A method for promoting reaction events in ab initio molecular dynamics simulations that is explicitly based on the electronic structure is developed. The technique uses a bias potential that is added to the regular potential and is constructed from the HOMO-LUMO gap of the system. This bias potential is tested along predetermined reaction coordinates and through molecular dynamics simulations for several chemical reactions. The results indicate that the bias potential effectively reduces reaction barriers and can allow for the observation of a wide range of reactions that would not normally be observed through unbiased simulations. (C) 2003 Elsevier Science B.V. All rights reserved.