Question

Which of the following chlorides is highly reactive in $S_{N}1$ reaction, even solvolysed in cold water?

• A.
• B.
• C.
• D. None of the above

Answer 1

The correct option is A

Chlorocycloheptane is more reactive in $S_{N}1$ reaction.
Rate of $S_{N}1$ reaction depends on the stability of the carbocation intermediate formed.
The tropylium ion formed from (a) is highly stable because is aromatic in nature. Hence, it is highly reactive even in cold water.

Aryl halide does not give stable carbocation and the cyclopentadienyl cation formed is antiaromatic which is also unstable.