Electronic structure calculations were performed for water and methanol adsorbed onto model structures for ideal (110) and (100) rutile TiO2 surfaces. Both molecular and dissociated forms of water and methanol were examined for each surface, and the reaction coordinate for interconversion of the two forms. Our results indicate a strong thermodynamic favor for the dissociative form in each case; however, there is a potential energetic barrier to proton transfer to generate the dissociative form for the (110) surface. Based upon the structural differences between these surfaces, it is proposed that multiple hydrogen bonding interactions with the adsorbed species facilitate proton transfer.