Self-condensation of propanol was carried out at atmospheric pressure over MgO as catalyst. The reaction gave 2-methylpentano, and propionaldehyde as the major products. The introduction of hydrogen before and during the reaction enhanced the catalyst selectivity to 2-methylpentanol. The effect of possible reaction intermediates on the catalyst selectivity and the mechanism of the reaction were investigated over MgO and indicated the important role of hydrogen transfer in the reaction. The highest selectivity (69%) was achieved in the presence of hydrogen at 450 degreesC with propanol conversion of 24%. (C) 2004 Elsevier B.V. All rights reserved.