Ph. D. THESIS 2009

Scheme 9
This equilibrium was investigated using 1 H NMR spectra. The experiments
were based on the differences of the chemical shifts for the equatorial protons
at positions 2,4,6,8 belonging to the syn (4e,6e = 3.48 ppm) and to the anti
isomers (2e,6e = 3.36 ppm).
Figure 23. Part 1 H-NMR spectrum of a crude mixture of syn and anti isomers of
dioxime 5
The experiments were run starting from either the pure syn or anti
isomers and were based on the recording of the 1 H NMR spectra of the same
sample over several periods of time and on the measuring in these spectra of
the ratios between the isomers using the intensities of their specific signals
(Figures 24 and 25).
33