Tropolone

Tropolone is an organic compound with the formula C7H6O2. It consists of a seven-membered ring that bears a ketone carbonyl and an adjacent hydroxyl group, is named systematically as 2-hydroxycyclohepta-2,4,6-trien-1-one. The ring contains a conjugated system and is regarded as a non-benzenoid aromatic compound, reflecting significant delocalization of π electrons despite its unusual ring size.

The molecule features a hydroxy-ketone arrangement that allows tautomeric and resonant stabilization within a cyclic conjugated framework. This contributes to an aromatic-like character and to the relatively high acidity of the hydroxyl proton compared with many other phenolic systems. In basic media, tropolone can form tropolonate anions, which are stabilized by resonance and can act as ligands for metal ions.

Tropolone was named after Tropaeolum, the genus of nasturtium, from which the compound was historically first isolated. It occurs only in trace amounts in some plants and has inspired the development of many derivatives that serve as synthetic building blocks in organic chemistry. Tropolone and its derivatives are also studied as ligands in coordination chemistry and as motifs in natural product synthesis and dye chemistry.

Synthesis of tropolone typically involves constructing the seven-membered ring with the appropriate hydroxy and carbonyl functionalities, followed by controlled oxidation or rearrangements. Several routes have been reported, reflecting its value as a versatile scaffold in chemical research.