Question

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

• A.
• B.
• C.
• D.

Answer 1

The correct option is D


$-N{O}_2$ group shows electron-withdrawing $(-R)$ effect. The carbocations directly attached to the nitro group are highly unstable. As we can see in option (c) and (d) are highly unstable.
In option b also after resonance the carbocation formed is directly attached to the nitro so, it is also unstable.

Option a 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 (a).