Heterocyclic azo dyestuffs in analytical chemistry. Part II. The ligand properties of 2-(2-pyrimidylazo)-1-naphthol and its sulphonated analogues

Abstract

The preparation, from 2-hydrazinopyrimidine and the respective 1,2-naphthaquinones, of 2-(2-pyrimidylazo)-1-naphthol and its derivatives containing sulphonic acid groups in positions 4 to 8 of the naphthalene ring, respectively, is described. The metal-complexing properties of the dyes have been studied, and they are critically compared with their pyridyl analogues as analytical reagents. The dyes produce larger bathochromic shifts on chelation, and form complexes of lower stability. These two facts indicate that the dyes should be capable of higher selectivity than their pyridyl analogues. They are found to be better indicators for the titration of copper and better chromatographic spray reagents than their pyridyl analogues.