The pK_a?s of five p-substituted benzoic acids (YC₆H₄CO₂H) follow. Rank the corresponding substituted benzenes (YC₆H₅) in order of their increasing reactivity toward electrophilic aromatic substitution. If benzoic acid has PK_a = 4.19, which of the sub-stituents are activators and which arc deactivators?

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-CO2H Substituent Y pka of Y- -si(CH3)3 4.27 -CH=CHC=N 4.03 -H9CH3 4.10 -OS02CH3 3.84 -PCI2 3.59