Which of the following will react most readily with HI ?

Options

A. `CH_(3)OH`
B. `(CH_(3))_(3)COH`
C. `CH_(3)CH_(2)OH`
D. `(CH_(3))_(2)CHOH`

Answer

To determine which compound reacts most readily with HI, we need to analyze the structures of the given options and understand the mechanism of the reaction.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Option A: CH₃OH (Methanol)
- Option B: CH₃CHOHCH₃ (Isopropanol)
- Option C: CH₃CH₂OH (Ethanol)
- Option D: (CH₃)₂CHOH (Tertiary alcohol)

2. **Understand the Reaction Mechanism**:
- HI dissociates into H⁺ and I⁻. The H⁺ will protonate the hydroxyl group (OH) in the alcohol, forming a positively charged oxonium ion (R-OH₂⁺).
- This oxonium ion can then lose water (H₂O), forming a carbocation (R⁺).

3. **Carbocation Stability**:
- The stability of the carbocation formed is crucial for the reaction rate. The order of carbocation stability is:
- Tertiary (3°) > Secondary (2°) > Primary (1°) > Methyl (0°).

4. **Analyze Each Option**:
- **Option A (CH₃OH)**: Forms a primary carbocation (least stable).
- **Option B (CH₃CHOHCH₃)**: Forms a secondary carbocation (more stable than primary).
- **Option C (CH₃CH₂OH)**: Forms a primary carbocation (least stable).
- **Option D ((CH₃)₂CHOH)**: Forms a tertiary carbocation (most stable).

5. **Determine the Most Readily Reacting Compound**:
- Since the tertiary carbocation is the most stable, the compound that will react most readily with HI is **Option D: (CH₃)₂CHOH**.

### Conclusion:
Thus, the compound that reacts most readily with HI is **(CH₃)₂CHOH (Tertiary alcohol)**.

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