Investigation of Hyperconjugation by UV-Photoelectron Spectroscopy

Investigation of Hyperconjugation by UV-Photoelectron Spectroscopy

Author: ChemPlusChem

In organic chemistry, hyperconjugation is responsible for a variety of phenomena, including the anomeric effect, gauche effect, β-silicon effect, stability of carbocations and free radicals.

To visualize the effects of hyperconjugation, Akira Sekiguchi, University of Tsukuba, Japan, and colleagues synthesized tetrakis(trimethylsilyl)tetrahedrane 1 and its pentafluorophenyl derivative 2 and recorded their ultraviolet photoelectron spectra (UV-PES).

The observation of an energy gap of 2.0 eV between the first and fourth ionization bands of 2 provides clear-cut evidence for the σtetrahedrane–πarene orbital interaction (neutral hyperconjugation). This nicely supports the preliminarily proposed neutral hyperconjugation in 2, which was based on structural and spectroscopic data.

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