WHY DO WE GET ISOPROPYL BENZENE ON TREATING BENZENE WITH 1-CHLOROPROPANE INSTEAD OF N-PROPYL BENZENE?

Dear Student

 

This is an example of electrophilic substitution reaction. The 1-chloropropane produces n-propyl cation which stabilises through reonance and produces 2-propyl cation. 

Since 1º-carbocations are prone to rearrangement, it is usually not possible to introduce 1º-alkyl substituents larger than ethyl by Friedel-Crafts alkylation. So, reaction of excess benzene with 1-chloropropane and aluminum chloride gives a good yield of isopropylbenzene (cumene).

 

C₆H₆ (large excess)  +  CH₃CH₂CH₂-Cl  +  AlCl₃   ——>   C₆H₅-CH(CH₃)₂  +  HCl

 

We hope that clarifies your query.

Regards

Team

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