Several methods for determining solvation free energiesare compared for the formation of a zwitterionicintermediate between methylamine and formaldehyde. While in thegas phase no minimum exists for C−Nseparations less than that found in the van der Waals complex, allmethods examined here for determiningthe solvation free energy predict a stable zwitterionic minimum.The most stable minimum exists using thepolarized continuum model (PCM). The finite differencePoisson−Boltzmann method yields comparableresults when parameters from a solvent interaction potential are used.A stable zwitterion was also foundwhen two explicit molecules of water were included.