1. Reversible Photoisomerization of β-Methyl-β-Nitrostyrene: The Role of Triethylamine
- Author
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Ester Norambuena, C. Giannotti, and E. A. Lissi
- Subjects
Photoisomerization ,Chemistry ,Quantum yield ,Photochemistry ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry ,law.invention ,Electron transfer ,chemistry.chemical_compound ,Unpaired electron ,law ,Nitro ,Electron paramagnetic resonance ,Triethylamine ,Spectroscopy ,Cis–trans isomerism - Abstract
The photolysis of trans-β-nitro-βmethylstyrene in acetonitrile solution gives the cisisomer with a quantum yield of 0.8. Addition of triethylamine to the system leads to a small decrease in the photoisomerization quantum yield and the appearance of a strong EPR signal. This signal remains for several hours at the end of the irradiation. It is demonstrated that the EPR signal is associated to an intermediary produced during the triethylamine catalyzed thermal back formation of the trans isomer. This intermediary bears an unpaired electron mostly associated to the nitro group and suggest that the thermal back reaction takes place by an initial electron transfer from the amine to the nitro group, leading to a long lived zwitterionic biradical.
- Published
- 2000