The correct answer is Option (4) → Propionaldehyde
A positive iodoform test results in a yellow precipitate of $CHI_3$. It is given by:
- Methyl Ketones: $R-CO-CH_3$
- Acetaldehyde: $CH_3CHO$ (the only aldehyde that reacts)
- Specific Alcohols: Those containing the $CH_3CH(OH)-$ group (like Ethanol or Isopropyl alcohol)
Analysis of the Options
- Acetaldehyde ($CH_3CHO$): It contains the $CH_3CO-$ group. It gives a positive test.
- Isopropyl alcohol ($CH_3CH(OH)CH_3$): It contains the $CH_3CH(OH)-$ group. It gives a positive test.
- Butanone ($CH_3COCH_2CH_3$): It is a methyl ketone ($CH_3CO-$ attached to an ethyl group). It gives a positive test.
- Propionaldehyde ($CH_3CH_2CHO$): This is a three-carbon aldehyde. It does not have a methyl group directly attached to the carbonyl carbon (it has an ethyl group instead). Therefore, it will not give the iodoform reaction.
|
