NMR chemical shielding and spin–spin coupling constants across hydrogen bonds in uracil–α-hydroxy-N-nitrosamine complexes

Relationships between NMR shifts and interaction energies in biphenyls, alkanes, aza‐alkanes, and oxa‐alkanes with X─H…H─Y and X─H…Z (X, Y = C or N; Z = N or O) hydrogen bonding

“…Correlations between hydrogen‐bond strength and spectroscopic parameters go back to Badger and Bauer's work of 1937 on the vibrational spectra of hydrogen‐bonded complexes between alcohols and various solvents . NMR spectral shift enhancement is recognised as a criterion of hydrogen bonding, and many correlations between shifts and different measures of the hydrogen‐bond strength, not only in complexes but also related to intramolecular interactions, have been proposed. Such correlations have been used to infer hydrogen‐bond strengths or distances from spectroscopic data.…”

“…The question arises as to what measure of the bond strength is appropriate for these correlations. Hydrogen‐bond energies, enthalpies, binding energies, and heats of formation, determined by various approaches, have been frequently used, as well as correlations with bond length, it being tacitly or explicitly accepted that energy and bond length are correlated. In the context of QTAIM analysis, when there is a BCP associated with the hydrogen bond, other properties, such as the electron density, ρ, its Laplacian, ∇ 2 ρ, and the potential‐energy density, V, have been exploited .…”