The influence of electron-withdrawing substituents on the adsorption of CO on copper

The chemisorption of carbon monoxide on Cu(100) in the presence of either methyl chloride or formic acid results in an increase in the the C---O stretching frequency to above the gas-phase value and a simultaneous increase in the heat of adsorption of CO. We explain this behavior qualitatively in terms of the simple Lewis acid/base character of both the surface and the adsorbate.