N.M.R. and absorption spectra of nitrotoluidines

1974 ◽  
Vol 27 (4) ◽  
pp. 915 ◽  
Author(s):  
T Yokoyama
Keyword(s):  
Hydrogen Bonding ◽  
Absorption Band ◽  
Nitro Group ◽  
Absorption Spectra ◽  
Long Range ◽  
Chemical Shifts ◽  
Intramolecular Hydrogen Bonding ◽  
Polar Solvents ◽  
Dimethylamino Group ◽  
Intramolecular Hydrogen

N.m.r. chemical shifts of ring protons and absorption spectra of 4-substituted 2-nitroaniline deriva- tives were investigated. It was ascertained that the rotations of dimethylamino and/or 2-nitro groups are influenced by the resonance interaction of the dimethylamino group with 4-substituents and the C1 → C2 absorption band is displaced bathochromically by resonance saturation with 4-substituents. The long-range coupling of NH with H5 in N-methyl-2-nitro-p-toluidine was found to be absent and it is considered that the intramolecular hydrogen bonding of amino hydrogen with the 2-nitro group is ruptured by ROH and polar solvents.

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.

Resonance and solvent effects on absorption spectra of 2-nitroaniline derivatives

1976 ◽  
Vol 29 (7) ◽  
pp. 1469 ◽  
Author(s):  
T Yokoyama
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Spectral Data ◽  
Absorption Spectra ◽  
Long Range ◽  
Solvent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Spectral data for N-methyl-2-nitroaniline correlate well with those for N,N-dimethyl-2-nitroaniline in non-hydrogen-bonding, hydrogen-bond-accepting and amphiprotic alcoholic solvents. This same pattern has been reported for N-methyl-2-nitro-p-toluidine. These results indicate that these N-methyl compounds have no hydrogen bonds with any of the solvents studied and intramolecular hydrogen bonding predominates. In the N.M.R. spectra of such amines, long-range coupling between the H5 (ring) and N-H protons is not necessarily evidence for intramolecular hydrogen bonding.� +M substituents at the 4-position increase the twist of the dimethylamino and 2-nitro groups and enhance the C1 → C2 transition, an effect which follows the order of +M abilities of the 4-substituents.

scholarly journals NMR of Natural Products as Potential Drugs

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3763
Author(s):  
Poul Erik Hansen
Keyword(s):  
Natural Products ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Density Functional Theory Calculations ◽  
Intramolecular Hydrogen Bonding ◽  
Chemical Equilibria ◽  
Nmr Techniques ◽  
Intramolecular Hydrogen

This review outlines methods to investigate the structure of natural products with emphasis on intramolecular hydrogen bonding, tautomerism and ionic structures using NMR techniques. The focus is on 1H chemical shifts, isotope effects on chemical shifts and diffusion ordered spectroscopy. In addition, density functional theory calculations are performed to support NMR results. The review demonstrates how hydrogen bonding may lead to specific structures and how chemical equilibria, as well as tautomeric equilibria and ionic structures, can be detected. All these features are important for biological activity and a prerequisite for correct docking experiments and future use as drugs.

Hydrogen Bonding in organic compounds. 1. o-Nitroanilines

1958 ◽  
Vol 11 (4) ◽  
pp. 513 ◽  
Author(s):  
LK Dyall ◽  
AN Hambly
Keyword(s):  
Hydrogen Bonding ◽  
Nitro Group ◽  
Organic Compounds ◽  
Intramolecular Hydrogen Bonding ◽  
Amino Group ◽  
Infra Red ◽  
Sterically Hindered ◽  
Intramolecular Hydrogen

The infra-red spectra of o-nitroanilines do not indicate any intramolecular hydrogen bonding unless there are nitro groups in both positions 2 and 6 to the amino group. An examination of the literature shows that there is no unambiguous evidence from other sources of such bonding in simple o-nitroanilines. An explanation is given of the variation of the stretching frequencies of the nitro group in sterically hindered compounds and in those with electron-donating ortho- and para-substituents.

A carbon-13 nuclear magnetic resonance study of the basicities of aliphatic alcohols

1987 ◽  
Vol 65 (8) ◽  
pp. 1769-1774 ◽  
Author(s):  
Donald G. Lee ◽  
Kenneth J. Demchuk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Hydrogen Bonding ◽  
Chemical Shifts ◽  
Intramolecular Hydrogen Bonding ◽  
Nuclear Magnetic Resonance Study ◽  
Slope Parameter ◽  
Magnetic Resonance Study ◽  
Linear Free Energy ◽  
Intramolecular Hydrogen

Carbon-13 nmr chemical shifts have been used to determine the basicity constants for nine alcohols. The method involves comparing the chemical shifts for carbon atoms adjacent to the site of protonation with those for carbon atoms in a more remote position. The differences in the chemical shifts (Δ values) at different acidities are then used to calculate basicity constants for the alcohols. The pKBH+ values, determined by use of the "X function" are as follows: ethanol −2.12, 1-propanol −2.12, 3-chloro-1-propanol −2.24, 2-chloroethanol −2.45, 2-bromoethanol −2.41, 2-nitroethanol −2.09, 2-methoxyethanol −1.93, 2-phenoxyethanol −1.87, and 2-propanol −2.06. The typical slope parameter, m*, is 0.17. Two linear free energy correlations are obtained: when the alcohols are considered to be a series of monosubstituted ethanols, the Hammett plot has a slope of 0.65; when they are considered to be a series of mono- and disubstituted methanols, the slope is 1.7. Alcohols bearing oxygen-containing substituents are more basic than predicted by about 0.5 pK units, presumably because their conjugate acids can be stabilized by intramolecular hydrogen bonding.

Intramolecular hydrogen bonding of novelo-hydroxythioacetophenones and related compounds evaluated by deuterium isotope effects on13C chemical shifts

2007 ◽  
Vol 45 (3) ◽  
pp. 245-252 ◽  
Author(s):  
Trung Thanh Nguyen ◽  
Thach Ngoc Le ◽  
Fritz Duus ◽  
Bjarke K. V. Hansen ◽  
Poul Erik Hansen
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Deuterium Isotope Effects ◽  
Intramolecular Hydrogen ◽  
Related Compounds
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