Question

Which of the following cannot be used to distinguish between acetaldehyde and acetone?

• A. Tollen's reagent
• B. Fehling solution
• C. Iodoform test
• D. Both (1) and (2)

Answer 1

Answer: (D)

Both (1) and (2)

Answer 2

Tollen's reagent and Fehling solution are oxidizing agents that react with aldehydes but not with ketones. Acetaldehyde (an aldehyde) will give a positive test (silver mirror with Tollen's, red precipitate with Fehling's), while acetone (a ketone) will not. Therefore, both Tollen's reagent and Fehling solution can be used to distinguish between acetaldehyde and acetone. The iodoform test is positive for compounds with a methyl ketone group ($CH_3CO-$) or those that can be oxidized to it. Acetaldehyde ($CH_3CHO$) and acetone ($CH_3COCH_3$) both give a positive iodoform test, producing a yellow precipitate of iodoform ($CHI_3$). Thus, the iodoform test cannot be used to distinguish between them.