Theoretical studies show that the systems NH₃·HCl and NH₃·H₂O form hydrogen bonded neutral molecule pairs, with no tendency to form ion pairs. However, formation of cubic arrays from (NH₃·HCl)₄ and (NH₃·HCl)(H₂O)₆ show only ion pairs and no neutral molecule adducts. In the case of cubic arrays of NH₃(H₂O)₇, we obtain formation of both neutral molecules and ion pairs for nine cubic structures out of a total of forty five that we have examined. There is a significant energy barrier between the neutral molecule adduct and the ion pair form in each case. These results provide a simple example to illustrate the importance of cooperative effects and solvation effects in determining the outcome of a chemical reaction.