Aqueous Solutions Of 2-propanol Research Articles

SOLVENT AND SUBSTITUENT NATURE EFFECT ON THE 2-NITROAZOBENZENES HYDROGENATION SELECTIVITY ON SKELETAL NICKEL

The elucidation of the reasons and character of the influence of nature substituent and solvent composition on the kinetic features and selectivity of liquid-phase catalytic hydrogenation of compounds containing several reactive capable groups is a theoretical and practically significant task. In the presented work the process of 2-nitroazobenzene derivatives hydrogenation with various substituents was investigated in order to obtain the corresponding benzotriazoles on a skeletal nickel catalyst in a neutral azeotropic aqueous solution of 2-propanol, and in the presence of acetic acid or sodium hydroxide. According to the data obtained, the solvent composition has a decisive influence on the selectivity of this process. The transformation of azo- and nitro groups, included in the initial compound, proceeds in parallel stages, and the introduction of acidic or basic additives leads to а change in the rate ratio of these stages. Appropriately, selectivity of 2-nitroazobenzene derivatives hydrogenation changes with respect to reaction products containing a triazole ring, in particular, with respect to N-oxides of substituted benzotriazoles, and also with respect to nitrohydrazo compounds. The greatest influence of substituent nature on the hydrogenation selectivity in a solvent with any composition is manifested for the group whose transformation rate in a given medium is higher. In the presence of acid the substituent variation is more strongly reflected in the hydrogenation rate of azo group, and in the basic medium – of nitro group. It was found that the change in the transformation rate of both reactive capable groups corresponds to the Hammett constant alteration. The electron acceptor substituent has a deactivating effect on the transformation rate of nitro as well azo group. To increase the selectivity of substituted 2-nitroazobenzenes hydrogenation with respect to compounds containing a triazole ring, it is recommended to introduce a base into the aqueous solution of 2-propanol.

Physical properties of aqueous solutions of 1-propanol near its pequliar point

The work is devoted do the investigation of ultrasound absorption in aqueous solutions of 1- and 2-propanols near their peculiar points. It is assumed that the anomalous ultrasound absorption is caused by the formation of unstable nuclei of a new phase. It is noted, that the concentrations xp(MLS) and xp(US), where the intensities of molecular light scattering and ultrasound absorption take their maxima respectively as well as the point where the concentration curves for differ temperatures intersect are close to each other. A theoretical model for the ultrasound absorption by a nucleus is constructed. The characteristic size of nucleus and the typical time decay for its radial vibrations are estimated. The behavior of the ultrasound absorption coefficient is analyzed on resonance frequencies (f∼10 MHz) and ones removed from them (f≫10MHz). All characteristic experimental peculiarities of the resonance and classic absorption are reproduced with satisfactory accuracy in the framework of the model proposed.

Investigation of salt effect of some inorganic salts and ionic liquids for ibuprofen in aqueous solutions of 1-propanol: volumetric, acoustic and viscometric studies

In this study, salt effect of sodium chloride, potassium chloride, choline acetate (ChAce), choline lactate (ChLac) and choline propionate (ChPro) for ibuprofen in aqueous solutions of 1-propanol were investigated using volumetric, acoustic and viscometric methods. Density, speed of sound and viscosity of quaternary systems (ibuprofen + water + 1-propanol + NaCl/KCl/ChAce/ChLac/ChPro) were measured at temperatures T = 288.15, 298.15 and 308.15 K. Limiting apparent molar volume and limiting apparent molar isentropic compressibility at infinite dilution were calculated using experimental density and speed of sound. Limiting apparent molar volume of ibuprofen increased in the presence of NaCl and KCl; whereas limiting apparent molar volume decreased in the presence of ionic liquids. Therefor NaCl and KCl have salting-out effect; whereas ChAce, ChLac and ChPro have salting-in effect. Also, molar free energy activation of solvent and solute were evaluated using viscosity data. The molar free energy activation of solute was greater than solvent; therefore ibuprofen has a maker structure nature in solvents (water + 1-propanol + NaCl/KCl/ChAce/ChLac/ChPro).

