SUBSTITUENT EFFECTS ON THE REACTIVITY OF BENZENE RINGS

Predict the structure of the major product formed in the Friedel-Crafts alkylation of benzene with 1 -chlorobutane. 

Reaction of 2-methylpropene with benzene in the presence of H PO yields rcrr-butyl-benzene. Propose a mechanism for this reaction. 

Outline a synthesis of 2-methyH-phenylpropane (isobutylbenzene) starting from benzene using a Friedel-Crafts reaction. 

To this point, we have discussed only electropluhc substitution reactions of benzene itself. Now we will examine the effect that a substituent already bonded to the aromatic ring has on ring attack by an electrophile to attach a second substituent. For a substitution reaction on benzene, only one product results. But if a second substituent adds to a substituted benzene, any of three possible products—the ortho, meta, and para isomers—can result. We would bke to know how the original substituent affects (1) the rate of formation of these products and (2) how the substituent affects the product distribution. 

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