Diketones
A diketone is an organic chemical compound that contains two carbonyl groups and has the general structure RC (= O) –X – C (= O) –R ', where R, R' and X are carbon-containing radicals. The simplest diketones are diacetyl (H 3 C-CO-CO-CH 3 ), acetylacetone (H 3 C-CO-CH 2 -CO-CH 3 ) and acetonylacetone (H 3 C-CO-CH 2 -CH 2 -CO -CH 3 ). Diketones are formed by the oxidation of diols or hydroxy ketones .
Systematics
The distance between the carbonyl functions divides the diketones into several classes. α-Diketones such as diacetyl have vicinal carbonyl groups. In the case of β-diketones, the carbonyls are separated by a methylene group ; Due to the strong electron-withdrawing effect of the carbonyls, the two hydrogen atoms on the methylene group between the two carbonyl groups are acidic (ie easily split off under the influence of a base), this is an example of CH acidity . In particular, diketones are often referred to with the suffix -dion .
Reactions
Many reactions of diketones correspond to those of ketones . The reactivity and reaction behavior differ depending on the distance between the keto groups.
1,3-Diketones can easily enolize and form thermodynamically stable enols, e.g. B. Acetylacetone is 80% in the liquid state in the enol form.
Nucleophilic addition reaction
Diketone + nucleophile → tetrahedral carbonyl addition component
- Diketones + alcohol + acid or base ↔ hemiacetal
health
In May 2005 the EU Commission declared that the diketone acetylacetone ( pentane-2,4-dione ) is a genotoxic chemical substance in vitro and in vivo and is therefore prohibited as a food additive.
literature
- Beyer / Walter : Textbook of Organic Chemistry , 19th edition, S. Hirzel Verlag, Stuttgart 1981, ISBN 3-7776-0356-2 , pp. 301-303.