3,3-dimethyl-1-butene is reacted with concentrated . The isolated major product differs structurally — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

The addition of $H^+$ to 3,3-dimethyl-1-butene ($CH_2=CH-C(CH_3)_3$) yields the more stable $2^\circ$ carbocation: $CH_3-C^+H-C(CH_3)_3$. However, this $2^\circ$ cation is immediately adjacent to a quaternary carbon possessing three methyl groups. To achieve greater thermodynamic stability, a methyl group migrates with its bonding electrons (a 1,2-methanide shift) to the adjacent positive carbon. This rearrangement yields a highly stable $3^\circ$ carbocation: $CH_3-CH(CH_3)-C^+(CH_3)_2$. The chloride nucleophile then traps this cation, producing the major rearranged product: 2-chloro-2,3-dimethylbutane.