A compound X has molecular formula `C_7H_7NO`. On treatment with `Br_2` and KOH, X gives an amine Y. The latter gives carbylamine test. Y upon diazotisation and coupling with phenol gives an azo dye. Thus, X is

Options

A. `C_6H_5NO_2`
B. `C_6H_5COONH_4`
C. `C_6H_5CONH_2`
D. None of these

Explanation

To solve the problem, we need to identify the compound X with the molecular formula C₇H₇NO, which on treatment with Br₂ and KOH gives an amine Y that passes the carbylamine test and can be diazotized and coupled with phenol to form an azo dye.

### Step-by-Step Solution:

1. **Identify the Molecular Formula**:
The molecular formula of compound X is given as C₇H₇NO. This indicates that it contains 7 carbon atoms, 7 hydrogen atoms, 1 nitrogen atom, and 1 oxygen atom.

2. **Consider Possible Structures for X**:
We need to consider possible structures that fit the molecular formula. One likely candidate is an amide, which can be represented as C₆H₅C(O)NH₂ (where C₆H₅ is a phenyl group).

3. **Reaction with Br₂ and KOH**:
The reaction of an amide with Br₂ and KOH typically leads to the formation of a primary amine through the Hofmann degradation reaction. In this case, the amide C₆H₅C(O)NH₂ would yield aniline (C₆H₅NH₂) as the amine Y.

4. **Carbylamine Test**:
Aniline (Y) is a primary amine and will give a positive carbylamine test. This test involves heating the amine with chloroform and alcoholic KOH, resulting in the formation of an isocyanide.

5. **Diazotization of Y**:
Aniline can be diazotized by treating it with nitrous acid (generated in situ from sodium nitrite and hydrochloric acid), forming a diazonium salt (C₆H₅N₂⁺Cl⁻).

6. **Coupling with Phenol**:
The diazonium salt can then couple with phenol to form an azo dye. The reaction involves the electrophilic substitution of the phenol by the diazonium ion, resulting in the formation of an azo compound (C₆H₅N=N-C₆H₅).

7. **Conclusion**:
Based on the above steps, we conclude that the compound X is C₆H₅C(O)NH₂, which is an amide. Upon treatment with Br₂ and KOH, it gives aniline, which meets all the criteria mentioned in the question.

### Final Answer:
Thus, the compound X is **C₆H₅C(O)NH₂** (an amide).

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