The reactivity of isopropanol on polycrystalline Pt in acid solutions was investigated using in-situ Fourier transform IR spectroscopy (FTIRS) and on-line differential electrochemical mass spectrometry (DEMS). The electro-oxidation products are acetone and CO2; the former is observed when isopropanal is present in the bulk of the solution, and the latter is produced from strongly adsorbed species. Bath bulk and adsorbed isopropanol electro-reduction yield propane. H-D exchange is observed during propane formation when the reaction takes place in a D2O + DClO4 solution. This observation suggests the formation of adsorbates bonded to the surface through the C alpha atom of the isopropanol molecule. FTIR spectra of adsorbed species show the presence of -CH3 and -COH groups. The most probable adsorbate structures are (CH3-C-CH3)Pt, (CH3-CH-CH3)Pt and (CH3-COH-CH3)Pt, presumably accompanied by (CH3-COCH3)Pt.