Question

Heating many alkyl chlorides or bromides in water effects their conversion into alcohol through a $S_{N}1$ reaction. Order of the above sets compounds with respect to solvolytic reactivity is :

• A. II > I>III
  
• B. III < II < I
• C. III > II > I
• D. None

Answer 1

The correct option is C III > II > I

In $S_{N}1$, mechanism RDS step is the formation of the carbocation.

So, the rate of reaction is directly proportional to the stability of carbocation forms.

$Rateofreaction\propto stabilityofcarbocation\left(C^{+}\right)$

order of stability of $C^{+}$ is ($3^0>2^0>1^0$)

Thus, option C is correct.