## 3 Obtained Results and Their Discussion  
In this study, we logically continued to investigate the conformational mobility [16; 17; 18] of the quercetin molecule and extend this approach to the rotations of the hydroxyl groups in the 3' and 4' positions, which are carefully presented in Tables 1-3 and Figures 1-3. The most obvious methods of the conformational interconversions between the 48 conformers [16] of the quercetin molecule were considered and investigated in detail through the rotations of the O3'H and O4'H hydroxyl groups around the exocyclic C-O covalent bonds. In this case, the TSs have been formed gradually, starting from the 48 conformers of the quercetin molecule [16] by the single or concerted rotations of the O3'H and O4'H hydroxyl groups--designated as TS\({}^{\text{O3'H}}\), TS\({}^{\text{O4'H}}\), and TS\({}^{\text{O3'H/O4'H}}\), respectively. Therefore, detailed analysis of the obtained results enabled us to obtain the following observations and their discussion. As individual, the concerted rotational transitions of the O3'H and O4'H hydroxyl groups proceed through the mirror-symmetrical pathways, which are controlled by the mirror-symmetrical TSs. Totally, we have revealed 48 TSs--16 TSs in each case (Figures 1-3; Tables 1-3). Individual conformational transitions are controlled by the non-planar TS\({}^{\text{O3'H}}\) and TS\({}^{\text{O4'H}}\) (C\({}_{1}\) point symmetry) with non-orthogonal structure (see HO3'C3'C2'(78.7-83.3 degree) and HO4'C4'C5' (80.2-82.1 degree) dihedral angles in Tables 1 and 2 and Figures 1 and 2). Their non-orthogonal structure, most probably, could be connected with the non-symmetrical surrounding of the free electronic pairs of the oxygen atoms of the hydroxyl groups. The TSs for the concerted conformational transformations--TSs\({}^{\text{O3'H/O4'H}}\)--possess non-planar structure in the case of the planar conformers **1-12**, **19**, **21**, **22**, **25**, **27**, **28**, and **31-36** and local non-planar structure for the non-planar conformers, **13-18**, **20**, **23**, **24**, **26**, **29**, **30**, and **37-48**, which mutually interconvert (Figure 3, Table 3). Gibbs free energies of activation for these processes form the following order; \(\Delta\Delta\text{G}_{\text{TS}}{}^{\text{O4'H}}\) (3.33-7.05) \(<\Delta\Delta\text{G}_{\text{TS}}{}^{\text{O3'H}}\) (4.23-7.08) \(<\Delta\Delta\text{G}_{\text{TS}}{}^{\text{O3'H/O4'H}}\) (4.41-7.56 kcal-mol\({}^{-1}\) under normal conditions) (Tables 1-3). The imaginary frequencies are in the following ranges: 366.7-391.5 (TS\({}^{\text{O3'H}}\)), 328.8-363.5 (TS\({}^{\text{O4'H}}\)), and 454.5-483.1 (TS\({}^{\text{O3'H/O4'H}}\)). Without exception, 48 conformers of the quercetin molecule have been established to be the dynamically stable structures, based on the investigated conformational transitions. During their lifetime (\(\tau=(1.05-2.53)\cdot 10^{-11}\) s) (Tables 1-3), the lowest frequency intramolecular vibrations can occur [16]. It is a characteristic feature that investigated conformational transitions are dipole-active, as they cause the changing of the dipole moment by the absolute value, so by the spatial orientation, and practically do not disturb the structure of the quercetin molecule and physico-chemical characteristics of its specific intramolecular interactions. Even the energy of the intramolecular C2'/C6'H... O3 and O3H... C2'/C6'H H-bonds between the B and C rings (Figures 1-3) change at these conformational transitions by no more than on \(\sim\)4.7%. Interestingly, concerted conformational transitions, which are controlled by the TSs\({}^{\text{O3'H/O4'H}}\), proceed without intermediates on the hyperspace of the Gibbs free energy. Moreover, we did not register any specific intramolecular interactions in the B ring of the quercetin molecule at the conformational motions of the O3'H and O4'H hydroxyl groups.