Effects of solvation on partition and dimerization of benzoic acid in mixed solvent systems

The partition of benzoic acid between 0.1M perchloric acid solution and two kinds of mixed solvents has been carried out at 25 degrees C. The partition and dimerization constants of benzoic acid have been determined in the 1-octanol-benzene and 2-octanone-benzene systems. In both the mixed solvent systems, with increasing content of 1-octanol and 2-octanone in each mixed solvent, the partition constant of benzoic acid has been found to increase, and the dimerization constant of benzoic acid in each organic phase to decrease. These phenomena are attributable to solvation of monomeric benzoic acid by 1-octanol and 2-octanone molecules in each mixed solvent.     

Dimerization and association of an organophosphoric acid in various organic solvents

The association of bis (p-chlorophenyl) phosphoric acid with various organic solvents as well as its dimerization in these solvents was investigated. In inert solvents like kerosene, carbon tetrachloride and benzene, dimerization is very high and decreases with increasing polarity of the solvent. In polar solvents like alcohols and ketones, a strong association between HA and solvent molecules exists. The association constants were determined; the values may be regarded as a measure for the basicity of the solvents in question. The following order of the increasing basicity of the solvents was established: hydrocarbons and chlorinated hydrocarbons < ethers < ketones < alcohols.     

Synthesis of Lutein and Astaxanthin Esters and Their In Silico Activity

Russian Journal of General Chemistry - Esters of individual natural carotenoids lutein and astaxanthin with benzoic, 4-methylbenzoic, nicotinic, and mandelic acids have been synthesized. The...     

Dimerization of some substituted benzoic acids in aqueous solution from conductance measurements

Precision molar conductances of benzoic, o-toluic, 2,6-dimethylbenzoic, 2,3,6-trimethylbenzoic, and, o-fluorobenzoic acids have been determined in aqueous solution as a function of temperature and of concentration up to near saturation (<0.035 M). At the higher concentrations molar conductances are found to be less than anticipated for the simple dissociation of a 1-1 electrolyte. Although the deviations are only 1% or less they have been interpreted to show that these acids are dimerized in solution. The interpretation includes an assumption that the dimer ionizes to produce a triple ion. Increasing numbers of methyl groups lead to increasing dimerization. For those acids with two ortho groups the dimerization increases with increasing temperature while the other three show decreasing dimerization with increasing temperature. Temperature functions have been determined for the dimerization constants and from these functions standard changes in enthalpy, entropy, and heat capacity have been determined. Comparisons are made with dimerization studies in non-aqueous solvents. From these as well as the behavior of benzene in water it is concluded that a major factor driving the dimerization is hydrophobic interaction. To provide a limiting conductance of the triple ion needed in the dimerization calculations a conductance study was also made for o-Phenylbenzoic acid on the assumption that its anion provides an approximate model of the triple ion.     

Dimerization and protonation reactions of nitrosonitrobenzenes radical anions

The electrochemical behavior of 2-, 3-, and 4-nitrosonitrobenzenes (NNB) in DMF (with Bu₄NClO₄ suppoting salt) in the presence and in the absence of different proton donors (water, phenol, benzoic, acetic, chloroacetic, and sulfuric acids) is studied by the methods of cyclic voltammetry, chronoamperometry and also by electrolysis at the controlled potential. The electrochemical reduction of these compounds is shown to preferentially afford either monomeric (N-nitrophenylhydroxylamines) or dimeric (azoxy compounds) products, which is determined by the interplay between reactions of protonation and dimerization of NNB radical anions. The dimerization reactions proceed fast and reversibly to afford the corresponding dimeric dianions with the basicity much higher as compared with NNB radical anions as the result of which the monomeric products are formed in the presence of “strong” proton donors and the dimeric products form in the presence of “weak” proton donors. Like the effective rate of formation of dimeric products, the basicity of radical anions increases in the row 4- < 3- < 2-NNB.     

Distribution of carboxylic acids between water and nonpolar organic solvents

Equations which describe the distribution of carboxylic acids between water and nonpolar organic solvents, and which make allowance for their dimerization in the organic solvent, their association with water molecules, and the nonideal nature of the organic phase, have been examined. It has been shown that it is necessary to study the distribution of the carboxylic acid and water between the phases in order to determine the constants for the distribution, hydration, and dimerization of the carboxylic acids.     

