Large Proton-Affinity Enhancements Triggered by Noncovalent Interactions.

High affinity: The proton affinity (PA) of the OH group of YHx OH compounds is always increased by noncovalent interaction (NCI) with a Lewis base (LB; see figure). This PA enhancement depends on the type of NCI. Weak NCIs can give rise to PA enhancements equal to or even larger than strong NCIs. The binding energies of protonated species play a major role in the case of sigma-hole interactions.