Preparation of a diazo dye

Diazo dyes are brightly coloured compounds formed in a coupling reaction with unstable benzenediazonium compounds. These are made by the reaction between a phenylamine, sodium nitrite and hydrochloric acid at a temperature under 10ºC (they decompose above this temperature):


Benzenediazonium chloride can couple to other arenes like naphthalen-2-ol. HCl is formed and the phenol group is unaffected. In the practical we use ethyl 4-aminobenzoate in place of phenylamine. Work out the structure of the benzenediazonium chloride formed and suggest a formula for the diazo dye formed by the coupling with naphthalen-2-ol. Check your answers here.

Video - preparation of a diazo dye