COMPARATIVE ESTIMATION OF THE ENERGIES OF INTRAMOLECULAR С-Hв‹ЇO, N-Hв‹ЇO AND О-Hв‹ЇO HYDROGEN BONDS ACCORDING TO THE QTAIM ANALYSIS AND NMR SPECTROSCOPY DATA
A.V. Vashchenko, A.V. Afonin
Favorsky Institute of Organic Chemistry, Siberian Branch, Russian academy of Sciences, Irkutsk, Russia
Keywords: внутримолекулярная водородная связь, МР2, QTAIM, RDG, intramolecular hydrogen bond, МР2, QTAIM, RDG
Abstract
The energies of intramolecular С-H⋯O, N-H⋯O and О-H⋯O hydrogen bonds in model compounds are empirically estimated based on the values of the hydrogen bond induced weak-field shift of the bridging hydrogen atom signal in the
1Н NMR spectrum. It is supported by a theoretical estimation of these energies based on the electron density value at the hydrogen bond critical point calculated within the QTAIM method. Good agreement between the empirical and theoretical estimates is found, which gives evidence of their reliability. It is shown that from the standpoint of their strength the intramolecular N-H⋯O and О-H⋯O hydrogen bonds can be classified as moderate whereas the intramolecular С-H⋯O hydrogen bonds must be classified as very weak interactions similar in their energy significance to van der Waals interactions.
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