Double proton transfers in dimers of orthophosphoric, sulfuric, and perchloric acids and in their associates with water molecules

Mechanisms of proton transfer in the dimers of orthophosphoroc, sulfuric, a nd perchloric acids and in their associates with water molecules were studi ed by MP2(fc)/6-31G** ab initio calculations. It was shown that in all thes e systems occurs cooperative (concerted or single-stage) transfer of two pr otons. The calculated activation barriers of cooperative proton transfer in the associates are equal to 9.1, 8.7 and 10.3 kcal/mol, respectively, and in the dimers these values are -0.01, 4.9, and 10.3 kcal/mol. The calculate d results show that with increasing strength of H bonds in the system the b arrier to double proton transfer decreases.