Issue 23, 2021

A new method for detecting intramolecular H-bonds of aromatic amides based on the de-shielding effect of carbonyl groups on β-protons

Abstract

Aromatic amide foldamers with highly predictable conformations possess potential for application in the fields of stereoselective recognition, charge transport and catalysis, whose conformations are commonly limited by the intramolecular hydrogen bonding between amide groups and hydrogen-bonding receptors. Herein, on the basis of the de-shielding effect of carbonyl groups on β-protons, we develop a new method for detecting intramolecular hydrogen bonds of aromatic amide compounds. The solvent-related changes in the βH chemical shifts (Δ(δβH)) and NH chemical shifts (Δ(δNH)) of three kinds of amide compounds, which are frequently used as building blocks of aromatic amide foldamers, were recorded in chloroform, nitromethane, acetonitrile and DMSO. The Δ(δβH) method is found to be highly suitable for studying methoxy-benzamides and fluoro-benzamides in chloroform and DMSO. It is worth noting that a reference compound is not required for applying the Δ(δβH) method, which is an advantage over the Δ(δNH) method. In addition, we extend the Δ(δNH) method from methoxy-benzamides to pyridine-carboxamides and fluoro-benzamides in chloroform and DMSO, and propose that nitromethane and acetonitrile will be possible alternatives for the Δ(δNH) method if a test compound is not soluble in chloroform.

Graphical abstract: A new method for detecting intramolecular H-bonds of aromatic amides based on the de-shielding effect of carbonyl groups on β-protons

Supplementary files

Article information

Article type
Paper
Submitted
11 Mar 2021
Accepted
18 May 2021
First published
21 May 2021

Phys. Chem. Chem. Phys., 2021,23, 13284-13291

A new method for detecting intramolecular H-bonds of aromatic amides based on the de-shielding effect of carbonyl groups on β-protons

J. Min, C. Wang and L. Wang, Phys. Chem. Chem. Phys., 2021, 23, 13284 DOI: 10.1039/D1CP01089A

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