Key Idea : Aldehydes or ketones with α-H atom, in presence of dilute base, undergoes aldol condensation to give β-hydroxy aldehyde or β-hydroxy ketone. On heating, aldols eliminate water molecule to form α,β-unsaturated compound. 
Note: When aldehydes condense with ketones, it is the α⋅H of ketone which takes part in condensation. This reaction is called crossed aldol condensation.



