Which of the following reduces Tollen's reagent ?

Options

A. Acetic acid
B. Citric acid
C. Oxalic acid
D. Formic acid

Answer

To determine which of the given compounds reduces Tollen's reagent, we need to understand the nature of Tollen's reagent and its reactivity with different functional groups.

### Step-by-Step Solution:

1. **Understand Tollen's Reagent**:
Tollen's reagent is an ammoniacal silver nitrate solution, which acts as a mild oxidizing agent. It is specifically known for its ability to reduce aldehydes to their corresponding alcohols while oxidizing itself to metallic silver.

2. **Identify the Functional Group**:
Tollen's reagent can only reduce compounds that contain an aldehyde functional group (-CHO). Therefore, we need to check each of the given options to see if they contain this functional group.

3. **Examine Each Option**:
- **Option 1: Acetic Acid (CH₃COOH)**
- Structure: CH₃-C(=O)-OH
- Acetic acid contains a carboxylic acid group, not an aldehyde group. Therefore, it cannot reduce Tollen's reagent.

- **Option 2: Citric Acid (C₆H₈O₇)**
- Structure: Citric acid has multiple carboxylic acid groups and hydroxyl groups.
- There is no aldehyde group present in citric acid. Thus, it cannot reduce Tollen's reagent.

- **Option 3: Formic Acid (HCOOH)**
- Structure: H-C(=O)-OH
- Formic acid contains an aldehyde group (the carbonyl carbon is bonded to a hydrogen atom). Therefore, it can reduce Tollen's reagent.

4. **Conclusion**:
Among the options provided, only formic acid contains an aldehyde group, which allows it to reduce Tollen's reagent. Thus, the answer is:
- **Answer: Formic Acid (Option 3)**