Question

For the following carbocations, choose the correct option considering only inductive effect.

• A. (a) is more stable than (b).
• B. (a) is less stable than (b).
• C. Both are equally stable.
• D. Stability cannot be predicted.

Answer 1

The correct option is B (a) is less stable than (b).

Both Fluorine and Chlorine when attached to carbon act as electron withdrawing groups because of their higher electronegativity than carbon.
When an electron withdrawing group is attached to carbocation, it will reduce the stability because, the positive charge on carbocation will increase more due to electron withdrawing nature or $-I$ effect of the group
Since Fluorine is more electronegative than chlorine it will show higher $-I$ effect. Hence (a) will be less stable than (b)