Question

Statement I: High concentration of strong nucleophilic reagent with secondary alkyl halides which do not have bulky substituents will follow $S_N2$ mechanism.

Statement II: A secondary alkyl halide when treated with a large excess of ethanol follows $S_N1$ mechanism.

In the light of the above statements, choose the most appropriate from the questions given below:

• A. Both statements are true
• B. Statement I is true, II is false
• C. Both statements are false
• D. Statement I is false, Statement II is true

Answer 1

Answer: (A)

Both statements are true

Answer 2

Analysis of Statement I: SN2 reactions are characterized by a single concerted step where the nucleophile attacks the substrate from the opposite side of the leaving group. High concentration of a strong nucleophile enhances the rate of SN2 reactions, especially with secondary alkyl halides that are not hindered by bulky substituents. Thus, Statement I is true.

Analysis of Statement II: SN1 reactions occur in two steps: formation of a carbocation intermediate followed by nucleophilic attack. Secondary alkyl halides can undergo SN1 reactions in the presence of polar protic solvents like ethanol. A large excess of ethanol serves as a nucleophile and stabilizes the carbocation, favoring the SN1 mechanism. Thus, Statement II is also true.

Therefore, both statements are correct: Both Statement I and Statement II are true.