Antiparasitic nitroimidazoles. Part V. Interpretation of the proton magnetic resonance spectra of olefinic protons by means of additive increments, Hammett correlations, and the effect of lanthanide shift reagents

A number of 2-(substituted styryl)-5-nitro-N-substituted imidazoles possessing antiparasitic activity have been characterised by n.m.r. spectroscopy. A full assignment of the proton resonances has been carried out by use of (i) an additive increment method for chemical shift prediction, (ii) correlations with Hammett substituent constants (σI, σM, σR0), and (iii) quantitative measurements of chemical shifts induced in the title and model compounds by europium shift reagents.