When 1-chloropropane (n-propyl chloride) reacts with benzene in the presence of , a carbocation rear — Aromatic Hydrocarbons Chemistry Question
Question
When 1-chloropropane (n-propyl chloride) reacts with benzene in the presence of $AlCl_3$, a carbocation rearrangement takes place. What is the difference in the number of hyperconjugative alpha-hydrogens between the initial primary carbocation formed and the rearranged secondary carbocation?
💡 Solution & Explanation
The initial primary carbocation is $CH_3-CH_2-CH_2^+$, which has 2 alpha-hydrogens on the adjacent methylene group. After a 1,2-hydride shift, the isopropyl cation, $CH_3-CH^+-CH_3$, is formed. The isopropyl cation is stabilized by 6 alpha-hydrogens from the two methyl groups. The difference is $6 - 2 = 4$.