Tautomerism in 1-phenylazo-2-naphthols by use of nitrogen-14 nuclear magnetic resonance data

Abstract

Nitrogen-14 double-irradiation techniques have been used to detect coupling between the labile proton and the nitrogen nucleus α to the phenyl ring in 1-phenylazo-2-naphthols. The ¹⁴N chemical shift of the nitrogen nucleus concerned has been measured for various substituents on the phenyl ring. Quantitative estimates of the amounts of hydroxyazo- and hydrazone tautomers have been obtained. The factors governing the observed errors associated with the ¹⁴N chemical shift measurements have been discussed.