Does Ammonia Hydrogen Bond?

Abstract

Spectroscopic characterizations of the stereochemistry of complexes of ammonia (NH₃) have strongly confirmed some long-held ideas about the weak interactions of NH₃ while casting doubt on others. As expected, NH₃ is observed to be a nearly universal proton acceptor, accepting hydrogen bonds from even some of the weakest proton donors. Surprisingly, no evidence has been found to support the view that NH₃ acts as a proton donor through hydrogen bonding. A critical evaluation of the work that has been done to gather such evidence, as well as of earlier work involving condensed-phase observations, suggests that NH₃ might well be best described as a powerful hydrogen-bond acceptor with little propensity to donate hydrogen bonds.