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 will react most readily with HI, we need to analyze the stability of the carbocation intermediates formed during the reaction. The reaction mechanism involved is SN1, which proceeds through the formation of a carbocation.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- HI (hydroiodic acid) can react with alcohols. The reaction involves the protonation of the alcohol, leading to the formation of a carbocation.

2. **Protonation of Alcohol**:
- The alcohol (ROH) is protonated by HI to form ROH2⁺. This step is crucial as it prepares the alcohol for the loss of water (a leaving group).

3. **Formation of Carbocation**:
- The protonated alcohol (ROH2⁺) can lose a water molecule (H2O) to form a carbocation (R⁺). The stability of this carbocation is key to determining the reactivity with HI.

4. **Stability of Carbocations**:
- Carbocation stability increases with the number of alkyl groups attached to the positively charged carbon. The order of stability is:
- Tertiary (3°) > Secondary (2°) > Primary (1°) > Methyl (0°)
- This is due to the +I (inductive) effect of alkyl groups, which donate electron density to the positively charged carbon.

5. **Comparing the Given Options**:
- For each option provided, we need to determine the type of carbocation that would form upon reaction with HI.
- Identify whether the carbocation formed is primary, secondary, or tertiary.

6. **Conclusion**:
- The compound that forms the most stable (tertiary) carbocation will react most readily with HI. Therefore, the answer is the compound that leads to a tertiary carbocation upon reaction.

### Final Answer:
The compound that will react most readily with HI is the one that forms the most stable carbocation, which is typically a tertiary carbocation.

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