Question

Statement-1 : Benzyl chloride reacts faster than ethyl chloride towards $S_N1$.
Statement-2 : Positive charge on ethyl will be unstable.

• (1) Statement-I and statement-II both are correct.
• (2) Statement-I and statement-II both are incorrect.
• (3) Statement-I correct but statement-II is incorrect.
• (4) Statement-I incorrect but statement-II is correct.

Answer 1

The Correct Option is A

The rate of $S_N1$ reactions depends on the stability of the carbocation intermediate formed during the rate-determining step.
1. Evaluate Statement-1:
In $S_N1$, Benzyl chloride forms the benzyl carbocation ($Ph-CH_2^+$). Ethyl chloride forms the ethyl carbocation ($CH_3-CH_2^+$). The benzyl carbocation is highly stabilized by resonance with the benzene ring. The ethyl carbocation is only weakly stabilized by hyperconjugation and +I effect. Thus, benzyl chloride reacts much faster. Statement-1 is correct.

2. Evaluate Statement-2:
The ethyl carbocation is a primary carbocation. Compared to the resonance-stabilized benzyl carbocation, it is significantly less stable (unstable in a relative sense). Since its instability explains why its precursor reacts slower than benzyl chloride, this acts as a reason. Statement-2 is correct.

Conclusion: Both statements are correct, and Statement-2 explains Statement-1. Option (1).