Which of the following statement is false regarding `S_N2` reaction shown by alkyl halides ?

Options

A. The conversion of reactants to transition state is the rate determining step
B. The `S_N2` reaction involves the stereochemistry around carbon atoms of the substrate.
C. The rate of reaction depends on the stric bulk of the alkyl group
D. The nucleophilicity of halides follows the order `Cl^(-) gt Br^(-) gt I^(-).`

Explanation

To determine which statement is false regarding the \( S_N2 \) reaction shown by alkyl halides, we will analyze each option based on the characteristics of the \( S_N2 \) mechanism.

### Step-by-Step Solution:

1. **Understanding the \( S_N2 \) Mechanism**:
- The \( S_N2 \) reaction stands for bimolecular nucleophilic substitution. In this mechanism, a nucleophile attacks the electrophilic carbon atom from the opposite side of the leaving group (halide), leading to a transition state where both the nucleophile and the leaving group are partially bonded to the carbon.

2. **Analyzing Each Option**:
- **Option A**: "Conversion of reactant to transition state is the rate determining step."
- This statement is true. The formation of the transition state is indeed the rate-determining step (RDS) in an \( S_N2 \) reaction.

- **Option B**: "The \( S_N2 \) reaction involves the stereochemistry around the carbon atoms of the substrate."
- This statement is also true. The \( S_N2 \) reaction results in inversion of configuration at the carbon atom, meaning the stereochemistry is affected.

- **Option C**: "The rate of reaction depends on the steric bulk of the alkyl group."
- This statement is true as well. In \( S_N2 \) reactions, increased steric hindrance from bulky groups slows down the reaction rate because it makes it harder for the nucleophile to approach the electrophilic carbon.

- **Option D**: "Nucleophilicity of halides follows the order of chlorine, bromine, and iodine."
- This statement is false. The correct order of nucleophilicity for halides in \( S_N2 \) reactions is \( I^- > Br^- > Cl^- \). Iodide is the best nucleophile due to its larger size and lower electronegativity compared to bromine and chlorine.

3. **Conclusion**:
- The false statement regarding \( S_N2 \) reactions shown by alkyl halides is **Option D**.

### Final Answer:
**The false statement is Option D: "Nucleophilicity of halides follows the order of chlorine, bromine, and iodine."**

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