Ketonization turnovers occur on TiO or ZrO pairs saturated with monodentate carboxylates. Turnover rates benefit from intermediate strength of acid and base sites and distances that enforce orbital overlap. Inactive bidentate carboxylates form slowly and cause site blocking. Ketonization is limited by CC coupling of 1-hydroxy enolates with monodentate carboxylates. The CC coupling transition state is preferentially stabilized by H-bonds at high coverages.