Time-resolved resonance Raman study of the structure and reactions of benzoate electron-adducts in water

PHYS 399

Deanna M O'Donnell, dsheeha1@nd.edu, Department of Chemistry and Biochemistry and Notre Dame Radiation Laboratory, University of Notre Dame, Notre Dame Radiation Laboratory, Notre Dame, IN 46556 and G. N. R. Tripathi, Tripathi.1@nd.edu, Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556.
Short-lived radical states of benzoate anion, which is used as a food preservative, have been examined by transient absorption and time-resolved resonance Raman spectroscopies. These studies are aimed to provide an understanding of the reaction paths that convert the benzoate anion into benzene, a known carcinogen. Electron addition to the benzoate anion in water produces a dianion radical which is structurally stabilized by hydration and absorbs at ~ 440 nm. The thermally activated electron loss from the radical occurs at the millisecond time scale. The carboxylate CO bonds are considerably weakened on radical formation. The dianion radical reacts with water at a fairly high rate (reaction period ~ 10 ns) and converts into the monoanion radical with a small (~ 10 nm) blue shift in the absorption maximum. The resonance Raman spectra of the two radicals are drastically different. The reduced radical states of the benzoate anion in water are unusual as they undergo fast photochemistry that competes with Raman scattering.
 

PHYS Poster Session - General Experiment
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008