The adsorption of acetone on the Si(0 0 1) surface was investigated using the first-principles pseudopotential method within a generalized gradient approximation to the density functional theory. Our results indicate that [(CH3)(2)CO] adsorbs at low temperature in a [2 + 2] cycloaddition reaction via C = O radical to the dangling bonds of Si-Si dimers. The dissociation and desorption of the methyl and acetyl radicals was also investigated, pointing out that the most probable dissociation occurs with the formation of a CH2-CH2 structure over a Si-Si dimer and with the saturation of the other dimer by hydrogen atoms in a (2 x 2) reconstruction, and the desorption of a C = O molecule. Calculated vibrational modes for the adsorbed systems are presented, with a view to contribute to further experimental investigations. (C) 2004 Elsevier B.V. All rights reserved.