Recall that the aldol addition reaction is unfavorable for ketones under basic conditions. The retro-aldol reaction is the exact reverse of the aldol addition, where the β-hydroxy ketone in the presence of an aqueous base is preferably cleaved into two ketone molecules as the retro-aldol products. The reaction mechanism consists of three distinct steps. In step one, the deprotonation of the β-hydroxy group generates an alkoxide ion intermediate. In the following step, the alkoxide's carbon–carbon bond is cleaved to form an enolate ion and a ketone molecule. In the final step, the protonation of the enolate ion produces the second ketone molecule. Similarly, the β-hydroxy aldehyde undergoes the retro-aldol reaction yielding the corresponding carbonyl precursors.