n.
Any member of a class of cyclic organic compounds comprising a six-membered unsaturated ring (see saturation ) to which two oxygen atoms are bonded as carbonyl groups ( 2015; C 003D; O; see functional group ).
This structure plays an important role in theories of chemical structure and colour, since quinones occur as pigment s in bacteria, fungi, and certain higher plants; animals containing quinones obtain them from plants they eat. The K vitamins (see vitamin K ) are naphthoquinones. The term quinone often specifically denotes p a r a -benzoquinone (C 6 H 4 O 2 ), a bright yellow solid with a sharp odour used in manufacturing dyes and fungicides and in photography.