Arrange carbocation stability from least to most stable.

• A. Primary < Secondary < Tertiary
• B. Tertiary < Secondary < Primary
• C. Secondary < Primary < Tertiary
• D. Primary < Tertiary < Secondary

Answer: (A)

Carbocation stability depends on how many alkyl groups can donate electron density to the positively charged carbon. Each alkyl group provides hyperconjugation and inductive effects that help spread out the charge. A primary carbocation has only one alkyl substituent, so it receives the least stabilization. A secondary carbocation has two alkyl groups and is more stabilized. A tertiary carbocation, with three alkyl groups, gets the most stabilization. Therefore, the order from least to most stable is primary, then secondary, then tertiary.