Which reagent can be used to distinguish ethanal from propanone?

ASaturated aqueous $NaHSO X_{3}$
BTollens reagent
C2,4-DNP
D $NaOH / I X_{2}$

Answer: B

Both

CH X_{3} CHO

and

CH X_{3} COCH X_{3}

contain the

CH X_{3} CO

group, so both give the iodoform test, both give a 2,4-DNP precipitate and both form bisulphite adducts. Only the aldehyde is oxidised by Tollens reagent, giving a silver mirror. Hence Tollens reagent is the answer.

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