A diabetic person's exhaled breath contains propanone. A student tries to test the diabetes by asking the person to bubble the reagent with his exhaled breath. Which of the following reagents would give a positive result?
Correct answer: D. Alkaline aqueous iodine
- A. Aqueous Bromine
- B. Fehling's reagent
- C. Tollen's reagent
- D. Alkaline aqueous iodine
Explanation
Propanone (also known as acetone) is a ketone that is often produced in the breath of diabetic patients. It can be detected using a variety of tests, including the reaction with alkaline aqueous iodine. When propanone is added to alkaline aqueous iodine, the iodine is reduced to iodide ion, and the propanone is oxidized to form a yellow-brown precipitate of triiodomethane (also known as iodoform). This reaction is commonly used to test for the presence of ketones in a sample.
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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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