Does the five‐member hydrogen bond ring in quinoline carboxamides exist?

Abstract

The presence of intramolecular NHN hydrogen bond in 4‐R‐quinoline‐2‐(N‐R′‐carboxamides) was investigated by AIM methodology. Values of electron density, elipticity, and total energy density at the bond critical point of H···N in amides were compared with respective values of H···O in their N‐oxides. Copyright © 2008 John Wiley & Sons, Ltd.

N–H⋯O versus O–H⋯O: density functional calculation and first principle molecular dynamics study on a quinoline-2-carboxamide N-oxide

“…The results were obtained on the basis of five functionals (with and without Grimme’s correction). A previous AIM study was performed at the DFT B3LYP/6-311++G(d,p) level of theory [ 53 ] and the data found was in agreement with the current results. The inclusion of dispersion effects during the simulations and later during the electron density partitioning did not introduce any significant changes to the results obtained.…”

“…The properties of the H⋯O BCP, especially the rather high electron density, indicate that this bridge is medium–strong. Thus, the properties of the N–H⋯O intramolecular H-bond were reproduced in agreement with the experimental findings [ 12 ] and previous computations [ 53 ].…”

DFT study of H-bonds in the peptide secondary structures: The backbone–side-chain and polar side-chains interactions

“…), which is typical for the non-linear intramolecular H-bonds, e.g. see [33]. According to Table 1, the C5 H-bond disappears if the H. .…”

Conformational influence of quinoline moieties in the crystal packing of bis(quinolinecarboxamide)alkane derivatives

“…The existence of this intramolecular N-H … N hydrogen bond in quinoline-2-carboxamides has been previously studied. 26 In pyridine-2-carboxamides and analogous heterocyclic amides, the formation of intramolecular hydrogen bond toward the nitrogen atom on the aromatic ring is possible as well. 27 For quinoline-2-carboxamides, recent theoretical studies applying the Quantum Theory of Atoms-in-Molecules (QTAIM) 28 and electron densities derived from the B3LYP/6-311++G** electronic wave function have shown the presence of the intramolecular N-H … N hydrogen bond.…”

“…29 This hydrogen bond has been defined as 'very weak and purely electrostatic' by Dziembowska et al and they pointed out that the conformation stability of the secondary 2-quinolinecarboxamides cannot be determined by the N-H … N interactions; on the contrary, they suggest that the coupling of the amide group to the aromatic ring facilitates the formation of the intramolecular hydrogen bond. 26 In the case of N,N9-bis(2-quinolinecarboxamide)alkanes the intramolecular N-H … N quinoline interaction seems to play an important role in the supramolecular arrangement, disrupting totally or partially the formation of the intermolecular N-H … O hydrogen bond. The existence of intramolecular hydrogen bonds in quinoline-2-N-alkyl-carboxamides has been suggested previously on the basis of IR spectra and solvent effects observed on NMR spectra.…”