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.     

Solvent effects on the infrared spectra of thionyl and seleninyl chlorides

Infrared spectra of thionyl and seleninyl chlorides are reported and discussed. Complete assignment for both molecules is given on the basis of C_s symmetry. Solvent effects on XO bond (X = S, Se) have been studied in comparison with CO bond for carbonyl compounds and by means of the Kirkwood, Bauer and Magat relationship. Acceptor properties of oxychlorides for pyridinic adducts are shown.     

Charge-transfer complexes in organic chemistry—XII : Solvent effects on charge-transfer spectra

The charge-transfer transition energies of 2,6-dimethoxynaphthalene and 9-methylanthracene with tetrachlorophthalic anhydride, and acenaphthene and anthracene with 3,5-dinitrophthalic anhydride were measured in sixty aprotic solvents. The observed effects can be interpreted in terms of various solvent parameters if the solvents are divided into the following classes: halogen-containing, aromatic and n-donor solvents.     

Solvent effects on chemical processes. 3. Surface tension of binary aqueous organic solvents

The surface tension of binary solvents is modelled by analogy to solvation effects arising from solvent-solute interactions. Competitive exchange equilibria are postulated between solvent component I (water) and solvent component 2 (organic cosolvent) for solute, which in this case is air; the solvation shell is thus the surface phase. A quantitative relationship is given between surface tension and mole fractions x₁ and x₂, the model parameters being exchange equilibrium constants K₁ and K₂. The equation is analyzed, it is applied to literature surface tension data, and it is compared with an earlier model from this laboratory. Curve-fits are very good, and the parameters appear to possess physical significance.     

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.     

Solvent effects on the NMR spectra of heterocyclics

The NMR spectra of pyridine, pyrazine and imidazole are examined in acetone-d₆. The differential shifts of the ring protons are accounted for in terms of an interaction between the lone pair on the ring nitrogen atom and the carbonyl group of acetone.     

Solvent effects in the reaction of lucigenin with basic hydrogen peroxide: Chemiluminescence spectra in mixed polar solvents

Summary The chemiluminescent reaction of lucigenin with basic hydrogen peroxide has been studied in several mixtures of water with the cosolvents methanol, ethanol, 1-propanol, dimethylformamide, and dimethylsulfoxide. The chemiluminescence spectra depend on the cosolvent and its concentration in the reaction medium. With increasing cosolvent concentration, the chemiluminescence shifts to lower wavelengths. For similar cosolvents, the size of this shift increases with decreasing dielectric constant. In high-cosolvent-concentration mixtures, the chemiluminescence matches the fluorescent emission of N-methylacridone. Chemiluminescence from low-cosolvent-concentration mixtures is explained as the sum of the lucigenin and N-methylacridone fluorescent emissions, the lucigenin emission probably being a consequence of energy transfer from N-methyl-acridone. The cosolvent inhibits this energy transfer. These observations, taken together with our previous kinetic results, indicate that the reaction mechanism is the same in all the studied reaction media.

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Lösungsmitteleffekte bei der Reaktion von Lucigenin mit basischem Hydrogenperoxid: Chemilumineszenzspektren in gemischten polaren Lösungsmitteln

Zusammenfassung Die Chemilumineszenzreaktion von Lucigenin mit basischem Hydrogenperoxid wurde in verschiedenen Mischungen von Wasser mit Methanol, Ethanol, 1-Propanol, Dimethylformamid oder Dimethylsulfoxyd untersucht. Die Chemilumineszenzspektren hängen vom organischen Kosolvens und dessen Konzentration im Reaktionsmedium ab. Mit ansteigender Konzentration ergeben sich in der Chemilumineszenz Verschiebungen zu größeren Wellenlängen. Für ähnliche Kosolventien steigt diese Verschiebung mit kleineren Dielektrizitätskonstanten an. Bei hohen Kosolvenskonzentrationen gleicht die Chemilumineszenz der Fluoreszenzemission von N-Methylacridon. Die Chemilumineszenz bei kleinen Kosolvenskonzentrationen kann als die Summe der Fluoreszenzemission von Lucigenin und N-Methylacridon erklärt werden, wobei die Lucigeninemission vermutlich eine Folge eines Energietransfers von N-Methylacridon ist. Das Kosolvens verhindert diesen Energietransfer. Diese Beobachtungen, zusammen mit früheren kinetischen Resultaten, erlauben den Schluß, daß der Reaktionsmechanismus in allen Reaktionsmedien der gleiche ist.

     

Solvent effects on the infrared spectra of beta-alkoxyvinyl methyl ketones I. Carbonyl and vinyl stretching vibrations

Infrared spectroscopy studies of six beta-alkoxyvinyl methyl ketones, with common structure R(1)O-CR(2)CH-COR(3), where R(1)=R(3)=CH(3), R(2)=H (1); R(1)=C(2)H(5), R(2)=H (2); R(3)=CF(3); R(1)=R(2)=CH(3), R(3)=CF(3) (3); R(1)=C(2)H(5), R(2)=C(6)H(5), R(3)=CF(3) (4); R(1)=C(2)H(5), R(2)=4-O(2)NC(6)H(4), R(3)=CF(3) (5); R(1)=C(2)H(5), R(2)=C(CH(3))(3), R(3)=CF(3) (6) in 11 pure organic solvents of different polarity were undertaken to investigate the solute-solvent interactions and to correlate solvent properties by means of linear solvation energy relationships (LSER) with the carbonyl and vinyl stretching vibrations of existing stereoisomeric forms. It was shown that contrary to simple carbonyl-containing compounds where solvent HBD acidity (alpha) has the largest influence on the nu (CO) band shift to lower wavenumbers, the dipolarity/polarizability (pi) term plays the main role in the interactions of conjugated enones with solvent molecules leading to the nu (CO) and nu (CC) bathochromic band shifts. The trifluoroacetyl group possesses a reduced ability to form hydrogen bonds with solvents. For the nu (CC) band of non-fluorinated enone 1 solvent HBD acidity (alpha) and solvent HBA basicity term (beta) play a perceptible role, whereas for 2 these terms are not significant. beta-Substituents in fluorinated enones such as R(2)=H, C(6)H(5), and C(CH(3))(3) assist in the intermolecular hydrogen bond formation of the carbonyl moiety with HBD solvents, while beta-substituents such as CH(3) and 4-NO(2)C(6)H(4) prevent the CO group to form the H-bonds with HBD solvents (the solvent HBD acidity term (alpha) is not significant). The comparison of four conformers of the enone 1 reveals that (EEE) form is the most polarizable conformer; the influences of the solvent dipolarity/polarizability (pi) and solvent HBD acidity (alpha) term on the bathochromic nu (CO) band shift are opposite to one another.     

