Which compound gives a positive iodoform test?
Correct answer: B. Propanone
- A. Propanal
- B. Propanone
- C. Benzaldehyde
- D. Methanal
Explanation
The test requires a methyl group attached directly to the carbonyl carbon, and propanone is the simplest methyl ketone, giving the pale yellow precipitate of triiodomethane with iodine in alkali. Ethanal is the only aldehyde that responds, since it too has that methyl group. Propanal, methanal and benzaldehyde all lack the required structure.
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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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679 free Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
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