Lactol

In organic chemistry, a lactol is the functional group formed by the intramolecular nucleophilic addition of a hydroxyl group to an aldehyde. A lactol is the cyclic equivalent of a hemiacetal.

A lactol is often found as an equilibrium mixture with the corresponding hydroxyaldehyde. The equilibrium can favor either direction depending on ring size and other conformational effects.
 * [[Image:lactol equilibrium.png|300px|left]]

The lactol functional group is prevalent in nature as component of aldose sugars.

Chemical reactivity
Lactols can participate in a variety of chemical reactions including:
 * Oxidation to form lactones
 * Reaction with alcohols to form acetals
 * The reaction of sugars with alcohols or other nucleophiles leads to the formation of glycosides
 * Reduction (deoxygenation) to form cyclic ethers