A compound is heated with zinc dust and ammonium chloride followed by addition of the Tollen's reagent. Formation of silver mirror indicates the presence of following group

Options

A. `-CHO`
B. `-overset(O)overset(||)(C )-`
C. `-NO_(2)`
D. `-NH_(2)`

Answer

To solve the question, we need to analyze the chemical reactions involved when a compound is heated with zinc dust and ammonium chloride, followed by the addition of Tollen's reagent. The formation of a silver mirror indicates the presence of a specific functional group in the compound.

### Step-by-Step Solution:

1. **Identify the Reagents**: The compound is treated with zinc dust and ammonium chloride. This combination is known to reduce nitro compounds.

**Hint**: Think about what zinc dust and ammonium chloride do in organic reactions.

2. **Reaction with Nitro Compounds**: When nitro compounds (RNO2) are heated with zinc dust and ammonium chloride, they are reduced to hydroxylamines (R-NH2OH). This is a crucial step as it indicates the presence of a nitro group in the original compound.

**Hint**: Recall the reduction process of nitro groups and what they convert into.

3. **Addition of Tollen's Reagent**: After the formation of hydroxylamines, the next step is the addition of Tollen's reagent (ammonical silver nitrate). Hydroxylamines can further react with Tollen's reagent.

**Hint**: Consider how Tollen's reagent interacts with different functional groups.

4. **Formation of Silver Mirror**: The reaction of hydroxylamines with Tollen's reagent results in the oxidation of hydroxylamines to nitroso compounds (R-NO). During this reaction, silver ions (Ag+) are reduced to metallic silver, leading to the formation of a silver mirror.

**Hint**: Think about the significance of silver mirror formation in identifying functional groups.

5. **Conclusion**: Since the entire process indicates the presence of a nitro group (NO2) in the original compound, we conclude that the formation of a silver mirror confirms the presence of the nitro group.

**Final Answer**: The presence of the nitro group (NO2) is indicated by the formation of a silver mirror when the compound is treated with zinc dust, ammonium chloride, and Tollen's reagent.

### Summary:
The correct answer is the presence of the nitro group (NO2) in the compound, as evidenced by the formation of a silver mirror after the reaction with Tollen's reagent.