Question

Which is the stable form of the given carbocation after rearrangement?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Carbocation (a) is formed by 1, 2 H-shift to give primary carbocation which is less stable than secondary carbocation. Hence, it is not formed.
Carbocation (b) is formed by ring expansion from six membered ring to seven membered but six membered ring is stable than seven membered so it is not formed.
Carbocation (d) is formed by 1, 2 H-shift to give tertiary carbocation which is more stable than secondary.
The positive charge on six membered ring is stable so it won't undergo ring contraction to give carbocation (c).
Hence, carbocation (d) is more stable form.