Hydroxyketones

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α-Hydroxyketone with a hydrogen bond
Diacetone alcohol, a β-hydroxy ketone

Hydroxy ketones (also called ketols or keto alcohols ) are organic compounds that contain a keto group and a hydroxyl group . The positional distance is identified with Greek letters as locant .

  • In the alpha position, the carbonyl group and the carbon atom bearing the hydroxyl group are directly adjacent. These α- hydroxyketones are also called acyloins (e.g. acetoin or benzoin ). One of the possible methods of representing acyloins is the acyloin condensation or benzoin addition . Here, R 1 = R 2 (the radicals R 1 and R 2 are either an alkyl radical or an aryl radical ). As a result of the ketol-enediol tautomerism , acyloins are good reducing agents.
  • In the beta position there is another carbon atom between the functional groups . β-Hydroxyketones are, inter alia, reaction products of the aldol addition of ketones. This includes B. Diacetone alcohol , which is formed by aldol addition of acetone . β-Hydroxyketones tend to split off water and thereby form α, β-unsaturated ketones. Of diacetone alcohol is produced as mesityl oxide . The driving force for this easy elimination is the formation of a conjugated electron system.
  • Fructose (in the open-chain form) is an example of a ketone that simultaneously carries hydroxyl groups in the α, β, γ and δ positions.

If the keto and hydroxy groups are close by, an intramolecular hydrogen bond can form between them, as can be seen in the picture of the α-hydroxy ketone.

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