Hydrogen-Bond Weakening through π Systems: Resonance-Impaired Hydrogen Bonds (RIHB).

Redefining interactions: The concept of the resonance-impaired hydrogen bond (RIHB) as an interaction in which a conjugated π system strongly impairs the formation of a hydrogen bond (HB) is introduced. A typical HB involving charged species can have a formation energy of tens of kcal mol , whereas the corresponding value for the examined RIHB is only 2.6 kcal mol .