Hydroquinone: Aniline Oxidised to Quinone and Reduced, Thorpe 1912

Aniline in cold dilute sulfuric acid is oxidised by sodium dichromate to quinone, which sulfur dioxide reduces to hydroquinone; ether extracts it, and it is recrystallised from water with charcoal. Thorpe (1912) gives up to 85 % crude yield. A few ppm of hydroquinone keep vinyl acetate from forming peroxides. The picture: our diagram of the route.