ВЛИЯНИЕ СОСТАВА РАСТВОРИТЕЛЯ НА КИНЕТИКУ ГИДРОГЕНИЗАЦИИ 4-НИТРО-2'-ГИДРОКСИ-5'-МЕТИЛАЗОБЕНЗОЛА НА СКЕЛЕТНОМ НИКЕЛЕ В ВОДНЫХ РАСТВОРАХ 2-ПРОПАНОЛА

The article is devoted to the analysis of the kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in aqueous solutions of 2-propanol without additives and with additions of acetic acid and hydroxide. Elucidation of the effect of the solvent composition on the kinetics of transformations of compounds containing several reactive groups is a theoretical and practically significant problem. According to the data obtained, during the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel, the introduction of an acid or base into an aqueous solution of 2-propanol of azeotropic composition leads to a change in the ratio of directions in the parallel-sequential scheme of transformations of the starting compound. With the introduction of acetic acid, the contribution of the direction due to the transformation of the azo group noticeably increases, while the introduction of sodium hydroxide completely suppresses this process and the addition of hydrogen in the first phase of the reaction is carried out exclusively at the nitro group in the starting 4-nitro-2'-hydroxy -5'-methylazobenzene. The change in the contributions of the directions associated with the transformation of the azo or nitro group in 4-nitro-2′-hydroxy-5′-methylazobenzene cannot be caused by a change in the excess adsorption values of the hydrogenated compound. When the adsorption values of 4-nitro-2'-hydroxy-5'-methylazobenzene change within 30%, the rate constants of hydrogenation of the starting compound under the influence of the solvent change more than 8 times. One of the reasons for such a change in the observed rate constants for the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene may be a change in the ratio of forms of hydrogen adsorbed on the catalyst surface under the influence of a solvent.

A new methodology for determining the temperature of maximum density against pressure. Application to 2-propanol and ethanol aqueous solutions

Aqueous solutions of 2-propanol and ethanol are experimentally studied in order to obtain the location of the maximum of density versus temperature at high pressure. To this aim, a new technique based on measuring the pressure against temperature for several quasi-isochores was developed. These data are combined with isothermal compressibility, experimentally obtained from high pressure density data, to determine the isobaric thermal expansivity in the quasi-isochores. The temperature of maximum density is obtained by detecting the temperature for which this magnitude becomes zero. These results are compared with those obtained using highly precise densitometry at atmospheric pressure and also with literature data. The differences between the temperature of maximum density for solutions and that of water are positive for very diluted solutions, but they become negative as concentration is raised, which constitutes a quite unusual behavior as compared with other systems. As pressure is raised, this anomalous behavior becomes much more pronounced with positive deviations that exceed 1.5 K at the highest pressures. The underlying microscopic picture that could explain the observed behavior is suggested.

Measurement and modelling solubility of amino acids and peptides in aqueous 2-propanol solutions.

Amino acids and peptides are essential components in the biochemical industry. The final products are employed in a wide range of applications and are often synthesized by fermentation and purified in a complex downstream process. One possible separation step is using an additional solvent to lower the solubility of the desired product and, thus, promote the crystallization of the particular component. Therefore, it is crucial to have accurate knowledge of the solubility of these components. In this work, the solubilities of 20 proteinogenic amino acids and 21 peptides in aqueous 2-propanol solutions were gravimetrically determined. Additionally, the pH values of the saturated liquid phases were measured and the crystal structures of solid crystals were analysed using X-ray diffraction. The anti-solvent 2-propanol caused a decrease in the solubilities of the amino acids and peptides upon increasing its mass fraction. Exceptions were found for amino acids with aromatic substituents, l-phenylalanine and l-tyrosine. The solubility of 15 amino acids and 18 peptides was successfully modelled using the equation of state PC-SAFT that used recently determined melting properties of the amino acids and peptides as input data.

On-Off of Co-non-solvency for Poly(N-vinylcaprolactam) in Alcohol-Water Mixtures: A Molecular Dynamics Study.

