Question

When alcoholic solution of an organic compound is treated with few drops of Schiff's reagent, pink colour appears. This confirms the presence of group

• A. $-\text{COOH}$
• B. $-\text{CHO}$
• C. $-\text{SO}$
• D. $-\text{CH}_2\text{OH}$

Hint:

Schiff's test is a standard diagnostic test used to differentiate aldehydes from ketones. Remember: Aldehydes give a swift positive pink/magenta result, while ketones do not!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks us to identify the functional group that gives a characteristic pink or magenta color development when reacted with Schiff's reagent.

Step 2: Detailed Explanation:
Schiff's reagent is a solution of rosaniline hydrochloride (fuchsine) that has been decolorized by sulfur dioxide. It acts as a highly sensitive qualitative test for aldehydes. When an aliphatic or aromatic aldehyde ($-\text{CHO}$ group) is added to this colorless reagent, it restores the magenta-pink color due to the formation of a complex quinoid dye structure. Ketones, carboxylic acids ($-\text{COOH}$), and alcohols ($-\text{CH}_2\text{OH}$) generally do not restore the color of Schiff's reagent under standard test conditions. Thus, the appearance of the pink color specifically confirms the presence of an aldehydic group.

Step 3: Final Answer:
The functional group confirmed by the Schiff's test is the aldehyde group ($-\text{CHO}$), matching option (B).