A series of substituted anthraquinones has been prepared to determine the influence of hydrophilic and hydrophobic substituents on the efficiency of delignification in soda pulping of Douglas fir. Regardless of redox potential and proximity to the ring system of the parent anthraquinone, carboxyl groups strongly diminish the activity of AQ. This effect is believed to be the result of increased hydrophilicity of the carboxyl derivatives relative to unsubstituted anthraquinone. Conversely, nonpolar hydrocarbon sidechains tend to increase the activity of anthraquinone in soda pulping. These effects suggest that adsorption phenomena may play a strong role in additive performance, and that hydrophobic substituents tend to concentrate the additive in the wood phase, while hydrophilic derivatives tend to remain in the liquid phase.