苯甲酸稀溶液的萃取特性

磷酸三丁酯;正辛醇;苯甲酸稀溶液的萃取特性     

PHOTOOXYGENATION OF BIPHENYL AND ITS DERIVATIVES via PHOTOINDUCED ELECTRON TRANSFER: EFFECT OF Mg(CIO4)2 ON PHOTOOXYGENATION

The 9,10-dicyanoanthracene (DCA)-sensitized photooxygenation of biphenyl derivatives in the presence of Mg(CIO₄)₂ in acetonitrile produces benzoic acid and its derivatives in high yields. In the absence of Mg(CIO₄)₂, the rates for the consumption of biphenyl derivatives decrease by a factor of 0.5-0.8, compared with those in the presence of Mg(CIO₄)₂. In these cases, however, both biphenyls and DCA are oxygenated to give benzoic acids and anthraquinone, respectively, indicating that the addition of Mg(CIO₄)₂ retards the photooxygenation of DCA. With 4-methylbiphenyl, the photooxygenation proceeds efficiently without added Mg(CIO₄)₂, and benzene rings and methyl groups are competitively oxygenated to give benzoic acid, 4-methylbenzoic acid, 4-phenylbenzoic acid, and 4-phenylbenzaldehyde. The addition of Mg(CIO₄)₂ facilitates the oxidation of benzene rings, giving benzoic acid and 4-methylbenzoic acid as major products. These photooxygenations are initiated by a one-electron transfer from biphenyls to the excited singlet DCA and proceed via the radical cations of biphenyls and the radical anion of DCA.     

Properties of thermotropic liquid crystals induced by hydrogen bonding between pyridyl-1,2,4-oxadiazole derivatives and benzoic acid, 4-chlorobenzoic acid or 4-methylbenzoic acid

Supramolecular liquid crystalline complexes have been obtained from binary mixtures of 3-(4-pyridyl)-5-(4-n-alkoxy)phenyl-1,2,4-oxadiazoles with benzoic acid, 4-chlorobenzoic acid or 4-methylbenzoic acid. Neither the oxadiazole derivatives nor the carboxylic acids are mesomorphic, but the H-bonded complexes are. Their liquid crystalline properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction.     

Ionic strength dependence of formation constants-I Protonation constants of organic and inorganic acids

The protonation constants of formic, acetic, benzoic, oxalic, phthalic, maleic, malonic, succinic, dl-malic, dl-tartaric, aminoacetic, citric, nitrilotriacetic, ethylenediaminetetra-acetic, sulphuric and orthophosphoric acids have been determined from pH measurements, in tetraethylammonium iodide solution, at various ionic strengths in the range 0.01-1.0M (for phosphoric and sulphuric acids 0.01-0.5M). For each acid the dependence of the protonation constants on ionic strength was determined and an equation, valid for all the acids studied, to describe this was derived. The use of tetraethyl-ammonium salts as background to avoid ion-pair formation is discussed.     

Conformational equilibria in formic acid and the adduct of formic acid and hexafluoroacetone, HCO2C(CF3)2OH

Low-temperature 1H and 13C NMR spectra of formic acid (1) showed separate signals for the E and Z conformations in solvents containing a hydrogen bond acceptor, dimethyl ether. The population of E-1 (6.2% in 3:1:1 CHClF2/CHCl2F/(CH3)2O) was larger than that for 13C-labeled methyl formate in the same solvent (0.2%), which indicated that the relative populations are not determined by steric effects. The free-energy difference between the E and Z conformations of 1 was 0.9 kcal/mol. In a 1:3 CD2Cl2/(CH3)2O solvent mixture, peaks for E and Z conformations were found at low temperatures by 1H and 13C NMR for both formic acid and an adduct with hexafluoroacetone, HCO2C(CF3)2OH (2). The population of E-1 in this solvent mixture was 4.3% by 13C NMR. The carbon spectrum showed two peaks in the carbonyl carbon region of nearly equal intensities at -151.6 degrees C, with E-2 (48%) absorbing downfield of the major Z-2 (52%). The large population of E-2 confirms that electron-withdrawing groups R' in RCO2R' enhance the populations of the E-isomers. The free-energy barriers for 2 of 6.24 (E-to-Z) and 6.26 kcal/mol (Z-to-E) were determined from rate constants obtained by line shape analysis at -143.2 degrees C.     

Extraction of palladium(II) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol from nitric acid solutions

Extraction of palladium(II) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol from nitric acid solutions (carbon tetrachloride as diluent, octanol as modifier) was studied. Optimal extraction conditions were found. The reagent was shown to extract efficiently metal ions in a wide range of aqueous phase acidity by coordination mechanism. Aqueous ammonia solution was proposed as stripping agent for palladium(II). Concentrational extraction constants were calculated and thermodynamic parameters of extraction were determined.     

One-pot three-component reaction for the synthesis of novel series of fully substituted 1,3,4-oxadiazole derivatives bearing pyridine moiety

(N-isocyanimino)triphenylphosphorane, 2-pyridinecarbaldehyde, and aromatic carboxylic acids (benzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-methoxybenzoic acid, 1-naphthoic acid, and 2-naphthoic acid) undergo a 1:1:1 addition reaction under mild conditions in a one-pot reaction to afford novel series of fully substituted 1,3,4-oxadiazole derivatives in good yields.     

