Hydroxyaldehyde

Hydroxyaldehyde refers to any organic compound that contains both an aldehyde group (-CHO) and one or more hydroxyl groups (-OH) in the same molecule. The class includes compounds in which the hydroxyl is located at different positions along the carbon chain, giving rise to subclasses such as alpha-hydroxy aldehydes (OH on the carbon next to the formyl carbon) and beta-hydroxy aldehydes (OH on the second carbon away). The simplest example is glycolaldehyde, systematic name 2-hydroxyethanal, with the structure HO-CH2-CHO. Another well-known member is glyceraldehyde, or 2,3-dihydroxypropanal, a triose sugar that exists as several stereoisomers.

Hydroxyaldehydes occur naturally as intermediates in carbohydrate metabolism and in the oxidative degradation of sugars. They can be prepared synthetically by partial oxidation of polyols or by periodate cleavage of vicinal diols, among other methods. Many hydroxyaldehydes are reactive and may exist in equilibrium with cyclic hemiacetals in solution, especially under acidic or basic conditions, and some are prone to polymerization or further oxidation.

Chemically, the aldehyde group makes hydroxyaldehydes susceptible to oxidation to hydroxyacids and to reductions to corresponding hydroxy alcohols. The hydroxyl group provides additional reactivity, enabling intramolecular hemiacetal formation or reactions typical of alcohols, such as esterification or ether formation. Because of their dual functionality, hydroxyaldehydes are important as intermediates in organic synthesis and carbohydrate chemistry; they are also encountered as intermediates in biological pathways and as fragments in flavor and fragrance chemistry.