Kharkov University Bulletin Chemical Series

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ISSN / EISSN : 2220637X / 22206396
Current Publisher: V. N. Karazin Kharkiv National University (10.26565)
Total articles ≅ 76
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Anton B. Zakharov, Vladimir V. Ivanov
Kharkov University Bulletin Chemical Series pp 38-45; doi:10.26565/2220-637x-2019-32-02

Abstract:
A new look on the problem of the molecular systems index description is presented. The capabilities of iterated line (edge) graphs in characterization of saturated hydrocarbons properties were investigated. It was demonstrated that single selected molecular (graph-theoretical (topological) or informational) descriptor calculated for the sequence of nested line graphs provides quite reliable progressive set of regression equations. Hence, the problem of descriptor set reduction is solved in the presented approach at list partially. Corresponding program complex (QUASAR) has been implemented with Python 3 program language. As the test example physico-chemical properties of octane isomers have been chosen. Among the properties under investigation there are boiling point, critical temperature, critical pressure, enthalpy of vaporization, enthalpy of formation, surface tension and viscosity. The corresponding rather simple linear regression equations which include one, two or three parameters correspondingly have been obtained. The predictive ability of the equations has been investigated using internal validation tests. The test by leave-one-out (LOO) validation and Y‑scrambling evaluate the obtained equations as adequate. For instance, for the regression model for boiling point the best equation characterizes by determination coefficients R2 = 0.943, with LOO procedure – Q2 = 0.918, while for the Y-scrambling test Q2y-scr
Margaret M. Blazhynska, Alexander V. Kyrychenko, Oleg N. Kalugin
Kharkov University Bulletin Chemical Series pp 46-58; doi:10.26565/2220-637x-2019-32-03

Abstract:
Contact of silver metal surfaces with water, ions and organic ligands experiences induced charges, leading to attractive polarization. These forces play an important role at inorganic/organic interfaces and complement other non-bonded surface interactions. Despite the importance of these interactions, it, however, remains difficult to implement polarization effects to classical molecular dynamics (MD) simulations. In this contribution, we first present an overview of two popular polarizable models, such as Drude oscillator and the rigid rod model, which are utilized to mimic the polarizability of bulk metals. Second, we implemented the rigid rod model to the polarizable force field (FF) for a silver atom, which was further adapted for atomistic MD simulations of silver nanoparticles (AgNPs) composed of 1397 atoms. In our model, induced charge polarization is represented by the displacement of a charge-carrying virtual site attached rigidly to an original Ag atom. To explore the role of polarization, we compared the performance of the classical nonpolarizable FF and the new polarizable model in the MD simulations of adsorption of water and ions onto quasi-spherical AgNP and the flat crystalline silver surface. The analysis of the radial distribution function of Ag-Ag atoms demonstrated that the introduction of the polarization effect had minor effects on face-centered cubic (fcc) packing of silver atoms of bare and water-solvated AgNPs. We found that the polarizable FF causes some increase in attractive interactions between the silver surface and water molecules and Na+ ions. As a crucial test of the developed polarizable model, the structure of adsorbed interfacial water molecules was analyzed. Our data suggest that the environment-induced polarization of the silver surface contributes significantly to the structure of adsorbed interfacial water layers and it also plays an important role in the adsorption of positive ions. However, it was also found out that the polarization effect has a rather short-range effect, so that a minor contribution of silver polarization was seen for adsorption of water molecules and ions from distant solvation shells.
N. N. Kolos, Natalia V. Chechina
Kharkov University Bulletin Chemical Series pp 67-75; doi:10.26565/2220-637x-2019-32-05

