Effect of Water Activity on the Rate of Proton Dissociation

D. Huppert*, E. Kolodney, M. Gutman, E. Nachliel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The rate of proton transfer from electronically excited aromatic alcohols to the solvent was measured by both steady-state and time-resolved picosecond fluorimetry. In concentrated solutions (1–6 M) of strong electrolytes (LiBr, LiClO4, NaCl, NaClO4, KCl, MgCl2, MgClO4) at pH ≫ pK*, the rates measured by the two methods were identical. The rate of dissociation decreases upon increasing the concentration of the salt. Results obtained with different salts fit a single straight line when the log of the rate constant is drawn vs. the log of water activity. Such measurements are suitable for accurate determination of a(H2O) of concentrated solutions of strong electrolytes. It is proposed that the rate of proton dissociation is related to the free energy of proton hydrate formation.

Original languageEnglish
Pages (from-to)6949-6953
Number of pages5
JournalJournal of the American Chemical Society
Issue number25
StatePublished - 1982


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