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Primary events in photoacid dissociation Department of Physical Chemistry and the Fritz Haber Research Center, \Lambda

Summary: Primary events in photoacid dissociation
Noam Agmon
Department of Physical Chemistry and the Fritz Haber Research Center, \Lambda
The Hebrew University, Jerusalem 91904, Israel
Postulated hydrogen­bond rearrangements accompanying photoacid excitation and disso­
ciation are identified. Experimental evidence corroborating these suggestions is surveyed.
Acid dissociation is one of the more fundamental chemical reactions [1,2]. Strong gaseous
acids which dissociate in clouds and at the surface of startospheric ice participate in the
mechanisms producing acid rain and the ozone hole. Weaker acids function as buffers
that determine the pH of the environment in which we live. Acids can catalyze a variety
of important reactions. At metallic surfaces, proton concentrations determine corrosion
rates. In living cells, they take part in enzyme action and in the storage and utilization of
energy. Proton concentrations in vivo are carefully regulated, through varied mechanisms
such as proton carriers and proton pumps. A relatively small decrease in the working pH
value can make an organism much more susceptible to bacterial attacks.
In spite of its fundamental role in chemistry and biology, the molecular mechanism of
acid dissociation is poorly understood, and only few bulk phase simulations have been
performed [3--5]. We are particularly interested in the role of the solvent, e.g. water,
in promoting acid dissociation and in the hydrogen­bond (HB) rearrangements which


Source: Agmon, Noam - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry