Reactivity trends for oxidation of various alcohols and polyols have been examined for carbon-supported Au, Pd, and Au-Pd catalysts. A Hammett sigma I approach was used to study substituent effects, with Hammett factors (rho) of 1.27, 1.31, and 0.40 obtained for Pd, Au, and Au-Pd catalysts, suggesting the formation of a net negative charge at the transition state of the rate limiting step. The lower rho for the Au-Pd catalyst versus Au and Pd monometallic catalysts indicates the ability of the Au-Pd catalyst to stabilize the negative charge at the transition state, explaining the improved performance of Au-Pd bimetallic catalysts for alcohol oxidation. Hammett-Taft factors were used to explain the low selectivity of terminal diols and polyols to diacids.