Tropone

Tropone or 2,4,6-cycloheptatrien-1-one is an organic compound with some importance in organic chemistry as a non-benzenoid aromatic. The compound consists of a ring of seven carbon atoms with three conjugated alkene groups and a ketone group. The related compound tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one) has an additional alcohol (or an enol including the double bond) group next to the ketone.

The tropone moiety can be found in biomolecules such as colchicine, stipitatic acid and hinokitiol.

Tropone has been known since 1951 and is also called cycloheptatrienylium oxide. The name tropolone was coined by M. J. S. Dewar in 1945 in connection to perceived aromatic properties.

Properties

Dewar in 1945 proposed that tropones could have aromatic properties. The carbonyl group is polarized with a partial positive charge on the carbon atom (A) and a partial negative charge on oxygen. In an extreme case the carbon atom has a full positive charge (B) forming a tropylium ion ring which is an aromatic 6 electron system (C).