Question

Which of the following does not show iodoform test?

• A. Ethyl methyl ketone
• B. Isopropyl alcohol
• C. $3$- Methyl– $2$– butanone
• D. Isobutyl alcohol

Answer 1

The correct option is D

Isobutyl alcohol

Explanation for correct option

(d) Isobutyl alcohol

• In the structure of isobutyl alcohol, there is no methyl ketone group and primary alcohol group.
• For the iodoform test to be positive, there has to be either methyl ketone group or primary alcohol group.
• Therefore, isobutyl alcohol doesn't show iodoform test.
• Hence, option (d) isobutyl alcohol is the correct option.

Explanation for incorrect options

(a) Ethyl methyl ketone

• In the above structure of ethyl methyl ketone, there is a methyl ketone group present.
• Therefore, ethyl methyl ketone shows positive iodoform test.

(b) Isopropyl alcohol

• In the above structure of isopropyl alcohol, there is a primary alcohol group present.
• Therefore, isopropyl alcohol shows positive iodoform test.

(c) $3$- Methyl– $2$– butanone

• In the above structure of $3$- Methyl– $2$– butanone, there is a methyl ketone group present.
• Therefore, $3$- Methyl– $2$– butanone, shows positive iodoform test.

Hence, the correct option is (d) isobutyl alcohol.