Assume the secondary cation $(cyclobutyl) - CH X^{+} - CH X_{3}$ from protonation of vinylcyclobutane rearranges, by ring expansion and then a hydride shift, until the cation is tertiary. It is then captured by $Cl X^{-}$ . The final product is

A1-chloro-1-methylcyclopentane
B1-chloro-2-methylcyclopentane
C(1-chloroethyl)cyclobutane
D1-chloro-1-ethylcyclobutane

Answer: A

A ring carbon migrates to the cationic carbon, expanding the four-membered ring to five and relieving strain. The new cation is secondary and adjacent to the carbon bearing

CH X_{3}

. A hydride shift from that carbon gives the tertiary 1-methylcyclopentyl cation, which gives 1-chloro-1-methylcyclopentane.

Practice Organic Reaction Mechanisms II: Electrophilic and Radical Reactions More on Carbocation rearrangements in addition

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Assume the secondary cation (cyclobutyl)−CHX+−CHX3​ from protonation of vinylcyclobutane rearranges, by ring expansion and then a hydride shift, until the cation is tertiary. It is then captured by ClX−. The final product is

Answer: A

More questions on Carbocation rearrangements in addition

Assume the secondary cation $(cyclobutyl) - CH X^{+} - CH X_{3}$ from protonation of vinylcyclobutane rearranges, by ring expansion and then a hydride shift, until the cation is tertiary. It is then captured by $Cl X^{-}$ . The final product is