Substitution, electrophilic deactivating groups

The pKa of p-(tiifluoromethyl)benzoic acid is 3.6. Is the trifluoromethyl substituent an activating or deactivating group in electrophilic aromatic substitution ... 

Deactivating group (Section 16.4) An electron-withdrawing substituent that decreases the reactivity of an aromatic ring toward electrophilic aromatic substitution. 

Answer The Br is a deactivating group and will direct electrophilic substitution to the desired position. Thus the -OCHj group should be put on the ring next. Let us use CHaNa which will require the naphthol C. 

A second limitation is that aromatic compounds substituted with moderately or strongly deactivating groups cannot be alkylated. The deactivated ring is just too poor a nucleophile to react with the unstable carbocation electrophile before other reactions occur that destroy it. 

Energy profiles with a deactivating group. Nitrobenzene is deactivated toward electrophilic aromatic substitution at any position, but deactivation is strongest at the ortho and para positions. Reaction occurs at the meta position, but it is slower than the reaction with benzene. 

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