Proton Solvation and Proton Mobility

Experimental evidence for proton solvation and proton mobility is analyzed and the results are compared with recent simulations. Three factors contribute to differences in proton solvation energies: hydrogen‐bond cleavage, changes in hydrogen‐bond lengths, and proton derealization. These factors are estimated from experimental attributes. In dilute acidic aqueous solutions H 3 O + is more stable than H 5 O 2 + by about 0.6 kcal/mol. This estimate, together with the activation energy for proton mobility, supports the 121 mechanism for proton mobility in which a protonated water monomer is transformed, by second‐shell hydrogen‐bond cleavage, to a protonated dimer and back to another protonated monomer.