Selected results concerning the acetone conversion to methyl isobutyl ketone promoted by mechanical energy are presented. Cu-MgO composites at different Cu contents and amorphous Cu40Mg60, prepared by different ball milling techniques, were employed as solid substrates for the mechanochemical process. The conversion and selectivity values of the acetone transformation were followed under Ar and H-2 reaction atmosphere and as a function of the impact energy. The mechanical treatment under H-2 resulted mainly in acetone hydrogenation leading to 2-propanol, while under Ar, the formation of diacetone alcohol, mesityl oxide and methyl isobutyl ketone (MIBK) was observed. Conversion changes and selectivity shifts were observed depending on the substrates employed, and the largest amount of MIBK; was obtained when amorphous Cu40Mg60 was used. An important structural transformation occurred during the mechanochemical runs. (C) 1999 Elsevier Science S.A. All rights reserved.