Solvent effects on infrared spectra of 5-methyl-7-methoxy-iso-flavone in single solvent systems

Synthesis of 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione and solvent effects on their infrared spectra in organic solvents

In the present study novel 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one (compound (4)) and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione (compound (5)) were synthesized. These oxadiazole ring derivatives were characterized by IR, ¹H NMR, ¹³C NMR and HRMS analyses. The solvent effects on CO, CN and CS stretching vibrational frequencies (ν(CO), ν(CN) and ν(CS)) of synthesized compounds were investigated experimentally using attenuated total reflection (ATR) infrared spectroscopy and compared with the theoretical results assigned using the potential energy distribution (PED) contributions. Furthermore, the ν(CO), ν(CN) and ν(CS) of compound (4) and compound (5) were correlated with empirical solvent parameters such as the solvent acceptor numbers, the Swain equation, the Kirkwood-Bauer-Magat equation, and the linear solvation energy relationships. Apart from the linear effects investigated in similar studies, solvent-induced vibrational shifts were investigated using the quadratic equation. The prediction capabilities of empirical solvent parameters were statistically compared. It was found that the linear solvation energy relationships show better correlation than the other empirical solvent parameters. Additionally, the quadratic equation provided more accurate predictions for the vibrational frequency locations than the Swain and the linear solvation energy relationships equations.

FT-IR spectroscopy combined with DFT calculation to explore solvent effects of vinyl acetate

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 C=O stretching vibration frequencies of VAc were utilized as a measure of the chemical reactivities of the CC group in VAc. The calculated and experimental C=O stretching vibration frequencies of VAc (νcal(C=O) and νexp(C=O)) 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 C=O 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.

Study of the solvent effects on the molecular structure and CO stretching vibrations of flurbiprofen

The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.

FT-IR study on interactions between medroxyprogesterone acetate and solvent in CHCl₃/cyclo-C6H₁₂ and CCl₄/cyclo-C6H₁₂ binary solvent systems

The intermolecular interactions between medroxyprogesterone acetate (MPA) and CHCl(3) and CCl(4) solvent in CHCl(3)/cyclo-C(6)H(12) and CCl(4)/cyclo-C(6)H(12) binary solvent systems have been studied by Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that there are hydrogen bonding interactions between oxygen atoms of all carbonyl groups in MPA and hydrogen atom of CHCl(3) so as to form 1:3 complex of MPA with CHCl(3) and produce three new absorption bands at 1728.9-1736.1, 1712.7-1717.4 and 1661.9-1673.8 cm(-1), respectively. And, 1:1 complex of MPA with CCl(4) is formed in CCl(4)/cyclo-C(6)H(12) binary solvent as a result of hydrogen bonding interaction between C3 carbonyl group and empty d-orbital in chlorine atom of CCl(4) leading to producing new absorption band at 1673.2-1674.2 cm(-1). However, all free carbonyl and associated carbonyl stretching vibrations of MPA in CHCl(3)/cyclo-C(6)H(12) and CCl(4)/cyclo-C(6)H(12) binary solvent systems shift to lower wavenumbers with the increasing of volume fraction of CHCl(3) and CCl(4) in binary solvent systems owing to the dipole-dipole interaction and the dipole-induced dipole interaction between MPA and solvents.

FT-IR spectroscopy and DFT calculation study on the solvent effects of benzaldehyde in organic solvents

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 (C=O) 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.

FTIR Study of Molecular Interaction in Butyl Methacrylate–Organic Solvents Mixtures

FTIR spectroscopic study of butyl methacrylate (BMA) in different pure organic solvents were undertaken to investigate the solute–solvent interactions. The frequency of carbonyl stretching vibration ν(C=O) of BMA is correlated with the solvent properties such as the KBM parameter, the solvent acceptor number (AN), and the linear salvation energy relationships (LSER). The solvent-induced stretching vibration frequency shifts showed a better correlation with LSER parameters than AN. While no linear correlation between dielectric constants and the frequencies showed that the KBM relationship was unsuitable for this molecule. Also the solvent effect on the strength of hydrogen bond formation between free OH group of 1-butanol and C=O group of BMA is discussed in terms of local specific interaction between the solute and solvent.

FTIR spectral studies of methyltestorone in single and binary solvent systems

The studies on the solvent effects of methyltestorone (MT) in 19 different organic solvents and n-C(6)H(14)/CHCl(3) binary solvents were undertaken by FTIR spectroscopy. The wavenumbers of carbonyl stretching vibration for MT (nu(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 (X(CHCl3)) in the n-C(6)H(14)/CHCl(3) binary solvents, two kinds of nu(CO) of MT were observed and assigned. The formation constant (K(0)) of the interaction between MT and CHCl(3) and the free energy change (DeltaG(0)) of the system were calculated in the binary solvents by Nash's method.

Solvent effects on infrared spectra of progesterone in CHCl3/cyclo-C6H12 binary solvent systems

The infrared spectroscopy studies of the C3 and C20 carbonyl stretching vibrations (upsilon(C=O)) 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 upsilon(C=O) 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 C=O. Comparisons are drawn for the solvent sensitivities of upsilon(C=O) for acetophenone and 5alpha-androstan-3,17-dione, respectively.

