Q84 / 240 · KCET 2026 · Chemistry
The compound that does not answer iodoform test is
- AEthanal
- BAcetone
- Correct answerCEthanoic acid
- DAcetophenone
Solution
The iodoform test is given by compounds containing a $CH_3-CO-$ group (methyl ketones and acetaldehyde) or a $CH_3-CH(OH)-$ group (which can be oxidized to a methyl ketone).
Ethanal ($CH_3CHO$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Acetone ($CH_3COCH_3$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Acetophenone ($C_6H_5COCH_3$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Ethanoic acid ($CH_3COOH$) is a carboxylic acid. In the presence of the basic reagent ($NaOH + I_2$), it undergoes an acid-base reaction to form the acetate ion ($CH_3COO^-$), which does not undergo the haloform reaction. Thus, it does not give the iodoform test.
Answer: Ethanoic acid
Ethanal ($CH_3CHO$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Acetone ($CH_3COCH_3$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Acetophenone ($C_6H_5COCH_3$) contains a $CH_3-CO-$ group, hence it gives the iodoform test.
Ethanoic acid ($CH_3COOH$) is a carboxylic acid. In the presence of the basic reagent ($NaOH + I_2$), it undergoes an acid-base reaction to form the acetate ion ($CH_3COO^-$), which does not undergo the haloform reaction. Thus, it does not give the iodoform test.
Answer: Ethanoic acid
Hence, the correct answer is option: 'C'.