussed in terms of the dissociation of intramolecular and intermolecular hydrogen bonds on dilution. A complex of benzene with the enol tautomer of the β-dicarbonyl molecule is proposed. The effect of solvents on the position of the tautomeric equilibrium is discussed.

Substituent effects by 19F nuclear magnetic resonance: Polar and π-electron effects

1976 ◽  
Vol 29 (12) ◽  
pp. 2571 ◽  
Author(s):  
W Adcock ◽  
BD Gupta ◽  
T Khor
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Electrostatic Field ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Important Conclusion ◽  
Field Effects ◽  
Electron Distributions ◽  
Electron Effects ◽  
Nuclear Magnetic

A number of model substituted bicyclic aryl fluorides, including three new fluorobenzocycloalkenes, have been synthesized and their fluorine- 19 spectra measured. An analysis of the data leads to the important conclusion that electrostatic-field effects play an important role in determining aryl 19F chemical shifts. Further the relative π-electron distributions of several benzocycloalkenes are indicated.

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