Frankfurt 2006 – scientific programme

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MO: Molekülphysik

MO 41: Hauptvortr
äge

MO 41.3: Invited Talk

Wednesday, March 15, 2006, 11:40–12:10, H12

o-Nitrobenzaldehyde: A "Tool” to study Hydrogen Transfer Reactions, Nucleophilic Additions, and Eliminations — •Peter Gilch, Hilmar Schachenmayr, Wolfgang Schreier, and Stefan Laimgruber — Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 München, Germany

Upon light absorption o-nitrobenzaldehyde is transformed into o-nitrosobenzoic acid. Although this reaction has first been described more than 100 years ago it is only now that by femtosecond vibrational spectroscopy intermediates of this reaction have been unequivocally identified [1]. The excitation of NBA initiates a hydrogen transfer which within 400 fs results in the formation of a first ground state intermediate - a ketene. This ketene has been observed via femtosecond IR spectroscopy. The ketene is subject to a nucleophilic addition occuring with a strongly solvent dependent reaction time (with time constants of ∼ 10 ps – 2 ns). In protic solvents the reaction takes place while the ketene is still vibrationally hot which results in non-exponential kinetics. The product of the addition is characterized by IR and stimulated Raman spectroscopy. It transforms into the final nitroso product via an elimination. Thus, NBA allows to study at least three elementary reaction types of organic chemistry.

[1] S. Laimgruber et al., Angew. Chem. Int. Ed. 44 (2005) 7901.