15.14 : C-C 結合の形成: アルドール縮合の概要

Aldol condensation involves an aldol addition reaction followed by dehydration. 

In the aldol addition reaction, two identical aldehydes interact in acidic or basic conditions to form a β-hydroxy aldehyde as the initial product. Here, one aldehyde acts as a nucleophile and the other as an electrophile, creating a new carbon–carbon bond.

The name aldol comes from the presence of both alcohol and aldehyde functional groups — 'ald' representing aldehyde and 'ol' corresponding to alcohol.

Like aldehydes, two identical ketones also undergo an aldol addition reaction generating a β-hydroxy ketone.

The formation of the β-hydroxy carbonyl compound is reversible.

However, under suitable reaction conditions, the β-hydroxy aldehyde and ketone dehydrate to yield an enal and an enone, respectively.

An aldol condensation between two different carbonyl compounds is called a crossed aldol reaction. Such a reaction yields a mixture of products.