The mechanism of SN1 reaction is given below :
`CH_(3)-underset(CH_(3)) underset(|) overset(CH_(3)) overset(|)C-Broverset("step-1")toCH_(3)-underset(CH_(3)) underset(|)overset(o+)C-CH_(3)+ Br^(-) overset(Nu)underset("step-II")to CH_(3)- underset(CH_(3)) underset(|)overset(CH_(3))overset(|)C-Nu`
Given answer of the following questions on the basis of the mechanism given below.
Which statement is NOT correct ?

Options

A. The reaction is first order reaction with respect to `Nu^-`
B. The reaction is first order with respect to alkyl halide
C. tert-butyl iodides is more reactive that tert-buty chloride
D. Optically active alkyl halide gives enantiomers

Answer

To determine which statement is NOT correct based on the given mechanism of the SN1 reaction, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding SN1 Mechanism**:
- The SN1 reaction involves two steps:
- **Step 1**: Formation of a carbocation from the alkyl halide (in this case, tertiary butyl bromide).
- **Step 2**: Nucleophilic attack on the carbocation to form the final product.

2. **Analyzing the Statements**:
- **Statement 1**: "The reaction is first order with respect to nucleophile."
- **Analysis**: In an SN1 reaction, the rate of reaction depends only on the concentration of the substrate (alkyl halide) and not on the nucleophile. Therefore, this statement is NOT correct.

- **Statement 2**: "The reaction is first order with respect to alkyl halide."
- **Analysis**: This statement is correct because the rate of an SN1 reaction is indeed first order with respect to the alkyl halide.

- **Statement 3**: "Tertiary butyl iodide is more reactive than tertiary butyl fluoride."
- **Analysis**: This statement is correct because iodide (I-) is a better leaving group than fluoride (F-), making tertiary butyl iodide more reactive than tertiary butyl fluoride.

- **Statement 4**: "Optically active alkyl halide gives enantiomers in SN1 reaction."
- **Analysis**: This statement is also correct. When an optically active compound forms a planar carbocation, the nucleophile can attack from either side, leading to the formation of two enantiomers.

3. **Conclusion**:
- The only statement that is NOT correct is **Statement 1**: "The reaction is first order with respect to nucleophile."

### Final Answer:
The statement that is NOT correct is: **"The reaction is first order with respect to nucleophile."**

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