Deactivating groups, in electrophilic aromatic substitution

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

We recall that chlorine and bromine are deactivating groups in electrophilic aromatic substitution because they withdraw electron density by an inductive effect but are ineffective in the donation of electron density by resonance. The same features are important in controlling the rate of the second step of ketone halogenation. The bromine atom withdraws electron density from the carbonyl carbon atom, making the carbonyl oxygen atom less basic. Therefore, the enol forms more slowly in the second step. 

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