User:TaroToro/Aldol



In organic chemistry, an aldol describes a structural motif consisting of a 3-hydroxy ketone or 3-hydroxyaldehyde. An aldol consisting of a 3-hydroxy ketone is called a β-hydroxy ketone, and an aldol consisting of a 3-hydroxy aldehyde is called a β-hydroxy aldehyde. Aldols are usually the product of aldol addition. When used alone, the term "aldol" may refer to 3-hydroxybutanal.

Properties
Aldols derived from aldehydes (β-hydroxy aldehyde) have higher boiling points than its equivalent saturated compound. This is because aldols have a hydroxyl group (-OH) and a carbonyl group (C=O) that allows for hydrogen bonding, while the saturated compound lacks the hydroxyl group.

Stereochemistry
Despite having only two functional groups, many aldols can have complicated structures arising from the relative positions of the OH group and the substituent between it and the carbonyl. Controlling reactions in order to favor the formation of one of these isomers is of great interest in the area of asymmetric synthesis.

Reactions
The chemistry of aldols is dominated by one reaction, dehydration:

RC(O)CH2CH(OH)R' → RC(O)CH=CHR' + H2O

At room temperature, aldols release water.
 * Dehydration of aldols.jpg

Applications
When two molecules of aldehydes react to form an aldol (β-hydroxy aldehyde), the aldol usually produces secondary compounds since it is unstable. Secondary compounds can be diols, unsaturated aldehydes, or alcohols. This is an example of intermolecular addition.

Aldols can be used as starting materials. 3-hydroxybutanal can synthesize quinaldine, which is used to make dyes such as quinoline Yellow SS.

Aldols are also used as intermediates in the synthesis of natural products and medication. The synthesis of Oseltamivir, an antiviral medicine used to treat the flu, involves the aldol reaction.

The structural motif of aldols is often found in polyketide natural products, which can be used to manufacture antibiotics.

Hydroxypivaldehyde is a rare example of a relatively robust aldol. The chemical structure of hydroxypivaldehyde stays the same even after being distilled because of its bulkiness, making it robust.