`C_(6) H_(5)NH_(2) underset (0-5^(@))overset(HNO_(2)//HCI)to X underset(H_(2)O)overset(Delta)to ` Phenol, Here X is :

Options

A. `C_(6) H_(5)NH_(2)- overset(o+)(N_(2))overset(Theta)(CI)`
B. `C_(6) H_(5)NH_(2)- N =C`
C. `C_(6) H_(5)NH_(2)- NH(CH_(3))`
D. `C_(6) H_(5)NH_(2) - CN`

Answer

To solve the question, we need to determine the compound X that results from the reaction of aniline (C₆H₅NH₂) with nitrous acid (HNO₂) in the presence of hydrochloric acid (HCl) at low temperatures (0-5°C), and then subsequently reacts with water upon heating to form phenol.

### Step-by-Step Solution:

1. **Identify the Reactant**:
The reactant is aniline, which has the chemical formula C₆H₅NH₂. It consists of a benzene ring (C₆H₅) attached to an amino group (NH₂).

2. **Reaction with HNO₂ and HCl**:
When aniline reacts with nitrous acid (HNO₂) in the presence of hydrochloric acid (HCl) at low temperatures (0-5°C), it undergoes a process known as diazotization. This reaction converts the amino group (-NH₂) into a diazonium group (-N₂⁺).

The reaction can be summarized as follows:
\[ C₆H₅NH₂ + HNO₂ + HCl \rightarrow C₆H₅N₂Cl + 2H₂O \]
Here, X is benzene diazonium chloride, which has the formula C₆H₅N₂⁺Cl⁻.

3. **Formation of Phenol**:
The next step involves heating the benzene diazonium chloride (X) in the presence of water. Upon heating, the diazonium group (N₂) is released as nitrogen gas (N₂), and a carbocation is formed.

The reaction can be represented as:
\[ C₆H₅N₂Cl + H₂O \xrightarrow{\Delta} C₆H₅OH + HCl + N₂ \]
Here, the water molecule attacks the carbocation, leading to the formation of phenol (C₆H₅OH).

4. **Conclusion**:
Therefore, the compound X formed during the diazotization of aniline is benzene diazonium chloride, which can be represented as C₆H₅N₂⁺Cl⁻.

### Final Answer:
X is C₆H₅N₂⁺Cl⁻ (benzene diazonium chloride).

---