Amines react with nitrous acid to give diazonium salts. Anilines (aryl amines) are converted to their diazonium salts using nitrous acid. Nitrous acid is used to make diazonium salts from amines. Aromatic hydrazines are prepared by reducing aromatic diazonium salts. Aromatic nitriles are often prepared in the laboratory from the aniline via diazonium compounds. It is also possible to functionalize silicon wafers with diazonium salts forming an aryl monolayer. The reaction of converting primary aromatic amine into diazonium salt is called diazotisation. Via the reaction the diazonium compound with hypophosphorus acid aniline gives benzene. Amines can be converted to diazonium salts, which are then hydrolyzed. Aniline and its ring-substituted derivatives react with nitrous acid to form diazonium salts. He prepared it by reduction of a phenyl diazonium salt using sulfite salts. The process of conversion of primary aromatic amines into its diazonium salt is called diazotization. Hg(II) can be alkylated by treatment with diazonium salts in the presence of copper metal. Several of the Sudan dyes are derived from 2-naphthol by coupling with diazonium salts. The alkyl diazonium salts are of little synthetic importance because they are too unstable.