The Nuclear Magnetic Resonance Spectrum of Feist's Acid

Feist's acid is generally accepted to be either I or II. Cogent evidence in favor of I has been obtained by Ettlinger and his structural assignment has been confirmed by x-ray diffraction analysis. Unequivocal evidence that Feist's acid is I and not II has now been obtained from its nuclear magnetic resonance (NMR) spectrum (Fig. 1) in a solution of excess sodium deuteroxide in heavy water.