Poly(N-vinylcaprolactam) (PVCL) exhibits co-non-solvency in aqueous solutions of 2-propanol but not in methanol. What distinguishes the impact of these two cosolvents on the polymer conformational stability? We report a molecular dynamics simulation study on PVCL 50-mer and monomers dissolved in methanol-water and 2-propanol-water mixtures. We show that the alcohol-concentration dependence of the effective attraction between a pair of PVCL monomers closely resembles the conformational changes in a single PVCL 50-mer as well as the experimentally observed behavior for PVCL chains. We also found that, at the co-non-solvency maximum, the monomer-monomer attraction works over a long-range beyond the solvent-separated distance. Then, we correlate the long-range attraction to the appearance of a dense alcohol concentration accumulated between the monomers. Furthermore, we distinctly demonstrate that the co-non-solvency of PVCL monomers can be switched on/off by artificially tuning the alcohol size while keeping the energetic parameters. Thus, we conclude that the magnitude of the excluded volume effect in alcohol accompanying the gain in translational entropy of the solvent is crucial to the occurrence of PVCL polymer co-non-solvency.

INFLUENCE OF ADDITIVES OF ACID ON STAGE OF TRANSFORMATIONS OF 4-NITRO-2'-HYDROXY-5'-METHYLASOBENZENE ON SKELETONIC NICKEL IN WATER SOLUTION OF 2-PROPANOL

The article is devoted to the analysis of the reaction kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in an aqueous solution of 2-propanol with acetic acid addition on skeletal nickel at different initial quantity of the starting compound. Clarification of the sequence of transformations of compounds containing several reactive groups, and the development of approaches to controlling the selectivity of processes with their participation is a practically significant task. According to the data obtained, at both low and high initial concentrations the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in a 2-propanol aqueous solution-0.01 M CH3COOH solvent proceeds in two parallel directions. The largest contribution in the first phase of the reaction is made by the azo group conversion of the starting compound, in contrast to the reaction in an aqueous solution of 2-propanol without acid addition. An increase in the initial quantity of the hydrogenated compound above its solubility limit leads to an increase in the rate of conversion of the azo group in 4-nitro- and 2-amino-2'-hydroxy-5'-methylazobenzene. Consequently, optimum quantity of 4-nitroaniline and 2-amino-2'-hydroxy-5'-methylazobenzene in the bulk solution during hydrogenation of the specified quantity of 4-nitro-2'-hydroxy-5'-methylazobenzene practically didn’t change, in contradiction to the hydrogenation on skeletal nickel in a neutral aqueous solution of 2-propanol. In a neutral aqueous solution of 2-propanol, when passing to high concentrations of the hydrogenated compound, the maximum yield of 4-nitroaniline increases twice as long the better, while as 4-amino-2'-hydroxy-5'-methylazobenzene, is reduced conversely. The results obtained do not contradict the concept of a parallel-sequential scheme for the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene. One of the directions involves the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene through 4-nitroaniline and 2-amino-4-methylphenol due to the hydrogenation of the azo group, and the second is the conversion of 4-nitro-2'-hydroxy-5'- methylazobenzene via 4-amino-2'-hydroxy-5'-methylazobenzene by reduction of the nitro group. At the end of the reaction, all the intermediate compounds are reduced to 2-amino-4-methylphenol and 1,4-phenylenediamine. When acetic acid is introduced into the composition of the neutral solvent 2-propanol-water, the contribution of the direction that ensures the formation of 4-nitroaniline and 2-amino-4-methylphenol to the overall reaction rate increases. An increase in the initial amount of 4-nitro-2′-hydroxy-5′-methyl-azobenzene leads to an increase in the rate of conversion of the azo group in the starting compound and to a decrease in the rate of conversion of 4-amino-2′-hydroxy-5′-methylazobenzene. The effect of the acid on the change in the conversion rates of nitro and azo groups to 4-nitro-2′-hydroxy-5′-methylazobenzene does not contradict the previously obtained results for the hydrogenation of its analogue, 2-nitro-2′-hydroxy-5-methylazobenzene, as well as individual compounds containing a nitro and azo group.

