Density functional theory is used to investigate the microscopic mechanisms of oxidation of propene (CH3-CH=CH2) to acrolein (CH2=CH-CHO) over iron antimony oxide (FeSbO4). Two routes for acrolein formation are investigated. The first starts from a chemisorbed state, in which propene binds with the surface via the pi orbitals: acrolein formation can be triggered first by the abstraction of an allylic H atom towards the active bridging O atom, followed by the abstraction of a second H atom toward either an O or an Sb atom and the subsequent desorption of the acrolein thereby formed. The second route starts from a direct dissociation of the propene molecule without the need to proceed through a chemisorbed precursor, which, however, is kinetically hindered. The first route is compared with the mechanisms proposed from experiment. We also discuss the mechanisms of propane oxidation to acrolein, in which propene oxidation is an important step. (c) 2008 Elsevier Inc. All rights reserved.