A NOVEL METHOD FOR THE DETERMINATION OF IONIZATION SITES IN POLYFUNCTIONAL ACIDS AND BASES BY NMR RELAXATION RATE MEASUREMENTS

A method which enables one to determine the site of ionization in polyfunctional acids and bases is presented. The method is based on the changes in NMR longitudinal relaxation time (T1) of all the nuclei potentially involved, because addition or removal of a proton from a given nuclear site will affect its T1 in a predictable way. This approach is shown to be effective even under conditions of fast exchange of the acidic proton on a range of monofunctional models (Me3N and MeNH2, studied by N-14 and N-15 NMR spectroscopy) and some polyfunctional bases (MeCONMe2, MeCSNMe2, 4-aminopyridine, by N-14 and O-17 NMR spectroscopy).