`C_8H_6O_4 overset Delta rarr X overset (NH_3) rarr Y`
The compound Xis

Options

A. o- xylene
B. phthalic acid
C. phthalic anhydride
D. salicylic acid

Answer

To solve the problem step by step, we will analyze the given compound \( C_8H_6O_4 \) and determine what compound \( X \) is after heating, and then what compound \( Y \) is after reacting \( X \) with \( NH_3 \).

### Step 1: Identify the structure of \( C_8H_6O_4 \)

1. **Calculate the Double Bond Equivalent (DBE)**:
- The formula for DBE is given by:
\[ \text{DBE} = N + 1 - \frac{A}{2} \]
- Where \( N \) is the number of carbon atoms and \( A \) is the number of hydrogen atoms plus halogens.
- For \( C_8H_6O_4 \):
- \( N = 8 \)
- \( A = 6 \) (only hydrogen is counted here, as there are no halogens)
- Plugging in the values:
\[ \text{DBE} = 8 + 1 - \frac{6}{2} = 9 - 3 = 6 \]

2. **Interpret the DBE**:
- A DBE of 6 suggests that the compound has multiple rings or double bonds. This indicates the presence of a benzene ring and several functional groups.

### Step 2: Determine the structure of \( X \)

1. **Recognize the compound**:
- The compound \( C_8H_6O_4 \) is known as **phthalic acid** (1,2-benzenedicarboxylic acid).
- When heated, phthalic acid undergoes dehydration, losing a water molecule.

2. **Write the dehydration reaction**:
- The dehydration of phthalic acid results in the formation of **phthalic anhydride**:
\[ \text{C}_8\text{H}_6\text{O}_4 \xrightarrow{\Delta} \text{C}_8\text{O}_3 \]
- Here, \( X \) is **phthalic anhydride**.

### Step 3: React \( X \) with \( NH_3 \)

1. **Reaction with ammonia**:
- When phthalic anhydride reacts with ammonia, it forms **phthalamic acid**:
\[ \text{C}_8\text{O}_3 + \text{NH}_3 \rightarrow \text{C}_8\text{H}_7\text{NO}_2 \]
- This compound \( Y \) is known as **phthalamic acid**.

### Conclusion

- Therefore, the compound \( X \) is **phthalic anhydride**.