Which of the following compounds dose NOT respond positively to the iodoform test ?

Step-by-step solution

The iodoform test is given by compounds containing a methyl ketone group ( CH₃-CO- ) or a secondary alcohol group with a terminal methyl ( CH₃-CH(OH)- ), which gets oxidized to a methyl ketone by the reagent. Acetaldehyde ( CH₃-CHO ) contains a CH₃-CO- group and gives a positive test. Propan-2-ol ( CH₃-CH(OH)-CH₃ ) contains a CH₃-CH(OH)- group and gives a positive test. Propanone ( CH₃-CO-CH₃ ) contains a CH₃-CO- group and gives a positive test. Pentan-3-one ( CH₃-CH₂-CO-CH₂-CH₃ ) does not contain a CH₃-CO- group.