Figure 4. Current flow at different reaction time under various negative
external electric fields.
On the other hand, with the increase of the inhibiting electric
potential, decreased (S)-1-phenylethanol enantioselectivities were
observed. However, these changes in the enantioselectivity are probably
not due to the ability of OEEF to control reaction selectivity but are
more likely attributed to the catalyst decomposition. Figure 5 showed
the NMR analysis for the identification of the structures of the
catalysts before and after reactions. Samples 1 (spectrum A) and 2
(spectrum B) were obtained by dissolving the Ru catalysts in
CD3OD and reaction mixture (1-butanol and acetophenone
mixture) respectively, and peaks from the Ru catalyst are clearly
present at approximately 6.57 and 6.79 ppm. For sample 3 (spectra C),
collected from the reaction run at positive 15 V for 24 h, small signals
(due to the low initial concentration and difficulty of detection in 1H
NMR spectra) for the Ru catalyst can be seen. However, the NMR spectra
for sample 4, from the reaction run at negative 15 V for 24 h, showed no
signals for the Ru catalyst. It remains unknown if the decomposition of
the Ru catalyst was caused by the negative external electric field, and
further investigation is required.