Compound (A) `C_(8)H_(9)Br`. Gives a white precipitate when warmed with alcoholic `AgNO_(3)`. Oxidation of (A) gives an acid (B). `C_(8)H_(6)O_(4)`. (B) easily forms anhydride on heating. Identify the compound (A)

Options

A.
B.
C.
D.

Answer

To identify compound (A) with the molecular formula \( C_8H_9Br \), we need to analyze the information given in the question step by step.

### Step 1: Analyze the Reaction with Alcoholic AgNO3
The compound (A) gives a white precipitate when warmed with alcoholic \( AgNO_3 \). This indicates that (A) contains a bromine atom that can be replaced by the alkoxy group from the alcohol in the reaction. The precipitate formed is \( AgBr \), which is typically light yellow.

### Step 2: Determine the Structure of Compound (A)
Given the molecular formula \( C_8H_9Br \), we can deduce that (A) likely contains a bromine atom attached to a carbon chain or a ring structure. The presence of 9 hydrogens suggests that there may be a double bond or a ring structure, as each bromine substitution reduces the number of hydrogens.

### Step 3: Oxidation of Compound (A)
The oxidation of (A) produces an acid (B) with the formula \( C_8H_6O_4 \). This indicates that upon oxidation, two hydrogen atoms are replaced with carboxylic acid groups (\(-COOH\)).

### Step 4: Identify the Structure of Acid (B)
The molecular formula \( C_8H_6O_4 \) suggests that (B) has two carboxylic acid groups. Since it can easily form an anhydride upon heating, it is likely that (B) is phthalic acid, which has the structure:

\[ \text{C}_6\text{H}_4(\text{COOH})_2 \]

### Step 5: Identify Compound (A) Based on the Structure of (B)
To form phthalic acid from (A), (A) must be a bromo derivative of a compound that can oxidize to form two carboxylic acid groups. The most likely candidate is 1-bromo-2-methylbenzene (o-bromotoluene), which has the structure:

\[ \text{C}_6\text{H}_4(\text{Br})(\text{CH}_3) \]

### Step 6: Confirm the Structure of (A)
1. **Reactivity with \( AgNO_3 \)**: The bromo group in 1-bromo-2-methylbenzene will react with alcoholic \( AgNO_3 \) to form \( AgBr \).
2. **Oxidation**: Upon oxidation, the methyl group can be converted to a carboxylic acid, yielding phthalic acid.
3. **Formation of Anhydride**: Phthalic acid can easily lose water to form phthalic anhydride upon heating.

### Conclusion
Thus, the compound (A) is identified as **1-bromo-2-methylbenzene**.