Identify the correct order of relative stability for the following carbocations: (I) (II) (III)

Step-by-step solution

Carbocation (I) is a vinylic carbocation ( CH₂=C^+-CH₃ ). The positive charge is present on an sp -hybridized carbon atom. Since sp -hybridized carbons are more electronegative, they do not readily accommodate a positive charge, making this carbocation highly unstable. Carbocation (II) is a secondary alkyl carbocation (isopropyl cation, CH₃-CH^+-CH₃ ). It is stabilized by hyperconjugation from six -hydrogens and the +I effect of two methyl groups. Carbocation (III) is a secondary benzylic carbocation (1-phenylethyl