From the self-condensation of acetaldehyde under basic aldol conditions, which compound is formed by dehydration of the aldol product?

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Multiple Choice

From the self-condensation of acetaldehyde under basic aldol conditions, which compound is formed by dehydration of the aldol product?

Under basic aldol conditions, acetaldehyde forms an enolate that adds to another acetaldehyde molecule, giving a β-hydroxyaldehyde. The product is 3-hydroxybutanal, with the new bond between the α-carbon of one acetaldehyde and the carbonyl carbon of the other. When this aldol product undergoes dehydration, water is removed to form a double bond between the α and β carbons, producing an α,β-unsaturated aldehyde: crotonaldehyde (CH3-CH=CH-CHO). This conjugation with the aldehyde makes the dehydration favorable. The other options are simply not the dehydrated aldol product from acetaldehyde self-condensation. Crotonaldehyde is the dehydration product of the β-hydroxyaldehyde formed in the aldol step.

Under basic aldol conditions, acetaldehyde forms an enolate that adds to another acetaldehyde molecule, giving a β-hydroxyaldehyde. The product is 3-hydroxybutanal, with the new bond between the α-carbon of one acetaldehyde and the carbonyl carbon of the other.

When this aldol product undergoes dehydration, water is removed to form a double bond between the α and β carbons, producing an α,β-unsaturated aldehyde: crotonaldehyde (CH3-CH=CH-CHO). This conjugation with the aldehyde makes the dehydration favorable.

The other options are simply not the dehydrated aldol product from acetaldehyde self-condensation. Crotonaldehyde is the dehydration product of the β-hydroxyaldehyde formed in the aldol step.

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