Solvent effects on the absorption spectra of merocyanine dyes

Solvent effects on the lowest-energy electronic transitions of two merocyanines derived from quinoline have been studied using nine different solvent parameters reported in the literature. Relative merits and deficiencies of different parameters have been assessed. From the correlation results, attempts have been made to propose a solute-solvent interaction mechanism. For an assorted set of 19 solvents, as well as for a set of nine hydroxylic solvents, excellent results are obtained with correlation equation involving E_T(30) and Hilderbrand's solubility parameter _H.     

Solvent effects in NMR spectra induced by aromatic solvents in 1,4-dioxanes, 1,3-dioxolanes and in sulphur analogues

NMR solvent effects induced by aromatic solvents on some 1,4-dioxanes, 1,3-dioxolanes and on some sulphur analogue derivatives are reported. The shielding effect of the aromatic solvents is examined in respect to the structure of the solute.     

Solvent effects on acid-base behavior: Five uncharged acids in water-sulfolane solvents

An electrometric titration method utilizing glass electrodes and silver-silver bromide electrodes in a cell without liquid junction has been applied to a determination of the dissociation constants of five uncharged weak acids (HA) in four mixtures of water and sulfolane (tetramethylene sulfone) at 25°C. The acids studied were monochloroacetic, formic, benzoic, and acetic acids andp-nitrophenol, and the mole fractions (x ₂) of sulfolane in the mixed solvents were 0.2, 0.4, 0.6, and 0.8. All measurements were made at a constant ionic strength of 0.02 mole-kg^–1 in a solution containing NaBr at a molality of 0.01 mole-kg^–1. The cell was standardized by measurements of HClO₄ at molalities from 0.002 to 0.01 mole-kg^–1 and, in subsequent measurements, a solution of NaA was titrated with HClO₄. To obtain the thermodynamic pK, an activity correction derived from the Debye-Hückel theory was applied. The pK of all five acids was found to vary linearly withx ₂ in the range 0 to 0.8. By comparison of data for acetic acid in water-methanol, water-dioxane, and water-sulfolane solvents, it was shown that the results are consistent with the known properties of sulfolane (low acidity, basicity, and solvating power), but the linear variation of pK with solvent composition remains unexplained.On leave 1973–1975 from the University of Gdansk, Poland.     

Effect of polar solvents on νpo in infrared spectra and chemical shifts in31p NMR spectra of phosphoryl compounds

Conclusions We measured the _po frequencies in the IR spectra of two phosphoryl compounds in a number of dipole solvents and found that a linear relation exists between the _po shifts and the changes in ³¹P chemical shifts of triethylphosphine oxide in the corresponding solvents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1191–1193, May, 1977.     

Solvent effects on electronic spectra studied by multiconfigurational perturbation theory

The complete active space (CAS) self-consistent field (SCF) method combined with multiconfigurational second-order perturbation theory (CASPT2) and a self-consistent reaction field (SCRF) model is used to study the effect of solvation on excited states of different molecules such as acetone, pyrimidine, some aminobenzene derivatives, indole, and imidazole. The present SCRF model, in which the solute molecule is placed into a spherical cavity surrounded by a dielectric continuum, also includes a repulsive potential representing the solute–solvent exchange repulsion and considers the time dependence of the absorption process. In general, we find that our calculations do reproduce the trends observed in experiment but underestimate the solvatochromic shifts. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65 : 167–181, 1997     

Solvent extraction of thorium(IV) with dibutyldithiophosphoric acid in various organic solvents

The extraction of thorium(IV) from perchlorate solutions with di-n-butyldithiophosphoric acid (HBudtp) in various organic solvents occurs through an ion exchange mechanism. The extracted species in the organic phase is an eight-coordinate complex Th(Budtp)₄. The higher values of the distribution ratio obtained in HBudtp-benzene-water system than in HBudtp-n-butanol-water system are explained by higher solubility of the complex species in nonpolar solvents. The position of the extraction curves in the pH-range lower than 0.7 reduces the complexation of thorium(IV) with Budtp^– in the aqueous phase and also the hydrolysis process.     

Solvent effects on the structure of N-methylpyrrole as studied by nmr in nematic solvents

The proton NMR spectra of N-methylpyrrole oriented in the nematic phases of liquid crystals with positive and negative diamagnetic anisotropies and their mixtures are reported. Geometrical parameters derived from the spectra at the critical point in the mixture of liquid crystals with positive and negative diamagnetic anisotropies, where macroscopic diamagnetic anisotropy vanishes, are similar to those obtained in the solvent with negative diamagnetic anisotropy. However, significant distortions in the molecular structure attributed to solvent effects have been observed in liquid crystals with positive diamagnetic anisotropy. The minimum energy conformation has one CH of the methyl perpendicular to the ring.