Proton Magnetic Resonance Spectrum of Ammonia and the Interactions Involved in Hydrogen Bond Association

Abstract

High-resolution proton magnetic resonance spectra are presented for the liquid and vapor states of ammonia. The vapor spectrum displays the expected spin-spin interaction multiplet structure. This is likewise found in the liquid state, provided the ammonia is rigorously anhydrous. A trace of water results in the appearance of a single resonance—an effect attributed to chemical exchange of protons. A marked shift of resonance between the liquid and vapor states is found, interpreted as decreased shielding in the liquid state. This effect, not observed for the non-polar substance propane, is discussed in connection with so-called ``hydrogen bonding.''