Question

What is the product of a mixed aldol condensation between p-tolualdehyde (C8H8O) and acetone?

Answer 1

The major product should be (`E,E`)-bis(4-methylbenzylidene)acetone.

Explanation:

The aldol condensation involves attack of an enolate ion on the base of a carbonyl compound to form a β-hydroxycarbonyl compound (an aldol).

(from www.chem.ucla.edu)

The aldol can then dehydrate to form an α,β-unsaturated carbonyl compound.

The process requires an active methylene adjacent to a carbonyl group.

If there are two active methylenes, the condensation can occur on each side of the carbonyl group.

For example, benzaldehyde reacts with acetone to give dibenzalacetone.

By analogy, I predict that 4-methylbenzaldehyde will react with acetone to form (`E,E`)-bis(4-methylbenzylidene)acetone.

The major product should be the more stable `E,E` isomer.