Under basic conditions, acetaldehyde undergoes an aldol condensation with itself. What is the major dehydrated product?

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Multiple Choice

Under basic conditions, acetaldehyde undergoes an aldol condensation with itself. What is the major dehydrated product?

Explanation:
The reaction showcases an aldol condensation where acetaldehyde forms a β-hydroxyaldehyde first, then loses water to give an α,β-unsaturated aldehyde. The enolate of one acetaldehyde attacks another, producing 3-hydroxybutanal. Under basic conditions, this β-hydroxyaldehyde dehydrates to create an α,β-unsaturated aldehyde that is conjugated with the aldehyde group. The most stable dehydrated product is crotonaldehyde (trans-2-butenal) because the conjugated system is preferred, and the trans geometry minimizes steric hindrance while maximizing conjugation. The dehydration product is not the aldol adduct itself and not a diene or the starting aldehyde.

The reaction showcases an aldol condensation where acetaldehyde forms a β-hydroxyaldehyde first, then loses water to give an α,β-unsaturated aldehyde. The enolate of one acetaldehyde attacks another, producing 3-hydroxybutanal. Under basic conditions, this β-hydroxyaldehyde dehydrates to create an α,β-unsaturated aldehyde that is conjugated with the aldehyde group. The most stable dehydrated product is crotonaldehyde (trans-2-butenal) because the conjugated system is preferred, and the trans geometry minimizes steric hindrance while maximizing conjugation. The dehydration product is not the aldol adduct itself and not a diene or the starting aldehyde.

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