Which of the following carboxylic acid undergoes decarboxylation easily ?

Options

A. `C_(6)H_(5)-CO-CH_(2)-COOH`
B. `C_(6)H_(5)-CO-COOH`
C. `C_(6)H_(5)-underset(OH)underset(|)CH-COOH`
D. `C_(6)H_(5)-underset(NH_(2))underset(|)CH-COOH`

Explanation

To determine which carboxylic acid undergoes decarboxylation easily, we need to analyze the options provided. The key concept here is that beta-keto carboxylic acids can undergo decarboxylation readily upon heating.

### Step-by-Step Solution:

1. **Identify the Structure of Carboxylic Acids**:
- Look at the given options and identify the structures of the carboxylic acids.
- Specifically, focus on the positioning of the carboxylic group (-COOH) relative to any carbonyl groups (C=O).

2. **Check for Beta-Keto Carboxylic Acids**:
- A beta-keto carboxylic acid has a carbonyl group (C=O) at the beta position (the second carbon) relative to the carboxylic acid group.
- This structure is crucial because it allows for the loss of carbon dioxide (CO2) when heated.

3. **Analyze the Heating Process**:
- When a beta-keto carboxylic acid is heated, it can undergo decarboxylation, which involves the removal of CO2.
- The reaction can be summarized as:
\[ \text{RCOCOOH} \xrightarrow{\text{heat}} \text{RCO} + \text{CO}_2 \]
- Here, R represents the rest of the molecule.

4. **Identify the Product**:
- After the decarboxylation, the product will be a ketone or an aldehyde depending on the structure of the starting carboxylic acid.
- For example, if the starting material is a beta-keto carboxylic acid, the product will be a ketone.

5. **Select the Correct Option**:
- From the options provided, identify which one is a beta-keto carboxylic acid.
- This compound will be the one that undergoes decarboxylation easily.

### Conclusion:
The carboxylic acid that undergoes decarboxylation easily is the beta-keto carboxylic acid.