Caught in action: Observation of hydrolysis reactions in hydrated multiply charged anions, [A]x-(H2O)n --> [HA](x-1)–(H2O)n-1OH–

PHYS 313

Lai-Sheng Wang, ls.wang@pnl.gov, Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99354
The conjugate bases of polyprotonic acids are multiply charged anions (Ax–) and can undergo hydrolysis reactions in aqueous solutions (Ax– + H2O --> HA(x-1)– + OH–), constituting the most fundamental acid-base chemistry. We report the first observation of hydrolysis reactions in hydrated sulfate clusters, SO42–(H2O)n, in a low temperature ion trap using photoelectron spectroscopy. Low-temperature photoelectron spectra of SO42–(H2O)n show a weak low binding energy feature due to HSO4–(H2O)n-1OH–, which is formed during ion trapping and cooling. The hydrolysis product HSO4–(H2O)n-1OH–, involving two distinct anions stabilized by solvation, is metastable and can only be observed at very low trapping temperatures. For SO42–(H2O)6, temperature-dependent studies show that the hydrolysis product HSO4–(H2O)5OH– disappears at a trapping temperature of 40 K, yielding an estimated coulomb explosion barrier height on the order of a kcal/mol. The hydrolysis reaction is observed to strongly depend on the degree of hydration.
 

Hydration: From Clusters to Aqueous Solution
1:20 PM-5:00 PM, Wednesday, August 22, 2007 BCEC -- 159, Oral

Division of Physical Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007