Question

Iodoform test is not answered by:
(A) ${{C}_{2}}{{H}_{5}}OH$
(B) $C{{H}_{3}}OH$
(C) $C{{H}_{3}}COC{{H}_{3}}$
(D)

Answer 1

Hint: As we must know, iodoform is a qualitative test and is used for the detection of ketones and aldehyde having an alpha methyl group. Now, by using this information we can answer the given question.

Complete answer:
- Iodoform is the organic iodine compound with the formula, $CH{{I}_{3}}$. It is a pale-yellow, crystalline and volatile compound.
- Iodoform test is used for the detection of ketones and aldehydes having an alpha methyl group. Alpha means that it is directly attached to the carbon with the functional group.
- The reagents used are iodine and sodium hydroxide (NaOH).
- When these two reagents are added to the compound containing ketone or aldehyde with alpha methyl group, a pale-yellow precipitate of iodoform is formed.
- This test can also be used to identify alcohols. Tertiary alcohol does not give this test as it cannot be oxidised. In case of primary alcohol, only ethanol gives this test. All secondary alcohols show positive results to this test, as they are oxidised to ketones.
- Now coming to the question, it is safe to say that option (A), (C), and (D) will give iodoform test but option (B) will not give iodoform test as it is primary alcohol.

Therefore, the answer to the question is (B) $C{{H}_{3}}OH$.

Note: Amongst all primary alcohols, ethane is the only aldehyde which gives iodoform test. Also, this test takes place in basic medium since this leads to the formation of carbanion.