Visible absorption spectra of some novel heteroarylazo disperse dyes derived from 2-hydroxy-1,4-naphthoquinone

Synthesis of eight novel heteroarylazonaphthoquinone dyes has been carried out by diazotisation of a range of heterocyclic amines in nitrosyl sulphuric acid and coupling these on to 2‐hydroxy‐1,4‐naphthoquinone. The dyes have been characterised by elemental analysis and spectroscopic methods. The effect on the visible absorption spectrum of the substituents present, and external influences such as solvents, pH and temperature, has been investigated in detail.