The methods of theoretical description of the patterns of changes in thermodynamic properties depending on the composition and structure of solution components are a priority direction in the development of the theory of solutions. This article is devoted to the establishment of relationships between the thermodynamic properties, composition of solutions, and the structure of their components. The study of the thermodynamic properties of binary solutions formed by a common solvent (ethylbenzene) and substances of the homologous series of n-alkylbenzenes contributes to the establishment of the aforementioned relationships. In the production of ethylbenzene and its homologues, solutions based on n-alkylbenzenes are quite common. Alkylbenzenes are widely used in various fields of science and chemical technology as solvents, extractants, and plasticisers. Using the ebuliometric method, we measured the boiling points of solutions of four binary systems formed by ethylbenzene and n-alkylbenzenes under various pressure values. Compositions of equilibrium vapour phases of the binary systems were calculated using the obtained isotherms of saturated vapour pressure of the solutions. Using the Runge-Kutta method, the composition of the vapour phases of the solutions of the systems was calculated by the numerical integration of the Duhem–Margules equation on a computer. The obtained data on the vapour-liquid equilibrium became the basis for calculating the thermodynamic functions of the systems’ solutions. The Gibbs and Helmholtz energy values, the enthalpies of vaporisation and mixing, the internal energy, and entropy of solutions were calculated. The thermodynamic properties of the solutions were calculated using a comparison of the values baed on two standards: an ideal solution and an ideal gas. It was found that the values of the Helmholtz energy linearly depend on the molar mass of the substance (the number of –CH2– groups in a molecule) in the homologous series of n-alkylbenzenes. An increase in the Helmholtz energy values for n-alkylbenzenes in the homologous series is associated with a linear increase in the molar volume of liquid substances and an exponential decrease in the saturated vapour pressure of substances. For binary solutions of constant molar concentrations formed by ethylbenzene and n-alkylbenzenes, the Helmholtz energy linearly depends on the molar mass (number of –CH2– groups in the molecule) of n-alkylbenzene in the homologous series. We obtained an equation that makes it possible to predict the thermodynamic properties of solutions of binary systems with high accuracy. The equation accelerates the process of studying vapour-liquid phase equilibria and thermodynamic properties of solutions of binary systems by 300 times. The determined patterns confirm the hypothesis of the additive contribution of functional groups to the thermodynamic properties of solutions. This hypothesis underlies the statistical theory of group models of solutions. The thermodynamic patterns determined by this study can also be used to solve a wide range of technological issues in the chemical industry.
As is known, some water-soluble polyelectrolytes (glycans, nucleic acids, synthetic polycarboxylic acids and their copolymers with pyridine derivatives, etc.) exhibit adjuvant properties when introduced into the organism together with antigens [1]. However, most of the synthetic polyelectrolytes exhibit increased toxicity, which is an obstacle for their use in immunolo~cal research [2]. A promising way to the creation of low-toxicity polymers possessing immunomodulator properties consists in the chemical modification of glycans that are characterized by detoxicating effect and are capable of prolonging and au.~aenting the action of drugs used for chemotherapy. Smirnova et al. [3] reported on the synthesis of an oxyglycan based on mannan, a microbial poIysaccharide capable of stimulating the immune response [3].The purpose of this work was to synthesize nontoxic water-soluble polymers (analogs of oxystarch and inulin), containing amino acid and hydroxyalkyl(alkyl)amino groups and study their biolo~cal activity.The oxystarch was obtained through the oxidation of starch by the persulfate method, whereby 12% aldehyde and 8% carboxy groups (occupying predominantly the C o and C 3 positions) are formed in the structure [4].The starch-based cation-active derivatives were synthesized by interaction of oxyglycan with (3-chloro-2-hydroxypropyl)tri(2-hydroxyethyl)ammonium chloride or triethylamine with the formation of ethers and salts (I and II, respectively). The carionization of inulin was performed by, its interaction with di(2-hydroxyethyl)amine and formaldehyde (the Marmieh reaction). The resulting amino-containing ethers are probably substituted at the C 6 site (V). The results of periodate oxidation indicate that OH groups in positions C 3 and C 4 (a-glycol group) are free (as is known, some structtaaI features of inulin hinder substitution of these hydroxy groups) [5,6]. 80,c3/H~H OH Starch analogs of the ampholytic type were obtained by the reaction of oxystarch with N-0aydroxymethyl)-L-gluramie acid (leading to the formation of iminium-salt structural elements with an aldehyde group conversion from 3 to 12%, IVa-IVc) and lysine (with the formation of azomethine group, liD. Compounds I-V were synthesized in an aqueous medium at a temperature of 50-70~ The structures of polymer analogs were confirmed by IR spectroscopic data and the results of elemental analyses. EXPERIMENTAL CHEMICAL PARTThe IR spectra of synthesized compounds were measured on an IKS-29 spectrophotomcter.Compounds I -V were purified by ultrafiltmtion through fluoroplastic membranes with a pore diameter of 50 A for compound V and 200 A for compounds I -IV.
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