Question

Arrange following carbocation in the decreasing order of stability
(i) $C\text{H}_{3}-\overset{+}{C}H-CH_{3}$
(ii) $CH_{3}-\overset{+}{C}H-O-CH_{3}$
(iii) $CH_{3}-\overset{+}{C}H-CO-CH_{3}$

• A. $\left(\right.iii\left.\right)>\left(\right.ii\left.\right)>\left(\right.i\left.\right)$
• B. $\left(\right.i\left.\right)>\left(\right.ii\left.\right)>\left(\right.iii\left.\right)$
• C. $\left(\right.ii\left.\right)>\left(\right.i\left.\right)>\left(\right.iii\left.\right)$
• D. $\left(\right.i\left.\right) < \left(\right.ii\left.\right) < \left(\right.iii\left.\right)$

Answer 1

Answer: (C)

Carbocation are stabilised by back bonding and electron donating groups (EDG) while destabilised by electrons withdrawing groups (EWG).
$CH_{3}-\overset{+}{C}H-O-CH_{3}$ (back bonding) > $\text{C}\text{H}_{3}-\overset{+}{C}H-CH_{3}$ (EDG) > $CH_{3}-\overset{+}{C}H-CO-CH_{3}$ (EWG)