Question

When benzene treated with n- propyl chloride main product is iso-propyl benzene give mechanism

Answer 1

Can we prepare cumene using benzene and n-propyl chloride in presence of FeCl3?

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Chetan Pandey, Studied chemistry at High school

Updated Dec 27, 2015 · Author has 333 answers and 315.2k answer views

Yeah we can, although theoretically.

The structure of n-propyl chloride is as follows



In a standard reaction of Electrophilic Aromatic Substitution, or more precisely the Friedel-Crafts Alkylation, a haloalkane first reacts with a metal chloride like FeCl3FeCl3 to form the corresponding carbocation of the alkane, which then attacks the benzene ring to undergo electrophilic substitution.

When n-propyl chloride reacts with FeCl3FeCl3, it forms FeCl−4FeCl4−and n-propyl carbocation. This carbocation undergoes rearrangement to form isopropyl carbocation.

This isopropyl carbocation will then attack the benzene ring to form Cumene, in an EAS.

The formula for the complete reaction reaction will be:

CH3CH2CH2Cl+C6H6−→−−FeCl3C6H5CH(CH3)2+HClCH3CH2CH2Cl+C6H6→FeCl3C6H5CH(CH3)2+HCl



Mechanism:

1) CH3CH2CH2Cl+FeCl3→CH3CH2CH+2+FeCl−4CH3CH2CH2Cl+FeCl3→CH3CH2CH2++FeCl4−

2) CH3CH2CH+2→(CH3)2CH+CH3CH2CH2+→(CH3)2CH+

3) (CH3)2CH++C6H6→C6H5CH(CH3)2+H+(CH3)2CH++C6H6→C6H5CH(CH3)2+H+

4) H++FeCl−4→FeCl3+HClH++FeCl4−→FeCl3+HCl

Thanks :)

Special Thanks to Nissim Raj Angdembay who suggested some invaluable edits. :)

EDIT 1