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

Asked by kuldeep shrivastava | 21st Feb, 2011, 12:27: PM

Expert Answer:

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.
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Answered by  | 21st Feb, 2011, 07:54: PM

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