HYDROGEN ROLE IN SELECTIVITY OF SUBSTITUTED NITRO-AZOBENENES HYDROGENI-ZATION ON SKELETAL NICKEL IN 2-PROPANOL AQUEOUS SOLUTIONS

Elucidation of the substituted nitrobenzenes transformations sequence, in particular, containing several reactive groups and the development of approaches to the control of the selectivity of processes involving them is of interest from both theoretical and practical points of view. The article is devoted to the analysis of the hydrogenation kinetics of 2-nitro-2'-hydroxy-5'-methylazobenzene, 4-nitro-2'-hydroxy-5'-methyl-isobenzene, 4-nitroaniline, 4-amino-2'-hydroxy-5'-methylazobenzene on skeletal nickel in 2-propanol aqueous solutions of different composition, including with the addition of acetic acid or sodium hydroxide with various initial amounts of organic compound. The rise in the 4-nitro-2'-hydroxy-5'-methylazobenzene initial amount leads to increase in the nitro group transformation rate in the starting compound and to decrease in the azo-group transformation rate. The effect of sodium hydroxide additives in the 2-propanol aqueous solution on the nitro- and azo-groups conversion rate into 4-nitro-2'-hydroxy-5'-methyl-isobenzene is analogous to the change in the individual compounds hydrogenation rates (4-nitroaniline and 4-amino-2'-hydroxy-5'-methylazobenzene). Obtained results do not contradict the parallel-sequential scheme concept for the 4-nitro-2'-hydroxy-5'-methylazobenzene transformations. One of the directions is associated with the azo-group transformation into 4-nitro-2'-hydroxy-5'-methylazobenzene and 4-nitroaniline and 2-amino-4-methylphenol formation, and the second with the 4-nitro-2'-hydroxy-5'-methyl-isobenzene conversion through 4-amino-2'-hydroxy-5'-methyl-isobenzene by the nitro-group reducing. At the reaction end, all intermediate compounds are reduced to 2-amino-4-methylphenol and 1,4-phenylenediamine. When 2-nitro-2'-hydroxy-5'-methylazobenzene is hydrogenated, one of the directions leads to the 2-nitro-2'-hydroxy-5'-methylhydrazobenzene formation, and the second to the product containing the triazole cycle - N-oxide 2-2'-hydroxy-5'-methylphenylbenzotriazole. At the reaction end, these compounds are reduced to 2-2'-hydroxy-5'-methylphenylbenzotriazole and 2-amino-4-methylphenol and 1,2-phenylenediamine, respectively. In the solution at the sodium hydroxide presence, 2-nitro-2'-hydroxy-5'-methylhydrazobenzene transforms into the N-oxide 2-2'-hydroxy-5'-methylphenylbenzotriazole as a result of intramolecular rearrangement.

Hydrogenation of Substituted Benzenes Containing Nitro and Azo Groups over Skeletal Nickel in Aqueous Solutions of 2-Propanol

An analysis is made of the kinetic characteristics of the hydrogenation of 4-nitro- and 2-nitro-2'-hydroxy-5'-methylazobenzenes, 4-nitroaniline and 4-aminoazobenzene over skeletal nickel in neutral azeotropic 2-propanol–water mixture and in the same solvent in the presence of acetic acid or sodium hydroxide. It is found that the selectivity of the hydrogenation of these isomers to the intermediate products depends on the composition and nature of the solvent, and is determined by the rate of reactive group conversion. Compared to the process in the presence of sodium hydroxide, which suppresses the route leading to the predominant hydrogenation of the nitro group, the contribution from the transformation of azo group is considerably greater in the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of acetic acid. Adding a base to the solvent during the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene accelerates the rate of nitro group conversion and the intramolecular cyclization of the intermediate compound, increasing the selectivity towards the products containing the benzotriazole cycle (particularly 2-(2-hydroxy-5-methylphenyl)benzotriazole-N-oxide). The almost linear correlation between the selectivity of the catalytic hydrogenation of isomers of nitro-2'-hydroxy-5'-methylazobenzene and the kinetic characteristics of the hydrogenation of nitro and azo groups in compounds containing a single reactive substituent at different values of medium’s pH is estimated.

