Intramolecular hydrogen bonding in ortho-substituted N,N-dimethylbenzamides

1980 ◽  
Vol 33 (6) ◽  
pp. 1285 ◽  
Author(s):  
CW Fong
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectroscopy ◽  
Chemical Shift ◽  
Hydrogen Bonds ◽  
Carbonyl Group ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Downfield Shift ◽  
Conformational Isomers ◽  
Intramolecular Hydrogen

Intramolecular hydrogen bonding in o-hydroxy-, o-amino- and o-mercapto- N,N-dimethylbenzamide has been examined with the help of 1H, 13C n.m.r. and infrared spectroscopy, a study of barriers to rotation about the C- N bond, and a study of substituent effects using a multi-substituent parameter equation. The cyclic intramolecular hydrogen-bonded structure for the o-mercapto compound is non-planar, and conformational isomers have been detected. The order of relative energies of the hydrogen bonds formed in o-substituted N,N-dimethylbenzamides is OH > NH2 > SH, as determined from a rotational barrier probe. It has beenverified that intramolecular hydrogen bonding causes a downfield shift of the 13C n.m.r. chemical shift of the carbonyl group in these compounds.

Beziehungen zwischen Rotationsisomerie, Wasserstoffbrücken-Bindung und Substituenteneffekten der organischen Chemie / Relations between Rotational Isomerism, Hydrogen Bonding, and Substituent Effects in Organic Chemistry

1972 ◽  
Vol 27 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Gotthard H. Krause ◽  
Herbert Hoyer
Keyword(s):  
Hydrogen Bonding ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Proton Acceptor ◽  
Single Bond ◽  
Free Enthalpy ◽  
Acceptor Group ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The change of free enthalpy involved in intramolecular hydrogen bonding is smaller if the proton acceptor group can rotate round a single bond, as compared to proton acceptor groups which are fixed in a position optimal for hydrogen bonding. Also, the free enthalpy change is altered when the rotation of the proton acceptor is sterically restricted. This is demonstrated by comparing the absorptions of carbonyl stretching vibrations in the infrared spectra of certain compounds showing rotational isomerism. In the present study derivatives of 5-hydroxy-2,2-dimethyl-6-carbomethoxychromanone- (4), 3-nitrosalicylaldehyde and 3-nitro-2-hydroxy-acetophenones substituted in the position 5 and 6 are examined.

Intramolecular Hydrogen Bonding Motifs in Deprotonated Glycine Peptides by Cryogenic Ion Infrared Spectroscopy

2014 ◽  
Vol 118 (22) ◽  
pp. 3906-3912 ◽  
Author(s):  
Brett M. Marsh ◽  
Erin M. Duffy ◽  
Michael T. Soukup ◽  
Jia Zhou ◽  
Etienne Garand
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectroscopy ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen ◽  
Glycine Peptides

Switching On/Off the Intramolecular Hydrogen Bonding of 2-Methoxyphenol Conformers: An NMR Study

2020 ◽  
Vol 73 (3) ◽  
pp. 222
Author(s):  
Frederick Backler ◽  
Feng Wang
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shift ◽  
1H Nmr ◽  
Density Functional ◽  
Point Group ◽  
Decomposition Analysis ◽  
Intramolecular Hydrogen Bonding ◽  
Group Symmetry ◽  
Energy Decomposition Analysis ◽  
Intramolecular Hydrogen

Intramolecular hydrogen bonding of 2-methoxyphenol (2-MP, guaiacol) is studied using NMR spectroscopy combined with quantum mechanical density functional theory (DFT) calculations. The hydrogen bonding of OH⋯O and HO⋯H is switched on in the conformers of anti–syn (AS, 99.64% dominance) and anti–gauche (AG), respectively, with respect to the anti–anti (AA) conformer (without either such hydrogen bonding interactions). It confirms that the 13C and 1H NMR chemical shift of AS dominates the measured NMR spectra, as the AS conformer reproduces the measurements in CDCl3 solvent (RMSD of 1.86ppm for 13C NMR and of 0.27ppm for 1H NMR). The chemical shift of hydroxyl H(1) at 5.66 pm is identified as the fingerprint of the OH(1)⋯OCH3 hydrogen bonding in AS, as it exhibits a significant deshielding from H(1) of AA (4.24ppm) and H(1) of AG (4.38ppm) without such OH(1)⋯OCH3 hydrogen bonding. The AG conformer (C1 point group symmetry) possesses a less strong hydrogen bonding of HO⋯HCH2O, with the methoxyl group out of the aromatic phenol plane. The substituent effect of AG due to the resonance interaction of methoxyl being out of plane in a concentrated solution shifts the ortho- and para-aromatic carbons, C(3)/C(5), of the AG to ~125.05/125.44ppm from the corresponding carbons in AS at 108.81/121.60ppm. The hydrogen bonding exhibits inwards reduction of IR frequency regions of AS and AG from AA. Finally, energy decomposition analysis (EDA) indicates that there is a steric energy of 45.01kcal mol−1 between the AS and AG when different intramolecular hydrogen bonding is switched on.

EFFECT OF INTRAMOLECULAR HYDROGEN BONDING ON IONIZATION CONSTANTS OF SUBSTITUTED SALICYLIC ACIDS

1966 ◽  
Vol 44 (11) ◽  
pp. 1261-1269 ◽  
Author(s):  
G. E. Dunn ◽  
Fei-lin Kung
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Spectrophotometric Method ◽  
Chelate Ring ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Ionization Constants ◽  
Intramolecular Hydrogen ◽  
Hammett Relationship ◽  
Salicylic Acids

Ionization constants at 25 °C have been determined by a spectrophotometric method for 17 substituted salicylic acids. These have been fitted to the simple Hammett relationship and to the extended one proposed by Jaffe, which takes into account the transmission of substituent effects by the o-hydroxy group. The results with Jaffe's equation show that substituent effects on acidity are transmitted only slightly, if at all, through the intramolecular hydrogen bond of a chelate ring. Possible interpretations of the results are discussed.

Sign in / Sign up

Export Citation Format

Share Document