Characterization of para ‐substituted benzamidoximes and benzamidinium salts by 15 N NMR spectroscopy

15 N NMR data for a series of 12 para ‐substituted benzamidoximes and benzamidinium salts were determined in dimethyl sulfoxide. For the amino group of benzamidoximes 1 J (N,H) coupling constants were determined using polarization transfer techniques; the other 15 N atoms were not detectable owing to fast exchange processes and, thus, standard proton noise decoupled spectra had to be measured. The 15 N NMR chemical shifts of the oxime‐type nitrogen atom and the benzamidinium amino group (with two exceptions) correlate with Hammett σ° values ( r 2 >0.95). 15 N NMR shift data are a suitable and sensitive means for characterizing far‐ranging electronic substituent effects in these functional groups. Additionally, 13 C NMR data in dimethyl sulfoxide solution are given. All spectroscopic data will be used for investigations into the mechanisms of the enzymes involved in the metabolic cycle of oxidation and reduction of benzamidines and benzamidoximes. Copyright © 2002 John Wiley & Sons, Ltd.