Question

Increasing rate of $S_{N}1$ reaction in the following compounds is:

• A. $\left(B\right)<\left(A\right)<\left(C\right)<\left(D\right)$
• B. $\left(B\right)<\left(A\right)<\left(D\right)<\left(C\right)$
• C. $\left(A\right)<\left(B\right)<\left(D\right)<\left(C\right)$
• D. $\left(A\right)<\left(B\right)<\left(C\right)<\left(D\right)$

Answer 1

The correct option is A $\left(B\right)<\left(A\right)<\left(C\right)<\left(D\right)$

Rate of $S_{N}1$ is directly proportional to the stability of carbocation formed in the intermediate step.
Electron donating species will stabilise the carbocation formed enhancing the rate whereas electron withdrawing group will destabilise the carbocation and thus will decrease the rate. In B ,inductive effect predominates over +R effect since it is at the meta position.