A Spectroscopic Overview of Intramolecular Hydrogen Bonds of NH horizontal ellipsis O,S,N Type

Intramolecular NH horizontal ellipsis O,S,N interactions in non-tautomeric systems are reviewed in a broad range of compounds covering a variety of NH donors and hydrogen bond acceptors. H-1 chemical shifts of NH donors are good tools to study intramolecular hydrogen bonding. However in some cases they have to be corrected for ring current effects. Deuterium isotope effects on C-13 and N-15 chemical shifts and primary isotope effects are usually used to judge the strength of hydrogen bonds. Primary isotope effects are investigated in a new range of magnitudes. Isotope ratios of NH stretching frequencies, nu NH/ND, are revisited. Hydrogen bond energies are reviewed and two-bond deuterium isotope effects on C-13 chemical shifts are investigated as a possible means of estimating hydrogen bond energies.

Automated summary

This review summarizes the intramolecular NH⋯O,S,N interactions in non-tautomeric systems, discussing the use of H-1 chemical shifts, deuterium isotope effects, and primary isotope effects to study hydrogen bond strength. It also explores the two-bond deuterium isotope effects on C-13 chemical shifts as a potential means of estimating hydrogen bond energies.