Aldolkondensasjon

Aldolkondensasjon is a fundamental organic reaction that involves the joining of two carbonyl compounds, typically aldehydes or ketones. This reaction occurs in the presence of a base or acid catalyst and results in the formation of a beta-hydroxy carbonyl compound, which can then undergo dehydration to form an alpha,beta-unsaturated carbonyl compound.

The first step of the aldol condensation is the deprotonation of an alpha-hydrogen atom from one of the carbonyl compounds by the base or acid catalyst, forming a resonance-stabilized enolate anion. This enolate anion then acts as a nucleophile and attacks the electrophilic carbonyl carbon of a second molecule of the aldehyde or ketone. This nucleophilic addition forms an alkoxide intermediate.

In the presence of a base, the alkoxide intermediate is protonated by water or another protic solvent to yield the beta-hydroxy carbonyl compound, also known as the aldol addition product. This aldol addition product can then undergo a dehydration step, typically promoted by heat or a stronger acid/base, where a molecule of water is eliminated. The elimination occurs between the alpha and beta carbons, forming a carbon-carbon double bond. This results in the formation of an alpha,beta-unsaturated aldehyde or ketone, which is the aldol condensation product.

Aldol condensations are versatile and widely used in organic synthesis to create new carbon-carbon bonds, which are essential for building complex organic molecules. The reaction can be controlled to favor either the addition product or the condensation product by adjusting reaction conditions.