MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

The iodoform test is given by compounds containing either a methyl ketone group (CH_3-CO-) or a secondary alcohol group with a terminal methyl (CH_3-CH(OH)- group), as well as ethanol and acetaldehyde. Ethyl methyl ketone (CH_3-CO-CH_2-CH_3) contains a CH_3-CO- group, so it gives a positive iodoform test. Isopropyl alcohol (CH_3-CH(OH)-CH_3) contains a CH_3-CH(OH)- group, so it gives a positive iodoform test. 3-Methyl-2-butanone (CH_3-CO-CH(CH_3)_2) contains a CH_3-CO- group, so it gives a positive iodoform test. Isobutyl alcohol ((CH_3)_2CH-CH_2-OH) is a primary alcohol (other than ethanol) and does not contain a CH_3-CH(OH)- group. Upon oxidation, it forms isobutyraldehyde, which lacks a CH_3-CO- group. Therefore, it does not give the iodoform test. Answer: Isobutyl alcohol