Baudisch reaction

As described originally by Oskar Baudisch in 1939[1] and further developed by his colleague Cronheim in 1947, benzene, hydroxylamine, and hydrogen peroxide are combined.

Baudisch proposed that the reaction proceeds first via the formation of nitroxyl (HN=O), by the oxidation of hydroxylamine hydrochloride with hydrogen peroxide, possibly catalysed by the cupric ions.

[3] Free nitrosophenols are readily oxidized in air, forming nitrophenols, or catechol and nitrite under more aggressive conditions.

The metal ion binds the nitrosyl group and phenoxy oxygen, directing the reaction to occur ortho instead.

Of the benzene derivatives that do not undergo the Baudisch reaction, aromatic aldehydes tend to form hydroxamic acid or oximes.