An approach termed temporal quantum mechanics/molecular mechanics is presented to extend the time scales accessible in molecular dynamics simulations of reactions. This approach employs a hierarchy of methods: force-fields (FFs) to simulate the system near potential energy minima, semi-empirical (SE) molecular orbital methods to assess the likelihood of trajectories overcoming reaction barriers, and quantum chemical (QC) methods to model changes in bonding and electronic structure during reactions. This method relies primarily on FFs and SE methods, providing access to much longer time scales than those accessible using QC methods alone, with the targeted use of QC methods ensuring reactive events are described properly. (C) 2011 Elsevier B. V. All rights reserved.