Carbon 1s electron binding energies determined by X-ray photoelectron spectroscopy and mean dipole moment derivatives obtained from experimental infrared intensities are shown to be related through the simple potential model proposed by Siegbahn and collaborators. The sp3 carbon atoms in 13 halomethanes, 2 ethanes, 3 methylacetylenes, cyclopropane, and ethylene oxide have 1s energies, which, after correction for electrostatic potentials from neighboring atoms, are linearly related to the carbon mean dipole moment derivatives, presenting a slope of 15.50 ± 0.29 eV/e. The sp2 carbons of ethylene, three haloethylenes, and three carbonyl compounds also exhibit a linear relationship having a significantly different slope of 17.37 ± 0.87 eV/e. The sp carbon atoms in acetylenes, cyanides, CO, CS2, CO2, and OCS show a third linear relationship, with a slope of 18.90 ± 0.75 eV/e. These slopes are proportional to the inverse atomic radii of sp3, sp2, and sp carbon atoms and according to the simple potential equation can be interpreted as estimates of Coulomb repulsion integrals involving these hybridized orbitals and the 1s core electron orbitals. Two basic assumptions of the potential model are investigated. The effect of relaxation energies on the 1s electron ionization processes is estimated as the difference between ΔSCF ionization energies and Koopmans' frozen orbital estimates obtained from 6-31G(d,p) wave functions. These results are compared with values obtained previously from the equivalent cores estimating procedure. Also the conceptual validity of identifying the carbon mean dipole moment derivatives as atomic charges is discussed within the framework of the charge−charge flux-overlap model.

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A green solvent-based optimization for rosmarinic acid (RA), carnosol (COH), and carnosic acid (CA) extraction, the three main antioxidants from rosemary, was performed. The conventional solid-liquid extraction was optimized using a central composite design (CCD) followed by the desirability approach. In the CCD analysis the quantitative effects of extraction time (4.8-55.2min), liquid-to-solid ratio (4.6-21.4mLg(-1)), and ethanol content (44.8-95.2% v/v) were determined for the extracted amount of antioxidants, their concentrations in the extract, and the extraction yield. Samples were analyzed by HPLC and the antioxidants were identified by comparison with pure standard retention times and UV spectra. The desirability function that simultaneously maximizes the antioxidants extraction and their concentrations in the final product was validated. The extraction using a hydroalcoholic solution 70% v/v, at low liquid-to-solid ratio (5mLg(-1)), and after 55-min yielded an antioxidant recovery rate of 89.8%, and a final product 4.75 times richer in the main antioxidants than the raw material.

Mean dipole moment derivatives determined from gas-phase infrared fundamental intensity data for 30 molecules are compared with Generalized Atomic Polar Tensor (GAPT) charges calculated from wave functions obtained with 6-31G(d,p) and 6-311++G(3d,3p) basis sets at the Hartree-Fock, B3LYP density functional, and MP2 electron correlation levels. With very few exceptions, the MP2 results are in better agreement with the experimental values than are the B3LYP results calculated with the same basis set, although the differences between these calculated results are often small. The Hartree-Fock results deviate most from the experimental values. For all atoms studied here, C, H, F, Cl, N, O, and S, the MP2/6-311++G(3d,3p) results agree most closely with the experimental values with rms errors of 0.059, 0.013, 0.044, 0.045, 0.030, 0.041, and 0.014e respectively. Although the calculated results for charges between -0.5 and +0.5e seem to deviate randomly from the experimental results, calculated charges ranging from +0.5 to +2.0e tend to be slightly larger than the experimental values. This is a consequence of the fact that the MP2/6-311++G(3d,3p) calculations tend to overestimate infrared intensity sums for molecules with more polar bonds and intensity sums above 500 km mol -1 . The results reported here show that the calculated charge values seem to be converging to the experimental values as the basis set becomes more extensive, 6-31G(d,p) to 6-311++G(3d,3p), and as the electron correlation level becomes more complex, Hartree-Fock to B3LYP density functional to MP2. Experimental mean dipole moment derivative values are shown to be consistent with trends in atomic charge values expected from chemical arguments for the halomethanes, hydrocarbons and Group IV hydrides.

The simple potential model has been shown to be useful in relating core electron binding energies measured in the X-ray region with mean dipole moment derivatives obtained from experimental infrared vibrational intensities. The importance of including relaxation corrections to the experimental 1s ionization energies of sp, sp 2 , and sp 3 hybridized carbon atoms are investigated here. Although relaxation energies obtained from 6-31G(d,p) and 6-311++G(3df,3p) basis sets using ∆SCF calculations show differences of about 1 eV for most molecules studied, relative differences are of the order of 0.1 eV. Exceptions are the CO, CO 2 , COS, and CS 2 molecules where discrepancies are larger. Relaxation energy corrections improve simple potential model fits with mean dipole moment derivatives for all carbon atom models but is most pronounced for the sp hybridized atoms. The simple potential model corrected for relaxation energies is investigated as a criterion for testing the quality of Mulliken, CHELPG, Bader and GAPT carbon atomic charges calculated from MP2/ 6-311++G(3d,3p) wave functions. The GAPT charges are in excellent agreement with the experimental mean dipole moment derivatives (within 0.067e) and provide superior statistical fits to the simple potential model when compared with those obtained for the other charges.

Principal component analysis is used to compare polar tensors of CH4, SiH4, GeH4, and SnH4 and their completely deuterated analogues determined from infrared fundamental gas-phase intensities measured in different laboratories. This analysis also includes theoretical polar tensor values obtained from effective core potential universal basis set calculations as well as from MP2/6-311++G(3d,3p) functions for CH4, SiH4, and SiF4. Theoretical values are also used to resolve sign ambiguities in the dipole moment derivatives of SiF4. Preferred polar tensor values are proposed for all these molecules. Mean dipole moment derivatives for SiH4 and SiF4 are related to the 2p core ionization energies using the simple potential model proposed by Siegbahn and collaborators. These results are confirmed by MP2/6-311++G(3d,3p) calculations for these molecules and for SiH3F, SiH2F2, and SiHF3. This study is extended to the fluorogermanes using experimental 3p and 3d core electron ionization energies and mean dipole moment derivatives calculated from MP2/A-VDZ/6-311++G(3d,3p) wave functions. The simple potential model interpretation of mean dipole moment derivatives as atomic charges implies that the silicon charge, ±0.904e, is slightly higher than the germanium charge of ±0.862e.

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The CIS and EOM-CCSD adiabatic geometries for the first excited states of a set of small molecules (C2H4, C2H2, H2C=O, H2C=S, CS2, CO2, SO2, NO2) have been calculated using the 6-311++G** basis set to see if the former geometries can be good starting points for optimizations at the latter theoretical level. With most of the molecules, there is fairly good agreement between the results from the two methods, and EOM-CCSD gives good agreement with the available experimental data. A detailed discussion of the lowest-lying singlet excited states in CO2 and CS2 is presented, highlighting the pronounced differences in electronic character and equilibrium structure displayed by these isovalent species. The origins of the structural distortions that are frequently found for the adiabatic excited states are examined with the aid of deformation density plots and the electron localization function (ELF).