Out of the following compounds, which will give iodoform test

(A)    Isopropyl alcohol

(B)    Isobutyl alcohol

(C)    Secondary butyl alcohol

(D)   Ethyl alcohol

(E)    Acetic acid

Choose the correct answer from the options given below:

A, C, D

The correct answer is option (2) A, C, D.

The iodoform test is used to determine whether a given unknown chemical substance contains carbonyl compounds with an \(α-\)methyl group and the structural formula \((R-CO–CH_3)\) or alcohols with the formula \(R-CH(OH)-CH_3\). Iodine and aqueous sodium hydroxide \((NaOH)\) solution or potassium iodide \((KI)\) and sodium hypochlorite \((NaClO)\) solution can also be used to conduct the test. In the iodoform test, the unknown is let to react with a mixture of excess iodine and sodium hydroxide.

(A) Isopropyl alcohol:

Isopropyl alcohol on oxidation in the presence of chromic acid gives acetone, which gives a positive iodoform test.

(B) Isobutyl alcohol:

Isobutyl alcohol does not have an \(\alpha -methyl\) group so doesn't undergo an iodoform reaction.

(C) Secondary butyl alcohol:

Secondary butyl alcohol undergoes an iodoform test as it has an \(\alpha -methyl\)  group.

(D) Ethyl alcohol:

The only primary alcohol that provides the triiodomethane (iodoform) reaction is ethanol. If ‘R’ is a category of hydrocarbons, you have a secondary alcohol. This answer is provided by tonnes of secondary alcohols, but those that do all have a methyl group with the -OH group attached to the carbon.

(E) Acetic acid :

Acetic acid- acetic acid is a carboxylic acid, that is, it has the \(−COOH\) bond. Due to delocalisation of electrons, there is presence of \(O\) adjacent to carbonyl. Therefore, acetic acid does not give iodoform test.