Question

The decreasing order of the stability of the ions

• A. I > II > III
• B. III > II > I
• C. II > III > I
• D. II > I > III

Answer 1

Answer: (D)

$C{H}_3-\stackrel{+}{C}H-OC{H}_3$ is most stable due to resonance

Carbocation $C{H}_3-\stackrel{+}{C}H-COC{H}_3$ is least stable due to electron withdrawing nature of carbonyl group. Carbocation $C{H}_3-\stackrel{+}{C}H-C{H}_3$ is less stable than
$C{H}_3-\stackrel{+}{C}H-OC{H}_3$ because it stabilised only by the $+I$ effect of the two methyl groups.

Therefore, correct order of decreasing stability is $II>I>III$