Concept:To distinguish between a pure alcohol (a diol) and an alcohol that also contains an aldehyde group, we need a reagent that reacts exclusively with one functional group.
Solution:- The first compound is 1,2-butanediol (contains only hydroxyl groups).
- The second compound is 2-hydroxybutanal (contains a hydroxyl group AND an aldehyde group).
- 2,4-DNPH reacts specifically with carbonyl compounds (aldehydes and ketones) to form brightly colored hydrazone precipitates.
- Therefore, 2,4-DNPH will react with the second compound (forming a precipitate) but will not react with the first compound.
Why other options are incorrect:Strong oxidizers like Potassium manganate would oxidize both compounds. Dilute acid will not yield a clear visual discriminatory reaction. Sodium nitroprusside is used for methyl ketones, not aldehydes.
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