Spectrophotometric determination of traces of water in organic solvents (oxygen-free molecules)

Spectrophotometry and potentiometry have been used to determine the self-ionization product of formic acid and the acidity constants of hydrobromic, hydrochloric, methanesulfonic, p-toluenesulfonic, sulfuric, trifluoroacetic, pieric and benzoic acids in formic acid.     

Syntheses of Key Monomers for Advanced Polymer Materials Using Cyclodextrin as Catalyst

Terephthalic acid was synthesized by the carboxylation of benzoic acid with carbon tetrachloride in aqueous sodium hydroxide solution in the presence of cyclodextrin (CyD) and copper powder as catalyst. By the use of β-CyD at the initial molar ratio to benzoic acid of 0.5, the carboxylation at 60 °C for 7 hours produced terephthalic acid in 75 mol% yield with 87% selectivity. The selective synthesis of 4,4'-biphenyldicarboxylic acid in 70 mol% yield was achieved by the carboxylation of 4-biphenylcarboxylic acid with carbon tetrachloride in the presence of β-Cyd under similar conditions. The carboxylation of 2-naphthalene carboxylic acid with carbon tetrachloride using β-Cyd under similar conditions produced 2,6-naphthalenedicarboxylic acid in 67 mol% yield with 84% selectivity. When α-CyD and γ-CyD were used in place of β-Cyd, both the yields and the selectivities of the dicarboxylic acids were markedly small. In the absence of CyD, carboxylation did not proceed. Inclusion complex formations between β-Cyd and aromatic monocarboxylic acids were indicated by the ¹H chemical shifts of the β-Cyd. The reaction mechanism was discussed on the basis of inclusion complex formation.     

Effects on the micellar solubilization of organic compounds by surfactant micelles. I. Length of carboxylic side chains in aromatic acids

The semiequilibrium dialysis method has been used to determine solubilization equilibrium constants and activity coefficients of benzoic, phenylacetic, and hydrocinnamic acids (solubilizate) in micelles of the cationic surfactant hexadecylpyridinum chloride (cetylpyridinium chloride) in 0.1M HCl aqueous solutions. Methods described previously were employed to infer the concentrations of monomeric organic solute and surfactant on both sides of the dialysis cell. Values of the apparent solubilization constant K of the neutral acids have been correlated with mole fractions of the acid in the micelle X_A, where K=X_A/[monomeric acid]. The activity coefficients of both acid and surfactant were obtained, consistent with the Gibbs-Duhem equation. The solubilization constants of all three acids are nearly the same, indicating that there is no significant effect owing to the presence of one or more methylene groups between the carboxylate and the phenyl groups of benzoic acid. The solubilization constants also decrease appreciably, and the activity coefficients of the acids increase, as the mole fraction of the acid in the micelle increases.     

Formation of a carboxyl group satellite line in the n.m.r. spectra of solid carboxylic acids

The structural factors resulting in the formation of the carboxyl group satellite line on the low field side of the ¹H n.m.r. spectra of carboxylic acids in the solid state have been determined from the temperature dependences of the carboxyl proton chemical shifts of acetic, dimethylacetic, ethylacetic, phenylacetic, benzoic, o-methylbenzoic, p-methylbenzoic and adamantyl carboxylic acids. The carboxyl group low field satellite forms at temperatures near the melting point only in the case of carboxylic acids with bulky hydrocarbon radicals (o-methylbenzoic and adamantyl carboxylic acids).     

The Henry's law constants of water in the binary mixtures of benzene,carbon tetrachloride,and cyclohexane at 25°C

The solubilities of water in each of the three binary mixtures benzene-carbon tetrachloride, benzene-cyclohexane, and carbon tetrachloride-cyclohexane were determined as a function of solvent composition at 25°C. It was found that, as with the pure solvents, water in the 0.50 mole fraction binary mixtures of these solvents obeyed Henry's law up to saturation. The experimentally determined solubilities were converted to Henry's law constants of water for the entire range of solvent compositions. These values for the Henry's law constants were compared with theoretically calculated values. The comparisons indicated that water in the benzene-cyclohexane and in the benzene-carbon tetrachloride mixtures was preferentially solvated by benzene. Preferential solvation of water was not indicated for the carbon tetrachloride-cyclohexane mixtures.     

Synthesis of Zeaxanthin Esters

Six new zexanthin esters with 4-methylbenzoic, phenylglycolic, 2-hydroxybenzoic (salicylic), and nicotinic acids, ibuprofen, and ketoprofen, as well as benzoic acid ester, have been synthesized in anhydrous medium at 40°C in the presence of biocatalysts, Amano Lipase PS and Novozyme 435.