The document discusses aldol condensation, a base-catalyzed reaction where an aldehyde or ketone with an alpha hydrogen reacts with another aldehyde or ketone. This doubles the number of carbon atoms and forms an aldol (β-hydroxy aldehyde or ketone) product. The reaction mechanism involves the base abstracting the alpha hydrogen to form a carbanion, which then attacks the carbonyl carbon of another molecule to form an alkoxide intermediate. This intermediate then protonates to form the aldol product, which can sometimes lose water to form an alpha,beta-unsaturated aldehyde. Examples are given of reactants that can and cannot undergo aldol condensation, and students are asked to predict products