Question

What of the following compounds, on being warmed with iodine solution and NaOH gives iodoform test?
This question has multiple correct options.
(a) $C{{H}_{3}}C{{H}_{2}}OH$
(b) $C{{H}_{3}}OC{{H}_{3}}$
(c) $C{{H}_{3}}-CH(OH)-C{{H}_{3}}$
(d) $C{{H}_{3}}OH$

Answer 1

Hint: iodoform is there test performed in the laboratories to identify the carbonyl compounds and this test is given only by those compounds only which consists of the methyl group attached to the alpha carbon and ketones containing the methyl groups.

Complete step by step solution:
- First of all, we should know what an iodoform test is. In this test, when the iodine and sodium hydroxide are added to the compounds , pale yellow color precipitates of iodoform are formed This test is given by the compounds such as Acetaldehyde, Methyl Ketones , Ethanol and the secondary alcohols which contains the methyl Groups attached to the alpha carbon.
- The reaction of iodine and the sodium hydroxide with methyl ketone gives yellow precipitate along with an antiseptic smell.
- This test is given by only carbonyl compounds and thus, is used to distinguish between the aldehydes and the ketones. If an aldehyde gives the positive iodoform test then, it is only acetaldehyde because it contains the alkyl group attached to the alpha carbon
- So, thus from the above given all the compounds all given the iodoform tests i.e. $C{{H}_{3}}C{{H}_{2}}OH$ ,$C{{H}_{3}}OC{{H}_{3}}$ and $C{{H}_{3}}-CH(OH)-C{{H}_{3}}$ gives iodoform tests as they contain the alkyl group attached to alpha carbons and ketone group.
But $C{{H}_{3}}OH$ doesn’t give this test as it doesn’t contain any methyl group attached to the alpha carbon and thus, doesn’t give positive iodoform test.

Hence, options (a),(b) and (c) are correct.

Note: this iodoform test is not given by the tertiary alcohols as it doesn’t have any hydrogen atom attached to the carbon which is attached to the functional group -OH and thus, doesn’t give this iodoform reaction