Question

Schiff’s reagent is:
(A) P- Rosaline hydrochloride solution decolorized with sulphurous acid
(B) Magenta solution decolorized with ${\text{C}}{{\text{l}}_{\text{2}}}$
(C) Ammoniacal silver nitrate solution
(D) Alkaline ${\text{KMn}}{{\text{O}}_{\text{4}}}$ solution

Answer 1

To answer this question, you must recall the various organic reagents and their names that are given after their discoverers as a symbol of respect and consideration for their effect. Schiff’s reagent is used in the Schiff’s test for the presence of aldehydes in a given organic sample.

Complete step by step solution
In option A, we have p- Rosaline hydrochloride solution. It is a pink colored solution which is decolorized by sulphur dioxide. This is the Schiff’s reagent and is used for the detection of carbonyl groups, i.e. aldehydes and ketones. Aliphatic aldehydes give the Schiff’s test and they give a red colored precipitate when reacted with P- Rosaline hydrochloride solution. Ketones and aromatic aldehydes do not give this test. Option A is correct.
In option B, the magenta colour of the Schiff’s reagent is discharged in the presence of sulphur dioxide gas or sulphurous acid but not by chlorine gas. Option B is incorrect.
In option C, we have ammoniacal silver nitrate solution. This is known as the Tollen’s reagent. It is used as a confirmatory test for aldehydes but ketones do not give this test. The appearance of a silver mirror on the walls of the test tube is observed.
In option D, we have alkaline potassium permanganate solution. It is known as the Baeyer's reagent. It is a pink colored solution and its colour is discharged in the presence of alkenes and alkynes.
The correct answer is A.

Note
Care should be taken that Schiff’s base is not confused with Schiff’ reagent. Schiff’s base is a substituted imine and formed by the reaction of carbonyl compounds with primary amine.