Question

Which of the following halides will undergo S\(_2\) reaction?

(A) Chlorobenzene
(B) Benzyl chloride
(C) Tertiary-butyl chloride
(D) n-butyl chloride
Choose the correct answer from the options given below:

• A. (B) and (D) only.
• B. (B), (C) and (D) only.
• C. (A), (B) and (D) only.
• D. (A), (C) and (D) only.

Hint:

S\(_2\) reactions are favored by primary halides, benzyl halides, and allyl halides due to less steric hindrance.

Answer 1

The Correct Option is A

Step 1: Mechanism of S\(_2\) reaction.
The S\(_2\) reaction (bimolecular nucleophilic substitution) requires a backside attack on the electrophilic carbon. It typically occurs with primary or secondary alkyl halides, as well as with benzyl and allyl halides.
Step 2: Analyze each halide.
- Chlorobenzene (A): The carbon attached to the halogen is sp\(^2\) hybridized, making it very resistant to nucleophilic attack. It does not undergo an S\(_2\) reaction.
- Benzyl chloride (B): The benzyl group stabilizes the transition state, making this halide very reactive in an S\(_2\) reaction.
- Tertiary-butyl chloride (C): Due to the steric hindrance around the tertiary carbon, this halide does not undergo S\(_2\) reactions but follows an S\(_N\)1 mechanism.
- n-butyl chloride (D): This is a primary halide and undergoes S\(_2\) reactions very efficiently.
Step 3: Conclusion.
Thus, the halides that undergo S\(_2\) reactions are Benzyl chloride (B) and n-butyl chloride (D).
Final Answer: \[ \boxed{\text{(B) and (D) only}} \]