A diketone is a molecule containing two carbonyl groups.

A diketone is an oxygen nucleophile.

Reactions

Diketones react similarly to ketones or aldehydes.

They also readily undergo enolization, and many 1,3-diketones are thermodynamically stable as conjugated enols or even enolates. One such is ascorbic acid, which is more stable as an enol(ate) rather than a diketone. The enol group gives off a proton, and the charge of the resulting enolate is delocalized along the ketone-enolate system. This delocalization stabilizes the enolate counterion and makes it less likely to regain the proton, which makes ascorbic acid acidic. Also, if a diketone has ketone carbonyls separated only by one carbon, the alcohol hydrogen in the corresponding enol is hydrogen-bonded to the carbonyl oxygen, giving a six-membered ring (-RC=CH-OH..O=CR-).

Nucleophilic addition

1. diketone + alcohol + acid or base ↔ hemiacetal
   • hemiacetal + alcohol + acid catalyst ↔ acetal + water
   • This is a carbonyl-protecting reaction.

Health

EU Commission has declared (see external link), that diketones (for example Pentan-2,4-dion) 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.

External links

• http://europa.eu.int/eur-lex/lex/LexUriServ/site/en/oj/2005/l_128/l_12820050521en00730076.pdf - EU Commission and Diketones

Ketones

Diketon | Diketonum