Which of the following is the most reactive with HCl in the presence of `ZnCl_(2)`?

Options

A. `(CH_(3))_(3)COH`
B. `(CH_(3))_(2)CHCH_(2)OH`
C. `(CH_(3))_(2)CHOH`
D. `C_(6)H_(5)OH`

Answer

To determine which of the given compounds is the most reactive with HCl in the presence of ZnCl2, we need to analyze the stability of the carbocations formed during the reaction. The reaction mechanism involves the formation of carbocations, and the stability of these carbocations directly influences the reactivity of the alcohols with HCl.

### Step-by-Step Solution:

1. **Identify the Type of Alcohols**:
- We need to identify the types of alcohols provided in the options (primary, secondary, or tertiary).

2. **Understanding the Reaction**:
- The reaction of alcohols with HCl in the presence of ZnCl2 is known as the Lucas test. ZnCl2 acts as a catalyst and helps in the formation of a carbocation.

3. **Carbocation Formation**:
- When alcohol reacts with ZnCl2, the oxygen atom of the alcohol donates a lone pair to ZnCl2, leading to the formation of a carbocation. The stability of this carbocation is crucial for determining reactivity.

4. **Stability of Carbocations**:
- Carbocations are classified based on their stability:
- Tertiary (3°) carbocations are the most stable.
- Secondary (2°) carbocations are less stable than tertiary but more stable than primary (1°).
- Primary (1°) carbocations are the least stable.
- Therefore, the order of stability is: 3° > 2° > 1°.

5. **Analyzing Each Option**:
- **Option 1**: Tertiary alcohol (3°) → Forms a stable 3° carbocation.
- **Option 2**: Secondary alcohol (2°) → Forms a less stable 2° carbocation.
- **Option 3**: Primary alcohol (1°) → Forms the least stable 1° carbocation.
- **Option 4**: Phenol → Forms a benzyl carbocation, which is less stable due to sp² hybridization.

6. **Conclusion**:
- Among the options, the tertiary alcohol will form the most stable carbocation and thus will be the most reactive with HCl in the presence of ZnCl2.

### Final Answer:
The most reactive compound with HCl in the presence of ZnCl2 is the **tertiary alcohol** (Option 1).