Diketone

A diketone is a molecule containing two ketone groups. The simpliest diketone is diacetyl, also known as 2,3-butanedione. 2,3-Butanedione, acetylacetone, and hexane-2,5-dione are examples of 1,2-, 1,3-, and 1,4-diketones, respectively. Dimedone (5,5-dimethyl-1,3-cyclohexanedione, CAS registry number 126-81-8), is an example of a cyclic diketone.

Reactions
1,3-Diketones, such as acetylacetone, are particularly prone to form stable enols or enolates because of conjugation of the enol or enolate with the other carbonyl group, and the stability gained in forming a six-membered ring, (hydrogen bonded in the case of the enol or containing the counter ion in the case of the enolate).



The conjugate base derived from 1,3-ketones form complexes with metal ions.

Diketones with one or two methylene groups separating the carbonyl groups typically coexist with their enol tautomers. The reactions of such dicarbonyls are very similar to those of simple ketones.

EU Regulation
The EU Commission has declared that diketones (for example acetylacetone, CH3COCH2COCH3) are like dialcohols and hydroxyketones in that they are in vitro and in vivo genotoxic chemical substances and therefore have been forbidden as nutrition additives since 2005.

As Diacetyl is a diketone (in fact the simplist) it may be eventually subject to this EU regulation.