In order to determine the chemical mechanism for the (amm)oxidation of propane and propene on multimetal oxide (MMO) catalysts, we have carried out quantum mechanical (QM) calculations for model reactions on small clusters that we have used to train the parameters for the ReaxFF reactive force field, which enables molecular dynamics (MD) simulations for reactions on the complex reconstructed surfaces of MMO. We report here insights from the QM on the reaction mechanisms of selective (amm)oxidation of propene on bismuth molybdate catalysts and the oxidative dehydrogenation of propane on vanadium oxide catalysts. We also report the application of ReaxFF to predict the stable surfaces of the M1 phases of the MoVTeNbO catalysts.