A2 Chemistry helpWatch
Which spec are you doing?
Nitrate it (add NO2 group) to make nitrobenzene
Reduce it (so the NO2 group becomes an NH2 group) to form a phenyl amine
Then the NH2 changes into NA+Cl- which I have no idea how but that's the azo dye derivative
Sorry, hope it helps a bit
If you're starting with benzene the diazonium salt is made by nitration (conc. sulfuric and nitric acid) followed by reduction (tin and HCl) to make phenylamine. Then you react phenylamine with nitrous acid (sodium nitrite and HCl) below 5ºC. This makes phenyldiazonium chloride.
A sample of phenol made by allowing the some of the diazonium salt to heat up above can be acylated (AlCl3, ethanoyl chloride) in a Freidel Crafts reaction and then hydrolysed to make the hydroxycarboxylic acid.
This will then react with the diazonium salt to form the azo-dye