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Why do we get isoproyl benzene on treating benzene with 1-chloropropane instead of n-propyl benzene?

Is it because of Markovnikov's rule?

Karthik
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2 Answers2

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First AlCl3 converts 1-chloropropane into propane with a positive charge on terminal carbon

Since secondary carbocation is more stable than primary carbocation it undergoes rearrangement and positive charge shifts to secondary carbonation atom.

Hence we get isopropyl benzene

ULTIMATEGAMER07
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  • Markovnikov's rule is just the beginning..It's better to understand the mechanism of how carbocations rearrange themselves to form stable compounds. Then markovnikov's rule will become obvious. – ULTIMATEGAMER07 Mar 04 '17 at 04:53
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The Lewis acid will pull off the chlorine creating a primary carbocation, primary carbocations are very unstable and are almost always unfavorable. The propane will preform a hydride shift bringing the carbocation to the 2' carbon creating a secondary carbocation. Side note because this is an intermolecular reaction it takes place significantly faster than the actual alkylation. Then the Pi electrons from one of the double bonds in the benzene will attack the carbocation and you clearly know the rest.

Gunnar
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