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Science 18 July 2003:
Vol. 301. no. 5631, pp. 349 - 352
DOI: 10.1126/science.1085762
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Reports

Real-Time Observation of Bimodal Proton Transfer in Acid-Base Pairs in Water

Matteo Rini,1 Ben-Zion Magnes,2 Ehud Pines,2* Erik T. J. Nibbering1*

The neutralization reaction between an acid and a base in water, triggered after optical excitation, was studied by femtosecond vibrational spectroscopy. Bimodal dynamics were observed. In hydrogen-bonded acid-base complexes, the proton transfer proceeds extremely fast (within 150 femtoseconds). In encounter pairs formed by diffusion of uncomplexed photoacid and base molecules, the reaction upon contact was an order of magnitude slower, in agreement with earlier reported values. These results call for a refinement of the traditional Eigen-Weller picture of acid-base reactions: A three-stage model is introduced to account for all observed dynamics.

1 Max Born Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, D-12489 Berlin, Germany. 2 Department of Chemistry, Ben-Gurion University of the Negev, Post Office Box 653, Beer-Sheva 84105, Israel.

* To whom correspondence should be addressed. E-mail: epines{at}bgumail.bgu.ac.il (E.P.); nibberin{at}mbiberlin.de (E.T.J.N.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Sequential Proton Transfer Through Water Bridges in Acid-Base Reactions.
O. F. Mohammed, D. Pines, J. Dreyer, E. Pines, and E. T. J. Nibbering (2005)
Science 310, 83-86
   Abstract »    Full Text »    PDF »
Spectral Signatures of Hydrated Proton Vibrations in Water Clusters.
J. M. Headrick, E. G. Diken, R. S. Walters, N. I. Hammer, R. A. Christie, J. Cui, E. M. Myshakin, M. A. Duncan, M. A. Johnson, and K. D. Jordan (2005)
Science 308, 1765-1769
   Abstract »    Full Text »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)