Intramolecular HB Interactions Evidenced in Dibenzoyl Oxalamide Derivatives: NMR, QTAIM, and NCI Studies

Abstract

Extensive NMR spectroscopic studies revealed information on the occurrence of bifurcated intramolecular hydrogen bond in the dibenzoyl oxalamide derivatives. One-dimensional NMR experiments, viz., solvent dilution, temperature perturbation, and two-dimensional experimental techniques, such as N-H HSQC and F-H HOESY, have been exploited to derive unambiguous confirmation of the participation of organic fluorine in the hydrogen-bonding interaction. The experimental NMR findings have been ratified by density functional theory based calculations, viz., NCI (noncovalent interaction) and QTAIM (quantum theory of atoms in molecules).

Intramolecular hydrogen bond directed stable conformations of benzoyl phenyl oxalamides: unambiguous evidence from extensive NMR studies and DFT-based computations

“…With large experimental observations reported by various groups, both in the solution state and solid state, where organic uorine participates in HBs, [20][21][22] this statement may not be relevant in the present day. The existence of N-H/F-C HBs in benzanilides and foldamers has been explored using NMR and X-ray crystallographic studies.…”

Competing HB acceptors: an extensive NMR investigations corroborated by single crystal XRD and DFT calculations

“…However, in many earlier reports, this coupling completely vanished 45,46,48,49 in DMSO except in molecules where the structural restraint resists the complete breaking of HB by DMSO. 26,44 The retention of the 1h J FH for molecule 2 in the DMSO-d 6 is due to the favorable cis geometry (Fig.…”

“…9d), whose value is similar to those observed for other reported molecules. 45,46,[48][49][50][51][52] All these in-depth NMR studies leads to the conclusion that the N-H/X interactions are inuenced by strong pC]O/H HB, which is also reected in the shielding of NH 1 proton and reduced value of 1h J FH in the molecule 2. These narrations suggest that the competitive equilibrium between N-H/X and pC]O/H-N type HBs debilitate with each other and is the possible reason for the shielding of NH 1 proton in the molecules 2 and 3 compared to 1.…”

Intramolecular Hydrogen Bonding Appetency for Conformational Penchants in Oxalohydrazide Fluoro Derivatives: NMR, MD, QTAIM, and NCI Studies

“…The more negative value of the Gibbs free energy indicates the stability of the corresponding conformation. 42 Populations of Conformers. Population analysis has been performed using the Boltzmann distribution, and the values of the percentages (%) of population of the most stable conformation and the second most stable conformation have been calculated.…”