For the following Friedel-Craft's alkylation reaction, which of the statements are correct ?
A. Major product is n-propyl benzene.
B. iso-propyl carbocation intermediate is also generated.
C. Multiple substitution is inevitable.
D. Introducing electron-donating substituent on benzene will not produce any alkylbenzene.
Choose the correct answer from the options given below :
- A
A and D only
- B
B and C only
- C
A and C only
- D
B and D only
n-Propyl chloride with AlCl initially gives an n-propyl cation, which rapidly rearranges by a 1,2-hydride shift to the more stable isopropyl cation. The major product is therefore isopropylbenzene (cumene), not n-propylbenzene. So statement A is wrong and B is correct.
The first alkyl group introduced is electron-donating, activating the ring toward further alkylation. Polyalkylation is hard to avoid, so C is correct.
D is wrong: electron-donating substituents activate the ring and actually promote alkylation, giving products readily.
Correct: B and C.
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