While dimethylamine readily replaced ammonia, the reverse was not observed, indicating that substitution is driven by proton affinity and amine exchange is highly favorable. The measured rates were also independent of cluster size, and near unity uptake coefficients indicated that the conversion from ammonium to aminium salt clusters is likely rapid in ambient conditions. Similar results were obtained for the ammonium nitrate clusters, while ammonium methanesulfonate clusters showed slower exchange. Regardless of the acid in the cluster, amines will displace ammonia. Furthermore, the exchange of a surface ammonia was more rapid that the exchange of an ammonia at the core of the cluster. ) n (H 2 SO 4 ) s cluster systems, were in the low-pressure limit, and highly dependent on the reacting species and not on the pressure at which the reactions were monitored.