Diazophenols from the diazotization of aminophenols

2-Diazo-4,6-dinitrophenol (DDNP or DINOL) (53) can be prepared from the diazotization of 2-amino-4,6-dinitrophenol (52) (picramic acid) with nitrous acid the latter is obtained from the selective reduction of picric acid with ammonium sulfide. 2-Diazo-4,6-dinitrophenol (53) is widely used as an initiating charge in detonators and caps. 

Glowiak studied the stability of the four diazophenols (59-62), which he prepared from the diazotization of the corresponding aminophenols. It was noted that (61) and (62) show higher chemical stability than (59) and (60) the latter compounds were postulated to have a quinonoid structure rather than a zwitterionic diazophenol structure. 

---