Question

Which of the following gives positive $\text{Tollen's}$ test ?

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

$\text{Tollen's}$ test is specific to aldehydes and is generally not influenced by other functional groups like alcohols or ethers present on the aromatic ring.

Answer 1

The Correct Option is C

The Tollen's test is a chemical reaction used to distinguish between aldehydes and ketones. Aldehydes reduce Tollen's reagent, which is an ammoniacal silver nitrate solution, resulting in the deposition of metallic silver and the formation of a silver mirror on the inner walls of the test tube. Ketones generally do not give a positive Tollen’s test, with some exceptions such as alpha-hydroxy ketones.

Let's analyze each option to determine which one will give a positive Tollen's test:

1. Option 1: The compound contains an ether group and does not have an aldehyde or an alpha-hydroxy ketone functional group. Therefore, it will not give a positive Tollen’s test.
2. Option 2: The compound contains a ketone group but lacks the alpha-hydroxy substituent needed for a positive Tollen’s test. Hence, it will not give a positive test.
3. Option 3: The compound contains an aldehyde group. Aldehydes are well-known for giving a positive Tollen’s test. Therefore, this compound will give a positive Tollen's test, confirming it as the correct answer.
4. Option 4: Similar to option 1, this compound contains an ether group and does not have an aldehyde or alpha-hydroxy ketone functional group, resulting in a negative Tollen’s test.

From the analysis, we conclude that option 3 will give a positive Tollen's test as it contains the necessary aldehyde group.