Selective deshielding of aromatic protons in some ortho-substituted acetanilides

1968 ◽  
Vol 46 (15) ◽  
pp. 2593-2600 ◽  
Author(s):  
James R. Bartels-Keith ◽  
Ronald F. W. Cieciuch
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Solvent Effects ◽  
Proton Magnetic Resonance ◽  
Aromatic Proton ◽  
Intramolecular Hydrogen Bonding ◽  
Low Field ◽  
Intramolecular Hydrogen

Certain ortho-substituted acetanilides exhibit proton magnetic resonance signals at unusually low field for the amido proton and the aromatic proton adjacent to the acetamido group. This effect, explicable in terms of intramolecular hydrogen-bonding, has been observed for nitro, carbonyl, sulfamoyl, and sulfonyl substituents. Solvent effects are discussed.

Aromatic amides. VII. Steric hindrance to hydrogen bonding in ortho-substituted acetanilides

1972 ◽  
Vol 25 (3) ◽  
pp. 639 ◽  
Author(s):  
BD Andrews ◽  
AJ Poynton ◽  
ID Rae
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Steric Hindrance ◽  
Proton Magnetic Resonance ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen ◽  
Magnetic Resonance Spectra

A series of 2-substituted 3,5-dimethylanilines and their N-acetyl derivatives have been synthesized, and their proton magnetic resonance spectra recorded. Intramolecular hydrogen bonding between the amide N-H and the 2-substituent is disturbed by steric hindrance of the 2-substituent only in the case of the 2-nitro, 2-acetyl, and 2-methoxycarbonyl substituents.

Conformations of some dianhydrohexitols

1969 ◽  
Vol 47 (13) ◽  
pp. 2395-2401 ◽  
Author(s):  
F. J. Hopton ◽  
G. H. S. Thomas
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Intramolecular Hydrogen Bonding ◽  
Coupling Constants ◽  
Ring Conformation ◽  
Intramolecular Hydrogen ◽  
Magnetic Resonance Spectra

Proton magnetic resonance spectra of three known diastereoisomers 1,4:3,6-dianhydro-D-glucitol, 1,4:3,6-dianhydro-D-mannitol, 1,4:3,6-dianhydro-L-iditol, and their diacetyl and dimesyl derivatives have been analyzed. The coupling constants obtained have been utilized to determine the conformation of the five-membered rings. Constancy of the couplings between ring protons throughout the series of compounds indicates the existence of one conformation common to all, and this appears to be a composite of the Cs and C2 forms. It is significant that intramolecular hydrogen bonding, which occurs in two of the three diastereoisomers, has little or no effect on ring conformation.

Intramolecular hydrogen bonding in some ortho-nitrodiphenylamines and related compounds. A proton magnetic resonance study

1972 ◽  
Vol 25 (10) ◽  
pp. 2145 ◽  
Author(s):  
DJ Gale ◽  
JFK Wilshire
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Intramolecular Hydrogen Bonding ◽  
Temperature Dependent ◽  
Polar Solvents ◽  
Chemical Shift Data ◽  
Intramolecular Hydrogen ◽  
Related Compounds

.Proton magnetic resonance spectra of a wide variety of substituted 2-nitro- and 2,4-dinitro-diphenylamines and related compounds reveal that long-range coupling occurs between the NH proton and the 5-proton of the nitrophenyl ring in non-polar or weakly polar solvents. However, in the case of the 2,4-dinitrodiphenyl- amines, this coupling is absent in highly polar solvents, except when the non-nitrated ring carries powerful electron-donating substituents, e.g. methoxyl or dimethylamino, ortho or para (but not meta) to the NH group. An examination of these phenomena leads to the conclusion that such long-range coupling provides evidence that intramolecular hydrogen bonding occurs between the NH and the 2-nitro groups. N-Benzyl-2,4-dinitroaniline also exhibited similar long-range coupling but, in dimethyl sulphoxide solut'ion, this coupling was temperature-dependent. The chemical shift data of the ortho-nitrodiphenylamines suggest that they adopt a non-planar skew conformation in solution. A six-bond H-F coupling was observed between the fluorine atom and the 6-proton of 2'-fluoro-2,4-dinitrodiphenylamine.

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