Question

Formation of aldol products from carbonyl compounds is the result of an equilibrium reaction. Write the reaction for acetone, excluding dehydration, a case in which the equilibrium does not favor the aldol condensation. Discuss why product formation is more unfavorable than the condensation of acetaldeyde and suggest experimental approaches on how the equilibrium can be readjusted to produce a reasonable amount of aldol condensation product.

Answer 1

The self-aldolization of Acetones is usually slow & reversible and the equilibrium constant for aldol formation is often unfavorable. Only after dehydration does the reaction become thermodynamically favorable. Because  Ketones such as acetones are much less acidic than aldehydes. Because of this reversibility, the yield of aldol products is related to their relative thermodynamic stability

A clever way of overcoming this disadvantage has been found. A comparatively insoluble base, Ba(OH)₂, is used to catalyze the aldol reaction of acetone, and the product is removed from contact with this base by filtration and recirculation of the acetone.

In the case of aldehyde reactants the aldol reaction is modestly exothermic and the yields are good because of their acidity.