Solubility of mesalazine in {1-propanol/water} mixtures at different temperatures

Mesalazine solubility is important to study in solvent mixtures for chemical and pharmaceutical engineering. Therefore, solubility of the drug was determined in water/1-propanol mixtures at T = (293.2 to 313.2) K. To represent the solid-liquid equilibrium for these systems, the van't Hoff, Apelblat, combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K), modified Wilson, Jouyban-Acree, Jouyban-Acree-van't Hoff, Wilson, NRTL and UNIQUAC models were employed. The thermodynamic quantities of dissolution and mixing were calculated for mesalazine in aqueous 1-propanol solutions at harmonic temperature. Further, calculations of inverse Kirkwood-Buff integrals show that this drug is preferentially solvated by water in all the mixtures, with exception of x1 = 0.20, at 298.2 K.

Conductometric investigation of ceftriaxone disodium in aqueous solutions of 1-propanol and 2-propanol

Often common organic solvents have been used in extraction and purification of ceftriaxone disodium from aqueous solution. Therefore, in this study the conductometric properties of ceftriaxone disodium were investigated in aqueous solutions of 1-propanol and 2-propanol at T/K = (288.15–308.15). The conductivities data were analysed by Fuoss-Onsager conductivity equation. The obtained results indicate that the molar conductivity increases with temperature. Also, the molar conductivity increases with increasing concentration of 1-propanol and 2-propanol. The activation enthalpy of charge transfer is calculated from the temperature dependency of molar conductivity. The activation enthalpy of charge transfer in water is lower than that of aqueous solutions of 1-propanol and 2-propanol. The calculated Walden products reveal that ion-solvent interactions in aqueous solutions of 1-propanol and 2-propanol are weaker than that of water.

INTERRELATION BETWEEN CATALYTIC REDUCTION RATE AND SOLUBILITY OF NITROBENZOIC ACID ISOMERS

The solubility of nitrobenzoic acid isomers is determined from the concentration of solution in equilibrium with the solid phase at a temperature of 303 K in an azeotropic aqueous solution of 2-propanol, including additives of acetic acid and sodium hydroxide, with an error of no more than 5%. It is shown that the lowest solubility in all these media is observed for para-nitrobenzoic acid, and the maximum for the meta-isomer. The addition of acid or base to the liquid phase assists an increase in solubility for all isomers of nitrobenzoic acid. The most significant changes in solubility occur in the presence of sodium hydroxide in the water-alcohol solvent. The shift of the maxima in the absorption spectra was compared with the change in the solubility value. It has been established that with increasing solubility, the rate of liquid phase catalytic hydrogenation of nitrobenzoic acid isomers on the skeletal nickel catalyst decreases. А linear correlation between the solubility of reagents and the rate of their reduction is revealed. The observed interrelation for para- and meta-isomers in neutral and acidic aqueous-alcoholic media is mostly caused by the influence of solubility on the adsorption ability of the hydrogenated compound on the surface of the nickel catalyst. Deviations from this dependence in the presence of sodium hydroxide can be explained by ionization of the of nitrobenzoic acid isomers molecules and by redistribution of the forms of hydrogen adsorbed on the surface of the nickel catalyst. The reason of the distinction in a similar correlation for isomers with a substituent in the ortho-position relative to the nitrogroup is the possibility for forming an intramolecular hydrogen bond in all used media.

Photochemical and photocatalytic degradation of 1-propanol using UV/H2 O2 : Identification of malonate as byproduct.

