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The primary purpose of this work was to demonstrate the suitability of circular dichroism (CD) spectroscopy in stereochemical studies of α,β-unsaturated oximes, with particular emphasis on determination of E and Z geometry of the oxime double bond. As models for this study, O-phenyl and O-triphenylmethyl (trityl) oximes of 4-hydroxy-2-methylcyclopent-2-en-1-one were selected. These model compounds differ in both absolute configuration at C4 carbon atom and E-Z configuration of the oxime double bond. The basic dichroic technique applied was electronic circular dichroism (ECD) assisted by quantum-chemical calculations and vibrational circular dichroism (VCD) for selected cases. Such an approach enabled effective implementation of both goals. Thus, we were able to associate the signs of Cotton effects in the range of 190-240 nm with the absolute configuration at C4 and within 240-300 nm with the E- or Z-geometry of the oxime double bond. Within this work, optical activity of the protecting trityl group was also studied towards formation of the propeller-shaped conformations by using the same combined CD/DFT methodology. As shown, the helical structure of the trityl group has a considerable influence on the ECD spectra. However, the MPM and PMP conformers of the trityl group are in fact almost equally populated in the conformational equilibrium, making it impossible to distinguish them. On the other hand, rotamers of the hydroxyl group at C4 show a decisive impact on the VCD spectra in both phenoxy and trityl oximes., (© 2017 Wiley Periodicals, Inc.)

• Manuscript is research article. In this study, 12 oxime derivatives were synthesized by using with conventional method and microwave irradiation method. It was aimed to compare the effectiveness of the conventional method and microwave method. Their yields were determined for both methods, and the yields increased when the microwave method was used. The compounds which have oxime show geometric isomerism because they have carbon-nitrogen double bonds. Therefore, we have also aimed to evaluate their E / Z isomer ratios in this study. While the synthesized pyrazole derivative compounds were mostly obtained in Z isomer in both synthesis methods, it was observed that some of the title compounds were almost completely obtained as E isomers when the conventional synthesis method was used in the synthesized imidazole derivative compounds. The structures of synthesized compounds were confirmed by IR, 1 H -NMR, 13 C -NMR and HRMS spectra. Additionally, in this study, the HOMO-LUMO energies and thermodynamic properties of the E/Z isomers of 12 oxime derivatives were performed using the 6-31 * G basis set and the Density Functional Theory (DFT) calculation using the B3LYP method three different environments (water, ethanol, vacuum). In addition, geometric parameters such as chemical hardness (η), chemical potential (µ), electrophilicity index (ω) , chemical softness (σ) were calculated depending on the calculated HOMO-LUMO energies. [Display omitted] [ABSTRACT FROM AUTHOR]