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SolutionsThe Third SEAr

1. Disubstituted benzenes

Predict the result of the following reactions:

Five reactions: alkylation of 4-isopropoxytoluene with cyclopentanol and BF₃, chlorination of 3-cyclohexyltoluene, 1-indanone with MeBr/AlBr₃, nitration of 1-methoxy-7-nitronaphthalene and sulfonation of 1-chloroanthrone
Products: cyclopentyl enters ortho to the isopropoxy group; chlorine para to the methyl; methyl at position 6 of indanone, meta to the carbonyl; nitro at position 4 of the methoxy-bearing ring; and SO₃H on the ring without chlorine, meta to the carbonyl
  • The most activating group wins: isopropoxy over methyl, and methyl over cyclohexyl, because of steric hindrance.
  • In indanone the carbonyl directs meta and the CH2 ortho-para: both influences coincide at position 6.
  • In naphthalene the ring activated by the methoxy group reacts, at the free α position.
  • In anthrone the ring not deactivated by chlorine is substituted.

2. Directing power

Rank these substituents in order of decreasing directing power: –CH3, –OH, –NO2, –Cl, –NHCOCH3.

–OH > –NHCOCH3 > –CH3 > –Cl > –NO2. When two groups compete, the more activating one wins.

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