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MO: Molekülphysik

MO 23: Photochemistry

MO 23.5: Vortrag

Dienstag, 14. März 2006, 15:00–15:15, H12

Time Resolving a Nucleophilic Addition — •Laimgruber Stefan, Hilmar Schachenmayr, Wolfgang Schreier, and Peter Gilch — Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 München, Germany

Nucleophilic additions to double bonds are among the most important elementary reactions in organic chemistry. Detailed mechanistic informations on these reactions are difficult to obtain. They usually proceed thermally and are therefore not accessible by femtosecond spectroscopy. During the photoreaction of o-nitrobenzaldehyde to o-nitrosobenzoic acid a ketene intermediate is formed [1]. The formation of this ground state species is ultrafast (∼ 400 fs) and its formation time is hardly affected by the solvent. Thanks to this fast formation a nucleophilic addition to the ketene can easily be time resolved. We monitored the kinetics of this addition by means of visible and vibrational femtosecond spectroscopy and observed reaction times ranging from 10 ps to some nanoseconds depending on the solvent used. Based on these findings conclusions on the mechanism of the addition will be presented.

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