Adipic Acid: Cyclohexanol Oxidised with Boiling Nitric Acid, 1925

Cyclohexanol dripped slowly into boiling concentrated nitric acid is oxidised to adipic acid, which crystallizes when the liquid cools (Organic Syntheses, 1925: 500 g cyclohexanol gives 375–386 g). The acid must already be boiling, or unreacted cyclohexanol can explode. Adipic acid is half of nylon 66. The picture: our diagram of the four stages.