The electric field gradients (efg) at nitrogen, oxygen, phosphorus, andsulfur have been investigated with ab initio theoretical methods for a series of monofunctional and polyfunctional bases and acids and their ionized forms. Absolute efg values or neutral species are compared with theoretical results from the literature and used to give estimates of NMR line widths in solution. Efg changes occurring upon the acid-base process, expressed as effective nuclear quadrupolar coupling constants, are used to predict changes in the NMR relaxation rates of the pertinent quadrupolar nuclei (N-14, O-17, S-33) upon ionization. This information, joined to relative proton affinities, allows one to predict the preferred ionization site in solution of a given polyfunctional acid or base and to establish criteria whereby such equilibria can be investigated by heteronuclear NMR.