Chemistry - GOC Question with Solution | TestHub

$\mathrm{I}$ is an allylic cation with oxygen donation at the far end: ${\mathrm{CH}}_3\mathrm{O}-\mathrm{CH}=\mathrm{CH}-{\mathrm{CH}}_2^{+}$ ↔ ${\mathrm{CH}}_3\mathrm{O}-\mathrm{CH}+$-$\mathrm{CH}={\mathrm{CH}}_2$ ↔ ${\mathrm{CH}}_3{\mathrm{O}}^{+}=\mathrm{CH}-\mathrm{CH}={\mathrm{CH}}_2$. This combines extended conjugation and an oxonium contributor with a complete octet. IV, ${\mathrm{CH}}_3\mathrm{O}-{\mathrm{CH}}_2^{+}$, also has direct oxygen donation and an octet oxonium contributor, but less extensive delocalization. $\mathrm{II}$ is allylic, yet $\mathrm{OMe}$ is attached to the central carbon and cannot give the same terminal oxonium stabilization. $\mathrm{III}$ lacks adjacent pi resonance or direct oxygen donation; oxygen chiefly withdraws inductively. Hence $\mathrm{I}$ > IV > $\mathrm{II}$ > $\mathrm{III}$. The third structure label is corrected to $\mathrm{III}$.