Substituent Effects CO2H Y Ka pK -OH 3.3×10-5 4.48 Weaker -0CH3 3.5×10-6 4.46 Activating acid groups -CH3 4.3×10-6 4.34 -H 6.46×10-5 4.19 -C1 1.0×10-4 4.0 -Br 1.1×10-4 3.96 -CHO 1.8×10-4 3.75 Deactivating Stronger groups acid -CN 2.8×10-4 3.55 -N02 3.9×10-4 3.41 2004 Thomson/Brooks ColeSubstituent Effects