Reactions of Aldehydes and Ketones 3

The Retro-Aldol Reaction
With ketones, the addition step leading to the aldol is unfavorable due to steric hindrance,
and the equilibrium favors the aldol precursors rather than the addition product.
However, dehydration of the aldol addition product can draw the equilibrium toward completion, whether the reactant is an aldehyde or a ketone. Enolate additions to both aldehydes and ketones are also feasible when a stronger base (such as LDA) is used in an aprotic solvent.
Because the steps in an aldol addition mechanism are readily reversible, a retro-aldol reaction can occur that converts a ?-hydroxy aldehyde or ketone back to the precursors of an aldol addition.

The Retro-Aldol Reaction
With ketones, the addition step leading to the aldol is unfavorable due to steric hindrance,
and the equilibrium favors the aldol precursors rather than the addition product.
However, dehydration of the aldol addition product can draw the equilibrium toward completion, whether the reactant is an aldehyde or a ketone. Enolate additions to both aldehydes and ketones are also feasible when a stronger base (such as LDA) is used in an aprotic solvent.
Because the steps in an aldol addition mechanism are readily reversible, a retro-aldol reaction can occur that converts a ?-hydroxy aldehyde or ketone back to the precursors of an aldol addition.