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J. Phys. Chem. 1991, 95, 10407-10413 10407 Excited-State Proton Transfer to Methanol-Water Mixtures
 

Summary: J. Phys. Chem. 1991, 95, 10407-10413 10407
Excited-State Proton Transfer to Methanol-Water Mixtures
Noam Agmon,*
Department of Physical Chemistry and The Fritz Haber Research Center, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel
Dan Huppert, Asnat Masad,
School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences,
Tel Aviv 69978, Israel
and Ehud Pines
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue,
(Received: April 2, 1991)
Tel Aviv University,
Chicago, Illinois 60637
We have measured the fluorescence decay of I-hydroxypyrene-1,3,6-trisulfonatedue to proton transfer to solvent in
water-methanol mixtures. The data agree quantitativelywith the reversible,diffusion-influencedproton-transfer mechanism
in all solutions. No significant deviations from a short-time exponential decay or a long-time power law decay were found
that could support a recently suggestedwater moleculediffusionmechanism. Solvent-inducedvariationsin the deprotonation
rate coefficient are very close to those in the corresponding equilibrium coefficient. Analysis of measured and literature
pK data indicates that the composition dependence is mainly due to localized counterion stability in water-rich solutions
and to proton stability in methanol-rich solutions. Quantitative agreement with literature compilations of proton-transfer

  

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

 

Collections: Chemistry