1-propanol is a primary alcohol extensively used in the pharmaceutical, chemical, and food industries. It has been also found as a contaminant in the atmosphere and is considered a model compound to mimic the behavior and fate of aliphatic alcohols exposed to environmental conditions. In order to understand that role of relevant variables, this paper presents results obtained with a simple experimental set-up to investigate the reactivity of 1-propanol under mild oxidizing conditions. Coupling this system with CE-C4 D allowed the quantification of the carboxylic acids formed. For the described experiments, aqueous solutions of 1-propanol were placed inside a photoreactor and oxidized upon the addition of TiO2 and/or H2 O2 . According to the described results, the addition of H2 O2 (0.1% w/w) was the most significant variable, roughly tripled the amount of carboxylic acids generated and led to the conversion of up to 70% of the initially available 1-propanol (1mmol/L). More importantly, the reaction yielded the formation (within 10 min) of propionate (50µmol/L), acetate (400µmol/L), formate (50µmol/L), and malonate (200µmol/L). The latter is critically important because it represents the first example of the photochemical oxidation of both terminal carbons of the C3 -chain of 1-propanol under mild conditions, and opens new avenues for the production of this important chemical building block.

HYDROGENIZATION OF SUBSTITUTED NITRO-, AZOBENZENES, THEIR MIXTURE AND SUBSTITUTED NITROAZOBENZEN ON SKELETAL NICKEL IN AQUEOUS 2-PROPANOL SOLUTIONS

The article is devoted to the investigation of the hydrogenation of 4-nitroaniline, 4-amino-2'-hydroxy-5'-methylazobenzene, their mixture and 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in an aqueous solution of 2-propanol with azeotropic composition (x2 = 0.68) and this solvent with the addition of acid (0.01 M CH3COOH) or sodium hydroxide (0.01 M NaOH). The elucidation of the reasons and the development of approaches to the selective control of the staged transformations of substituted nitroazobenzenes containing two reactive groups in a molecule under the conditions of hydrogenation are of interest from theoretical and practical points of view. The rate of formation of intermediate products during the hydrogenation of nitroazobenzenes is largely determined by the activation of nitro and azo groups. The aim of the work is to conduct a comparative analysis of the rates of conversion of nitro- and azogroups in individual compounds with the rates of hydrogenation of their mixture and the rate of conversion of nitroazobenzene, which simultaneously contains nitro- and azogroups, to discuss the reasons for the influence of the solvent composition on the conversion rates of mono- and disubstituted benzenes. UV-spectroscopic data indicate that the electronic state of the hydrogenated compounds in the solvent compositions used does not undergo significant changes, since the absorption maxima are shifted by no more than 1 nm, both with the addition of acid and base. On the contrary, the observed rates of hydrogenation of mono- and disubstituted benzenes vary within fairly wide limits. A comparative analysis of the rates of hydrogenation of individual compounds, their mixtures and disubstituted benzene allows us to conclude that the priority of reduction of one or another group in 4-nitro-2'-hydroxy-5'-methyl-azobenzene can be made on the basis of calculating the quantitative ratio of the reaction products. When a mixture of compounds containing nitro and azo groups is hydrogenated, their adsorption rather than reactivity begins to play the primary role.

Dynamics of Complete Evaporation of a Sessile Droplet of 1-Propanol–Water Solution at Different Ambient Humidities

Experimental data have been obtained on the complete diffusion evaporation of a sessile microdroplet of an aqueous 1-propanol solution on a hydrophobized polished quartz substrate in air at atmospheric pressure and room temperature. During the evaporation of the sessile droplet, time dependences have been determined for its key thermodynamic and geometric parameters, i.e., the contact angle, base surface area, and volume. It has been revealed that the character of time variations in the contact angle depends on the initial alcohol concentration in the droplet and air humidity. At a high alcohol concentration and a low air humidity, the droplet contact angle monotonically decreases throughout the evaporation process. The contact angle of a solution droplet with a prevailing content of water varies in several stages. In this case, the monotonic reduction in the contact angle is, at a certain moment, replaced by a stage of its growth. The comparison of the maximum contact angle of an evaporating droplet with the contact angle of a sessile droplet of pure water enables one to determine the amount of alcohol in a studied droplet by the end of this stage. The residual alcohol amount governs the subsequent evolution of the droplet up to its complete evaporation.

