In an attempt to prepare n−propylbenzene, a chemist alkylated benzene with 1−chloropropane and aluminum chloride. however, two isomeric hydrocarbons were obtained in a ratio of 2: 1, the desired n−propylbenzene being the minor component. what do you think was the major product? how did it arise?

2-Phenylpropane (Cumene)

Explanation:

Famous Friedel Craft Alkylation.

Aluminum Chloride grasped the 1-chloropropane forming an intermediate product composed of Aluminum tetrachloride and n-propylcation. It is well understood that primary carbocations are unstable and therefore undergo hydrogen shifting to attain stability. n-Propylcarbocation undergone hydrogen shifting, forming isopropylcarbocation which reacted with benzene forming 2-Phenylpropane as the major product and HCl as a byproduct.

AlCl3 + CH3CH2CH2Cl --> AlCl4-   +   CH3CH2CH2+

CH3CH2CH2+  ---> CH3CH(+)CH3

C6H6 + CH3CH(+)CH3 ---> C6H5CH(CH3)2   + H+

AlCl4- + H+ ---> HCl + AlCl3

From the given problem statement,he was attempting to prepare n−propylbenzene by alkylation benzene with 1−chloropropane and aluminum chloride,but 1-propyle benze was a major product in result.