{{short description|Functional group >C(OH)O– on a cyclic compound}} [[File:Lactol group in ribose.png|thumb|right|120px|The lactol functional group, highlighted in blue, is present in many sugars such as ribose shown here.]]
In organic chemistry, a '''lactol''' is a functional group which is the cyclic equivalent of a hemiacetal ({{chem2|\sCH(OH)O\s}}) or a hemiketal ({{chem2|>C(OH)O\s}}). The compound is formed by the intramolecular, nucleophilic addition of a hydroxyl group ({{chem2|\sOH}}) to the carbonyl group ({{chem2|C\dO}}) of an aldehyde ({{chem2|\sCH\dO}}) or a ketone ({{chem2|>C\dO}}).<ref>IUPAC Gold Book [http://goldbook.iupac.org/L03438.html lactols]</ref>
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. :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:<ref>{{cite journal|title=Oxidation, reduction and deoxygenation of carbohydrates |author=Lundt, Inge |journal=Glycoscience |year=2001 |issue=1 |pages=501–531}}</ref> * 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
==References== {{Reflist}}
Category:Functional groups Category:Lactols