A pleasant-smelling colourless crystalline compound, C9H6O2, m.p. 70°C. It occurs naturally in tonka (or tonquin) beans, and is synthesized from salicylaldehyde. It forms coumarinic acid on hydrolysis with sodium hydroxide. Coumarin is used in making perfumes, to scent tobacco, and as an anticoagulant in medicine; warfarin is derived from it.