Which of the following do not give aldol condensation reactions ?
Correct answer: A. formaldehyde
- A. formaldehyde
- B. acetaldehyde
- C. diemthyl ketone
- D. propionaldehyde
Explanation
Aldol condensation requires an alpha hydrogen to form an enolate or enol, but formaldehyde has no alpha carbon and therefore cannot undergo this reaction. Acetaldehyde, propionaldehyde and dimethyl ketone all have alpha hydrogen atoms, so choosing one of them reflects overlooking this requirement.
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About Reactivity of Aldehydes and Ketones
The polar carbonyl group makes aldehydes and ketones undergo nucleophilic addition, reduction and condensation reactions. Aldehydes are generally more reactive and oxidise readily to carboxylic acids, whereas ketones resist mild oxidation; reactions with hydrogen cyanide, sodium bisulfite and 2,4-DNP help identify their behaviour.
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