DFT calculations and microkinetic simulations are applied to the reproduction of previously reported experimental results on the evolution of product concentration versus time in the condensation reaction of n-butylamine and benzaldehyde. The mechanism is complicated by the role played by water impurities as proton shuttles. Several functionals and other approaches are tested, yet good agreement is only achieved upon the usage of an adjustment consisting of a directed biasing of the computed DFT free energies.