15N, 13C and 1H NMR spectra and azo-hydrazone tautomerism of some phenylazo compounds derived from 1,3- and 1,5-dihydroxynaphthalene

Abstract

Five phenylazo compounds derived from 1,3-dihydroxynaphthalene and 1,5-dihydroxynaphthalene and their 15N isotopomers were prepared by coupling with benzenediazonium salts. The products were as follows: 1-phenylazo-2,4-dihydroxynaphthalene 4, 1,3-bis(phenylazo)-2,4-dihydroxynaphthalene 5, 4-phenylazo-1,5-dihydroxynaphthalene 11, X=H, 2-phenylazo-1,5-dihydroxynaphthalene 12, X=H, and 4-(4-nitrophenylazo)-1,5-dihydroxynaphthalene 13, X=NO 2. 1-Phenylazo-2,4-dihydroxynaphthalene 4 was also prepared by condensation of phenylhydrazine with Lawsone ( 6, 2-hydroxy-1,4-naphthoquinone). The 1H, 13C and 15N NMR spectra of these compounds were measured in hexadeuteriodimethyl sulfoxide. 1H and 13C chemical shifts were assigned using two-dimensional NMR spectroscopy. Azo-hydrazone tautomerism was studied using 13C and 15N chemical shifts. All of the compounds studied exist predominantly or completely in their hydrazone forms.