Question

Which of the following carbocations is expected to be most stable?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

$-N{O}_2$​ group shows electron-withdrawing (-I) effect and is a meta directing group. The carbocations directly attached to the nitro group are highly unstable. Hence, option (a) and (c) are highly unstable. In option (b) also, after resonance the carbocation formed is directly attached to the nitro and thus it is also unstable.
Option (d) the carbocation is at para position w.r.t nitro group and even after resonance the carbocation forms at ortho position only. Thus the most stable carbocations is shown in option (d).