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 contrib ute to differences in proton solvation energies: hydrogen-bond cleavage, ch anges in hydrogen-bond lengths, and proton delocalization. These factors ar e estimated from experimental attributes. In dilute acidic aqueous solution s H3O+ is more stable than H5O2+ by about 0.6 kcal/mol. This estimate, toge ther with the activation energy for proton mobility, supports the 121 mecha nism 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.