In an aldol reaction, which condition favors self-condensation of acetaldehyde to give 3-hydroxybutanal?

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Multiple Choice

In an aldol reaction, which condition favors self-condensation of acetaldehyde to give 3-hydroxybutanal?

Aldol self-condensation relies on enolate formation under basic conditions and using another molecule of the same aldehyde as the electrophile. A base such as hydroxide abstracts an α-hydrogen from acetaldehyde to form the enolate, which then attacks the carbonyl carbon of another acetaldehyde molecule. This yields the β-hydroxyaldehyde, 3-hydroxybutanal, after workup. Keeping the mixture free of excess electrophile ensures the reaction occurs between acetaldehyde molecules rather than forming crossed aldols with other carbonyl compounds. If you use strong acid instead, enolate formation is not favored and the aldol step is less efficient; high temperature with excess electrophile tends to dehydrate the aldol product or give unwanted products, and no base/missing oxidant prevents enolate formation altogether.

Aldol self-condensation relies on enolate formation under basic conditions and using another molecule of the same aldehyde as the electrophile. A base such as hydroxide abstracts an α-hydrogen from acetaldehyde to form the enolate, which then attacks the carbonyl carbon of another acetaldehyde molecule. This yields the β-hydroxyaldehyde, 3-hydroxybutanal, after workup. Keeping the mixture free of excess electrophile ensures the reaction occurs between acetaldehyde molecules rather than forming crossed aldols with other carbonyl compounds. If you use strong acid instead, enolate formation is not favored and the aldol step is less efficient; high temperature with excess electrophile tends to dehydrate the aldol product or give unwanted products, and no base/missing oxidant prevents enolate formation altogether.

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