INFLUENCE OF SODIUM HYDROXIDE ADDITIVES ON HYDROGENIZATION KINETICS OF 4-NITRO-2'-HYDROXY-5'-METYLAZOBENZENE ON SKELETAL NICKEL IN AQUEOUS SOLUTION OF 2-PROPANOL

The elucidation of the sequence of transformations in compounds containing several reactive groups and the development of approaches to controlling the selectivity of the processes with their participation is of interest both from the theoretical and practical points of view. The article is devoted to the analysis of the kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in aqueous solution of 2-propanol with addition of sodium hydroxide on skeletal nickel at different initial amounts of the starting compound. An increase in the initial amount of 4-nitro-2'-hydroxy-5'-methylazobenzene leads to an increase in the rate of conversion of the nitro group in the starting compound and to a decrease in the rate of conversion of the azo-group. The effect of the introduced sodium hydroxide in the neutral solvent 2-propanol-water on the rate of conversion of the nitro and azo-groups to 4-nitro-2'-hydroxy-5'-methylazobenzene is consistent with the nature of the rate changes for the hydrogenation of individual compounds containing nitro and azo-groups, in the quality of which 4-nitroaniline and 4-amino-2'-hydroxy-5'-methylazobenzene were chosen. The results obtained do not contradict the notion of a parallel-sequential scheme of 4-nitro-2'-hydroxy-5'-methylazobenzene transformations. One of the directions involves the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene due to the hydrogenation of the azo-group to 4-nitroaniline and PC, and the second one is the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene through 4-amino-2'-hydroxy-5'-methylazobenzene due to the reduction of the nitro group. By the end of the reaction, all the intermediate compounds are restored to PC and 1,4-phenylenediamine. When sodium hydroxide is introduced into the neutral solvent 2-propanol-water, the effect of the direction providing the formation of 4-amino-2'-hydroxy-5'-methylazobenzene to the overall reaction rate increases. It was experimentally established that the amount of 4-amino-2'-hydroxy-5'-methylazobenzene during the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of sodium hydroxide increases by 15%, on the contrary, the amount of 4-nitroaniline decreases by 4 % in comparison with the neutral solvent.

The solubility of bosentan in aqueous-2-propanol mixtures at several temperatures, measurement and data correlation

ABSTRACTThe solubilities of bosentan (BST) in binary aqueous mixtures of 2-propanol at temperatures ranging from 293.15 to 313.15 K were determined using a shake-flask method. The produced data were modelled with the Jouyban-Acree-van’t Hoff model and difference between the predicted data and experimental ones were illustrated by percent average relative deviations (%ARD). Moreover, the thermodynamic functions of dissolution for BST in the aqueous 2-propanol solutions were computed which suggest that the dissolution process is endothermic and not spontaneous.

KINETICS OF HYDROGENATION OF NITROBENZENE, 4-NITROTOLUENE, 4-NITROANILINE AND 2-CHLORO-4-NITROANILINE ON SUPPORTED PALLADIUM CATALYST

A study of the kinetics of liquid phase hydrogenation of nitrobenzene, 4-nitrotoluene, 4-nitroaniline and 2-chloro-4-nitroaniline on supported palladium catalyst in aqueous solutions of 2-propanol of different composition was carried out. The influence of the substituent on the value of the total amount of hydrogen absorbed during the reaction and the kinetics of the hydrogenation of substituted nitrobenzenes was discussed. It was found out that the reaction selectivity to 2-chloro-1,4-phenylenediamine decreases due to by-reaction dehalogenation. The degree of dehalogenation depends on the composition of solvent and may be approximately estimated by the values of the absorbed hydrogen volume during the reaction. Also, the presence of the donor-acceptor substituents is capable of exerting influence on the reaction rate of hydrogenation of the nitro compound.

ACETONE HYDRATION KINETICS AND EVALUATION OF INPUT OF 2-PROPANOL DEHYDRATION REACTION ON RANEY NICKEL UNDER HYDROGENATION CONDITIONS

The problem of kinetics of skeletal nickel samples saturation with hydrogen in an aqueous solution of 2-propanol of azeotropic composition was discussed. 2-propanol dehydrogenation and acetone hydrogenation rate constants were calculated. Kinetic model of processes under study was offered.