Question

Mohler's test is carried out for qualitative test of.......

• A. Sulfur dioxide
• B. Sorbic acid
• C. Benzoic acid
• D. Barium chloride

Hint:

Mohler's test relies on the nitration of the benzene ring of benzoic acid to form dinitro derivatives.
Think of "M" in Mohler linking to the "meta" position of dinitrobenzoic acid to help remember this reaction.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The detection of chemical preservatives in food products is crucial for maintaining food safety and regulatory compliance.
Key Principle:
Mohler's test is a classic qualitative colorimetric reaction used specifically to identify benzoic acid in various food matrices.

Step 2: Detailed Explation:
Benzoic acid ($C_6H_5COOH$) is a widely used chemical preservative, especially in high-acid foods like squashes, carboted beverages, and fruit jams.
In Mohler's test, benzoic acid is first extracted from the acidified food sample using an organic solvent like ether or chloroform.
The extracted residue is then treated with a mixture of concentrated sulfuric acid and potassium nitrate (or nitric acid) to undergo nitration.
This nitration reaction converts benzoic acid primarily into meta-dinitrobenzoic acid.
Upon addition of ammonium sulfide, the dinitro compound is reduced to form an ammonium salt of diaminobenzoic acid.
This reaction produces a characteristic brownish-red or reddish-brown color, which turns to a violet-red color when heated.
This color change serves as positive confirmation of the presence of benzoic acid.
Sulfur dioxide is usually alyzed using the Monier-Williams method, and sorbic acid is often detected using thiobarbituric acid reactions.

Step 3: Fil Answer
Consequently, Mohler's test is carried out for the qualitative detection of benzoic acid.