Acetylacetone: metal complexes and keto-enol tautomerism – which tautomer is more/less stable?

Tautomerism is a fundamental concept that studies the transfer of a proton between two constitutional isomers, i.e. keto and enol tautomers, where the enol tautomers are usually less stable than the corresponding carbonyl compound. However, this is not the case with acetylacetone. This article discusses two rapidly inter-converting tautomeric forms of acetylacetone, the archetypal (and now textbook) example of tautomerism in organic chemistry from a thermochemical perspective.