Intra‐ versus intermolecular hydrogen bonding equilibrium in 2‐hydroxy‐N,N‐diethylbenzamide

Abstract

Complex studies of the intramolecular versus intermolecular hydrogen bond equilibrium and internal rotation of the N,N‐diethylamine group in 2‐hydroxy‐N,N‐diethylbenzamide were conducted. The intramolecular versus intermolecular process in 2‐hydroxy‐N,N‐diethylbenzamide was studied by UV–Vis, NMR, IR and Vapour Pressure Osmometric (VPO) methods as a function of temperature and concentration in non‐polar, basic and protic solvents. The unequal positions of the ethyl groups were analysed and the energy barrier to the re‐orientation was defined by the NMR method. This paper presents a study into a complicated nature of competitive interaction 2‐hydroxy‐N,N‐diethylbenzamide with the environment by means of the aforesaid methods. Copyright © 2008 John Wiley & Sons, Ltd.

Difference between 1H NMR signals of primary amide protons as a simple spectral index of the amide intramolecular hydrogen bond strength

“…One of the ways to overcome this problem is to reduce the sample temperatures to slow down the molecular motions, for example by using Freon as a solvent that freeze below 100 K, although usually the solubility of organic molecules in such solvents is low . On the other hand, NMR at room and evaluated temperatures can be successfully applied to study intramolecular or sterically protected H‐bonds …”

“…[3][4][5] On the other hand, NMR at room and evaluated temperatures can be successfully applied to study intramolecular or sterically protected H-bonds. [1,[6][7][8] Hydrogen bonds formed by amides play an important role in biological systems. For example, such H-bonds hold together the secondary structure of proteins and the structure of deoxyribonucleic acid.…”

Intramolecular Hydrogen Bonds in Selected Aromatic Compounds: Recent Developments

“…Therefore, a detailed description of the conformation of systems with the amide moiety is very important. In the papers [66][67][68][69], it was shown that salicylamides can form two types of hydrogen bonds-intramolecular in 5-chloro-2-hydroxy-benzamide and intermolecular in 2-hydroxy-N,N-diethylbenzamide in the solid state ( Figure 14). Studies of the IR, NMR (Nuclear Magnetic Resonance), and UV-Vis spectra, recorded as a function of temperature in non-polar, proton-accepting, and proton-donating solvents [68,69], prove the existence of an equilibrium between intramolecular and intermolecular hydrogen bonds.…”

“…In the papers [66][67][68][69], it was shown that salicylamides can form two types of hydrogen bonds-intramolecular in 5-chloro-2-hydroxy-benzamide and intermolecular in 2-hydroxy-N,N-diethylbenzamide in the solid state ( Figure 14). Studies of the IR, NMR (Nuclear Magnetic Resonance), and UV-Vis spectra, recorded as a function of temperature in non-polar, proton-accepting, and proton-donating solvents [68,69], prove the existence of an equilibrium between intramolecular and intermolecular hydrogen bonds. It is noteworthy that the ease of breaking the strong intramolecular hydrogen bond (e.g., for 4-chloro-2-hydroxybenzamide d(O … O) = 2.526 Å) in 2-hydroxy-N,N-diethylbenzamide is the result of a strong steric effect of ethyl groups and weakened π-electronic coupling between the phenyl and amide fragments [67].…”

“…[68], the 1 H and 13 C NMR spectra of 2-hydroxy-N,N-diethylbenzamide, measured as a function of temperature and solvent polarity, showed the existence of a dynamic effect resulting from the orientation of ethyl groups. On the basis of the temperature-dependent 1 H and 13 C NMR spectra ( Figure 15) and DFT calculations, it was found that the intramolecular hydrogen bond can be observed in aprotic solvents for β-hydroxy naphthalene amides, whereas, in protic solvents (based Studies of the IR, NMR (Nuclear Magnetic Resonance), and UV-Vis spectra, recorded as a function of temperature in non-polar, proton-accepting, and proton-donating solvents [68,69], prove the existence of an equilibrium between intramolecular and intermolecular hydrogen bonds. It is noteworthy that the ease of breaking the strong intramolecular hydrogen bond (e.g., for 4-chloro-2-hydroxybenzamide d(O .…”