Which among the following is not true for the hydrolysis of t - butyl bromide with aqueous NaOH ?

Options

A. Reaction occurs through the `S_N1` mechanism.
B. The intermediate formed is a carbocation.
C. Rate of the reaction doubles when concentration of alkali is doubled.
D. Rate of the reaction doubles when the concentration of t - butyl bromide is doubled.

Answer

To solve the question, we need to analyze the hydrolysis of t-butyl bromide with aqueous NaOH and determine which statement is not true regarding this reaction.

### Step-by-Step Solution:

1. **Understanding the Reaction Mechanism**:
- The hydrolysis of t-butyl bromide (tert-butyl bromide) occurs through an SN1 mechanism. In this mechanism, the reaction proceeds in two steps:
- First, the leaving group (Br) departs, forming a carbocation.
- Second, the nucleophile (OH⁻ from NaOH) attacks the carbocation.

**Hint**: Recall that SN1 reactions are characterized by the formation of a carbocation intermediate.

2. **Carbocation Formation**:
- The structure of t-butyl bromide is (CH₃)₃CBr. When Br leaves, it forms a tertiary carbocation, which is stable due to hyperconjugation and inductive effects from the surrounding alkyl groups.

**Hint**: Remember that tertiary carbocations are more stable than secondary or primary carbocations.

3. **Rate of Reaction**:
- In an SN1 reaction, the rate of reaction depends only on the concentration of the substrate (alkyl halide) and not on the concentration of the nucleophile. Therefore, doubling the concentration of NaOH (the nucleophile) does not affect the rate of reaction.

**Hint**: Focus on the fact that in SN1 reactions, the rate is determined by the formation of the carbocation, which depends solely on the substrate.

4. **Evaluating the Statements**:
- **Option 1**: The reaction occurs through an SN1 mechanism. (True)
- **Option 2**: The intermediate formed is a carbocation. (True)
- **Option 3**: The rate of reaction doubles when the concentration of alkali is doubled. (Not true)
- **Option 4**: The rate of reaction doubles when the concentration of t-butyl bromide is doubled. (True)

**Hint**: Compare each statement against the principles of SN1 reactions to identify the false statement.

5. **Conclusion**:
- The statement that is not true is option 3: "The rate of reaction doubles when the concentration of alkali is doubled." This is incorrect because the rate of an SN1 reaction does not depend on the concentration of the nucleophile.

### Final Answer:
The statement that is not true for the hydrolysis of t-butyl bromide with aqueous NaOH is option 3.