can you explain cross aldol condensation and its mechanism ?
Aldol condensation in which two different aldehydes or two different ketones or one aldehyde and one ketone having ?-hydrogen atoms are treated with dilute alkali (NaOH or KOH) to form ?-hydroxy aldehydes or ?-hydroxyketones is known as crossed or mixed aldol condensation. Such condensations can give mixture of four products which are difficult to separate. So, this is of little synthetic value. For example, cross aldol condensation between ethanal and propanal.
Cross aldol condensation is of great synthetic use if one of the carbonyl compounds does not contain ?-hydrogen atoms because then we don 't get mixture of products.For example, ethanal with benzaldehyde.