FT-IR, FT-Raman, UV–Vis, NMR and structural studies of carquejyl acetate, a distinctive component of the essential oil from Baccharis trimera (less.) DC. (Asteraceae)

Structural and vibrational studies of equilenin, equilin and estrone steroids

“…Moreover, in equilin the presence of a C=C in the B ring increase the number of C=C increasing the corresponding force constant to 6.86 mdyn Å -1 . The force constants predicted for the three species present value similar to the observed in other species containing similar groups [32,[34][35][36][37][38][39][40][41][48][49][50][51][52][53][54].…”

“…A careful detail of the assignments of those modes for the three species can be seen in Table 7 where the most intense bands are assigned to the C=O and C=C stretching modes. Hence, the intense IR and Raman bands between 1751 and 1496 cm -1 can be easily assigned to the C=O and C=C stretching modes corresponding to the three species, as reported for species containing these groups [34][35][36][37][38][39][40][41]. Obviously, those C=O and C=C bonds present double bond characters and, for these reasons, their vibration modes are observed at higher wavenumbers but, the C-C bonds with partial double bond characters are predicted at lower wavenumbers, thus, they can be assigned between 1454 and 1325 cm -1 , as observed in Table 7.…”

“…Here, the assignments oh three species were performed considering the corresponding normal internal coordinates, transferable scaling factors and only contributions ≥ 10%. In addition, the frontier orbitals and some remarkable descriptors were used to predict reactivities and behaviours of three species [31][32][33][34][35][36][37][38][39][40][41]. The predicted Raman spectra in activities were converted to intensities for a better correlation with the experimental one [42,43].…”

“…Another form different of analyzing the stabilities of these species is through of the Bader's theory of atoms in molecules (AIM) where is possible to examine possible H bonds and/or intra-molecular interactions by using the topological properties with the AIM2000 program [46,47]. This study request the calculations of electron density, (r), the Laplacian values,  2 (r), the eigenvalues (1, 2, 3) of the Hessian matrix and, the |λ1|/λ3 ratio in the bond critical points (BCPs) and ring critical points (RCPs) by using the B3LYP/6-31G* method, according to other species with different rings [32][33][34][35][36][37][38][39][40][41][42]. The results for equilenin, equilin and estrone in gas phase species are presented in Table 5.…”

“…The frontier orbitals are parameters frequently used in the determination of gap values, as suggested by Parr and Pearson [31], because from their differences can be predict the reactivities and, also, with the gap values it is possible to calculate some descriptors of great interest to predict the behaviours of species in different media [32][33][34][35][36][37][38][39][40][41]. Hence, the frontier molecular HOMO and LUMO orbitals, gap values and the chemical potential (μ), electronegativity (χ), global hardness (η), global softness (S), global electrophilicity index (ω) and global nucleophilicity index (E) descriptors of equilenin, equilin and estrone in gas phase by using the B3LYP/6-31G* method are summarized in Table 6.…”