•ν(CO) of VAc is employed to reflect chemical reactivity of CC group in VAc.•Correlations between the νcal(CO) and solvent parameter equations suggest limitation of using the PCM model.•Long-range electrostatic solvation free energies of VAc are calculated by the SMD model.•Ab initio calculation allow assignments of the νexp(CO) in alcohol solvents.The infrared vibration frequencies of vinyl acetate (VAc) in 18 different solvents were theoretically computed at Density Function Theory (DFT) B3LYP/6-311G* level based on Polarizable Continuum Model (PCM) and experimentally recorded by FT-IR spectroscopy. The solvent-induced long-range bulk electrostatic solvation free energies of VAc (ΔGelec) were calculated by the SMD model. The CO stretching vibration frequencies of VAc were utilized as a measure of the chemical reactivities of the CC group in VAc. The calculated and experimental CO stretching vibration frequencies of VAc (νcal(CO) and νexp(CO)) were correlated with empirical solvent parameters including the KBM equation, the Swain equation and the linear solvation energy relationships (LSER). Through ab initio calculation, assignments of the two CO absorption bands of VAc in alcohol solvents were achieved. The PCM, SMD and ab initio calculation offered supporting evidence to explain the FT-IR experimental observations from differing aspects.Graphical abstract

FT-IR spectra of benzaldehyde in 11 different organic solvents were recorded and analyzed. The density functional theory (DFT) B3LYP/6-31G* method was chosen to calculate the infrared spectrum of benzaldehyde in gaseous state. The electrostatic effects of different solvents in benzaldehyde solutions were calculated using DFT with the self-consistent isodensity polarizable continuum model (SCI-PCM). Two remarkable carbonyl (CO) peaks of benzaldehyde were observed by FT-IR in alcohol solvents, which were caused by different hydrogen bond species and explained by ab initio calculation. The results showed that the combination of SCI-PCM model and ab initio calculation could give excellent agreements with FT-IR spectra of title compound in solutions.Graphical abstractHighlights► B3LYP/6-31G* is the optimum method and basic set to calculate νCO of benzaldehyde. ► SCI-PCM model and parameter G describe non-specific interaction in solutions. ► Ab initio calculations simulate the hydrogen bonds in alcohol solution. ► This method provides a new way to study solvent effects.

The studies on the solvent effects of methyltestorone (MT) in 19 different organic solvents and n-C6H14/CHCl3 binary solvents were undertaken by FTIR spectroscopy. The wavenumbers of carbonyl stretching vibration for MT (ν(CO)) in individual solvents were correlated with the empirical solvent parameters such as Schleyer's linear free energy equation (G-value), the solvent acceptor number (AN) and the linear solvation energy relationships (LSER), respectively. The solvent-induced carbonyl stretching vibration wavenumber shifts of MT exhibited a better correlation with the LSER than the other solvent parameters. With the increase of the volume fraction of chloroform (XCHCl3) in the n-C6H14/CHCl3 binary solvents, two kinds of ν(CO) of MT were observed and assigned. The formation constant (K0) of the interaction between MT and CHCl3 and the free energy change (ΔG0) of the system were calculated in the binary solvents by Nash's method.

The infrared absorption spectra of the carbonyl stretching vibrations of 6-methylcoumarin (6MC) have been investigated in CCl4/ROH mixtures (CCl4/C2H5OH, CCl4/n-C3H7OH, CCl4/i-C3H7OH, and CCl4/t-C5H11OH). Two types of carbonyl stretching vibration bands for 6MC are found with the change of the mole fraction of the aprotic solvent CCl4(XCCl4)CCl4(XCCl4) in binary solvent mixtures. The dependencies of the frequencies of carbonyl stretching vibrations υ(CO) on XCCl4XCCl4 allow a distinction and assignment of all species resulting from the solvent–solute interactions. Linear correlations between the υ(CO) of each species and XCCl4XCCl4 are found. The influence on the transformation of some species caused by the self-associated alcohols is discussed.

The infrared absorption spectra of the androsterone in 19 pure organic solvents have been investigated. The carbonyl stretching vibration frequencies of androsterone observed in the solvents were correlated with the empirical parameters G, Swain parameters (Aj and Bj) and the linear solvation energy relationships (LSER). The applicabilities of different parameters were discussed and the solute–solvent interactions in single solvents were studied in detail. The correlation results indicated that the LSER is optimal for a complete description of solute–solvent interactions while G-values and Swain parameters are unilateral.

The infrared spectroscopy studies of the C3 and C20 carbonyl stretching vibrations (υ(CO)) of progesterone in CHCl3/cyclo-C6H12 binary solvent systems were undertaken to investigate the solute–solvent interactions. With the mole fraction of CHC13 in the binary solvent mixtures increase, three types of C3 and C20 carbonyl stretching vibration band of progesterone are observed, respectively. The assignments of υ(CO) of progesterone are discussed in detail. In the CHCl3-rich binary solvent systems or pure CHCl3 solvent, two kinds of solute–solvent hydrogen bonding interactions coexist for C20 CO. Comparisons are drawn for the solvent sensitivities of υ(CO) for acetophenone and 5α-androstan-3,17-dione, respectively.