JEE Main · 2024 · 30 Jan 2024 · Shift 2 · General Organic Chemistry

Carbocation stability rises with the number of alkyl groups on the positively charged carbon, since each adjacent C–H bond can hyperconjugate into the empty p-orbital and each alkyl group's +I effect helps disperse the positive charge. The tertiary cation $({\text{CH}}_3{)}_3\stackrel{+}{C}$ has nine hyperconjugating hydrogens and is most stable; the secondary $({\text{CH}}_3{)}_2\stackrel{+}{C}\text{H}$ has six; the primary ${\text{CH}}_3\text{–}\stackrel{+}{C}{\text{H}}_2$ has three; the methyl cation $\stackrel{+}{C}{\text{H}}_3$ has none and is least stable. The order of stability is $({\text{CH}}_3{)}_3\stackrel{+}{C}>({\text{CH}}_3{)}_2\stackrel{+}{C}\text{H}>{\text{CH}}_3\text{–}\stackrel{+}{C}{\text{H}}_2>\stackrel{+}{C}{\text{H}}_3$.