New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 2. Assessment of cooperativity effects

Solvent effects on O-H stretching vibration frequency of methanol in hydrogen bond complexes with different bases, CH3OH...B, have been investigated by FTIR spectroscopy. Using chloroform as a solvent results in strengthening of CH3OH...B hydrogen bonding due to cooperativity between CH3OH...B and Cl3CH...CH3OH bonds. A method is proposed for quantifying the hydrogen bond cooperativity effect. The determined cooperativity factors take into account all specific interactions of the solute in proton-donor solvents. In addition, a method of estimation of cooperativity factors Ab and AOX in system (CH3OH)2...B is proposed. It is demonstrated that in such systems, the cooperativity factor of the OH...B bond decreases and that of the OH...O bond increases with increasing the acceptor strength of the base B. The obtained results are in a good agreement with the data obtained previously from matrix-isolation FTIR spectroscopy.

New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 1. Assessment of van der Waals interactions

Solvent effects on OH stretching vibrations in several complexes with hydrogen bonding have been investigated by FTIR spectroscopy. To assess the influence of van der Waals (vdW) interactions on frequency shifts, a new parameter of solvent, square root deltacavhS, is proposed. This parameter has been derived from equations describing enthalpy of non-specific solvation. Linear correlation was established between the OH frequency shift (with respect to the gas phase) and parameter square root deltacavhS for a series of complexes of aliphatic alcohols with standard proton acceptors. Linear correlations with square root deltacavhS were also observed for a series of "free" O-H and also C=O, P=O, S=O and C-Br stretching vibrations. A new method is proposed for estimating the gas-phase stretching frequency from IR spectra of solutions. In addition, frequencies of "free" X-H groups in neat bases were deduced from the experimental data.

Molecular Interpretation for the Solvation of Poly(acrylamide)s. I. Solvent-Dependent Changes in the CO Stretching Band Region of Poly(N,N-dialkylacrylamide)s

The solvation of poly(N,N-dimethylacrylamide) (PNdMA) and poly(N,N-diethylacrylamide) (PNdEA) in various protic and aprotic solvents has been studied by using infrared (IR) spectroscopy. Because PNdMA and PNdEA have the same polar functional group, their IR spectra show quite similar solvent effects. Unexpectedly, the solvent-dependent changes of the C=O stretching vibration (nu(C=O)) bands of the two polymers cannot be explained only by dielectric constants of the solvents. Then, infrared spectra of N,N-dimethylacetamide (NdMA) and N,N-diethylacetamide (NdEA), monomer models for PNdMA and PNdEA, respectively, in the same solvents as the polymer solutions have also been examined. Interestingly, the solvent-dependent spectra in the nu(C=O) band region of NdMA and NdEA are correlated with those of PNdMA and PNdEA, respectively, except for slight deviations, which may be ascribed to molecular mobility and/or exclusive volume. These correlations permit one to regard the solvation of the polymers as that of the corresponding monomers. As a result, we have proposed the assignments of nu(C=O) bands for the PNdMA and PNdEA solutions regarding the interactions between solvents and NdMA and NdEA as hydrogen bondings. In the IR spectra of PNdMA and PNdEA in the protic solvents, two C=O bands are mainly observed; one appears at a similar frequency to that of a C=O band observed for the monomer solution, and the other is characteristic of the polymer systems. The former band is likely to reflect the solvation behavior of PNdMA and PNdEA. The results clearly show that the solvation of a polymer can be interpreted at the molecular level using infrared spectroscopy sensitive to solvent effects.

Solvent effects on infrared spectra of methyl 4-hydroxybenzoate in pure organic solvents and in ethanol/CCl4 binary solvents

Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents.

Infrared study on solvent-solute interactions of 2-acetylthiophene in binary mixtures

The infrared absorption spectra of the carbonyl stretching vibrations of 2-acetylthiophene (AcTh) have been investigated in cyclo-hexane/alcohol mixtures (C6(12/C2H5OH; (6H12/n-C4H9OH; C6H12/i-C3H7OH and C6H12/t-C5H11OH). Five types of carbonyl stretching vibration bands for AcTh are found with the change of the mole fraction of the aprotic solvent C6H12 (x(C6H12)) in binary solvent mixtures. The dependencies of the frequencies of carbonyl stretching vibrations (nu(C=O)) on x(C6H12) allow a distinction and assignment of all species resulting from the solvent-solute interactions. Linear correlations between the nu(C=O) of each species and x(C6H12) are found. The influence on the transformation of some species caused by the self association of alcohols is discussed.

Solvent effects on infrared spectra of 2-acetylthiophene in organic solvents

Infrared spectroscopy studies of 2-acetylthiophene (ACTH) in 18 different organic solvents, both polar and non-polar, were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration upsilon(C=O) of ACTH were correlated with the properties such as the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The solvent-induced stretching vibration frequency shifts showed a better correlation with the LSER than the AN. A six-membered ring-like hydrogen bonding structure was presented and the solvent effects of ACTH in alcohol solvents were investigated in detail.