We present periodic density functional theory calculations on the adsorption modes of acetone over the (1 1 1) surface of Pt. The dominant species previously observed in low temperature HREELS and RAIRS experiments is an "end-on" eta(1) (O)-ketone and the calculated adsorption energy and vibrational frequencies for this species agree well with the literature data. The secondary species reported previously has been assigned to a eta(2)(C-2,O)-ketone with the molecular plane parallel to the surface. We show that this is an unlikely assignment and suggest an alternative enolate structure which has calculated vibrational frequencies in agreement with the spectra. The implications of the adsorption modes proposed in this work for models of the enantioselective hydrogenation of pyruvate esters are discussed. (c) 2005 Elsevier B.V. All rights reserved.