Question

Give one chemical test to distinguish between the following pairs of compound:
Acetone and Phenol.

Answer 1

The iodoform test is used to differentiate between an organic compound containing a carbonyl group and a compound that does not have the same. The ketones and aldehydes produce a positive iodoform test and the compound that does not have a carbonyl group gives a negative iodoform test.

Complete step by step answer:
The reaction of carbonyl compounds with iodoform produce a positive iodoform test and the groups such as alcohol do not give a positive iodoform test. Let us determine the test with acetone and phenol separately.
(i) Acetone: When the acetone reacts with iodine solution and an aqueous solution of sodium hydroxide in the presence of a water bath, there is a formation of yellow crystals of iodoform which yields a characteristic odor. The reaction is as follows:
$C{H_3}COC{H_3} + 3{I_2} + 4NaOH \to CH{I_3} + C{H_3}COONa + 3NaI + 3{H_2}O$
Since acetone has a carbonyl group in it; it can give a positive iodoform test. This test is also used to differentiate two compounds on the basis of the fact whether one consists of a carbonyl group and which does not.
(ii) Phenol: The phenol consists of a benzene ring along with an alcohol functional group. When phenol reacts with iodine in presence of a strong base such as sodium hydroxide, it does not yield any yellow crystals of iodoform. The reaction is as follows:
$Ph - OH + 3{I_2} + 4NaOH \to {\rm X}$ (no reaction)

Note:
An acetone is a universal volatile, colorless, flammable organic solvent and is used regularly for cleaning purposes and in regular household works and as a regular solvent in chemical laboratories. A phenol is an aromatic organic white colored crystalline volatile solid and is used mainly for the production of nylon resins and several other synthetic fibers.