Abstract:
We have developed some available and effective methods for the synthesis of substituted pyrrolo[2,3-d]pyrimidines and 5,8-dihydropyrido[2,3-d]pyrimidines based on the three-component condensation of 6-amino-2-thiouracil with arylglyoxal hydrates and N,N-dimethylbarbituric acid or acyclic β-dicarbonyl compounds: acetylacetone (acetoacetic ester). It was shown that the optimal product yields were obtained by boiling the reagents in acetic acid. Thus, the synthesis of pyrrolo[2,3-d]pyrimidines took 15-20 minutes, while the precipitation of 5,8‑dihydropyrido[2,3-d]pyrimidines formed only after 2 hours. We proposed possible mechanisms for the formation of anelated pyrrole and pyridine rings. In both cases, the reaction includes the formation of an intermediate of α,β-unsaturated ketone with the participation of arylglyoxal and CH-acid (N,N-dimethylbarbituric or acetylacetone (acetoacetic ester)), nucleophilic addition of 6-aminothiouracil via an activated double bond, condensation of carbonyl and amino groups. The formation of the cycle takes place exclusively with the participation of the acetyl moiety, while the pyrrol one forms during the condensation of the aroyl moiety and the 6-amino group of thiouracil. A series of synthesized pyrrolo[2,3-d]pyrimidines was modified by alkylation. As it was expected, alkylation proceeds at the sulfur atom, that allowed a significant increase in the solubility of the obtained products. The reaction was carried out in DMF by stirring the initial reagents at 60ºC (reaction with methyl iodide) or boiling them (alkylation with phenacyl bromide), whereby S-methyl and S-phenacyl derivatives of pyrrolo[2,3-d]pyrimidines were obtained. The spectral data of 1H NMR showed that S-methylation products form solvates with DMF as 1:1. The synthesized compounds can become the basis to create small libraries of anelated pyrimidines with improved antiviral activity profile.
Anastasia Yu. Kharchenko, Maria A. Romakh, Karolina V. Yanova, Marina N. Tereshchuk, Nikolay O. Mchedlov-Petrossyan
Kharkov University Bulletin Chemical Series pp 65-76; doi:10.26565/2220-637x-2019-33-05

Abstract:
In this paper, the properties of cationic polyelectrolytes as tools for governing the protolytic equilibrium of acid-base indicators in water were examined. For this purpose, water-soluble and pH-dependent poly (hexamethylene guanidine hydrochloride), PHMG, and poly (diethylenamine guanidine hydrochloride), PDEG, were studied. As molecular probes, a set of anionic indicator dyes were used; the key parameter is the so-called apparent ionization constant, Kaapp. The electrokinetic potential of the above polycationic species in the acidic pH region is substantially positive. As a rule, the polyelectrolytes display marked influence on the absorption spectra and state of the acid-base equilibrium of the anionic dyes at pH < 7, especially in the case of PHMG. Both effects resemble those known for the same dyes in aqueous solutions of cationic surfactants but are less expressed. Normally, the acid-base equilibria were studied at polyelectrolyte : dye ratio of 150 : 1, at ionic strength 0.05 M, and 25 oC. The decrease in the pKaapp (≡ –logKaapp) value on going from water to the PHMG solution is most expressed for bromocresol green (HB– ↔ B2– + H+): pKa,2app – pKa,2w = –1.93. For bromophenol blue, bromocresol purple, and sulfonefluorescein, the shift of the equilibrium is less expressed. Some kinds of specific interactions with the polyelectrolytes were revealed for methyl orange and bromophenol blue. Also, the dependence of pKaapp on logarithm of ionic strength allows estimating the degree of counterion binding by the polycation: β = 0.40.1. В настоящей статье исследованы свойства катионных полиэлектролитов как средства управления протолитическими равновесиями кислотно-основных индикаторов в воде. С этой целью изучены водорастворимые pH-зависимые поли (гексаметилен гуанидин гидрохлорид), ПГМГ, и поли (диэтиламин гуанидин гидрохлорид), ПДЕГ. В качестве молекулярных зондов использован набор анионных индикаторных красителей, при этом ключевым параметром являются так называемые кажущиеся константы ионизации, Kaapp. Электрокинетический потенциал обоих катионных макромолекул в кислой области pH существенно положительный. Как правило, исследованные полиэлектролиты оказывают заметное влияние на спектры поглощения и положение кислотно-основных...
Dmytro S. Dudariev, Kate O. Logacheva, Yaroslav V. Kolesnik, Oleg N. Kalugin
Kharkov University Bulletin Chemical Series pp 54-64; doi:10.26565/2220-637x-2019-33-04

Abstract:
Ionic liquids have gained immense popularity in recent decades due to a combination of unique properties. Despite the widespread use of ionic liquids mixtures with aprotic dipolar solvents in electrochemistry, it remains relevant to predict their macroscopic, primarily transport, properties based on the microscopic picture of the entire set of interparticle interactions in such systems. The method of molecular dynamics simulation (MDS) is one of the most powerful tools for solving problems of this kind. However, one of the unsolved problems of the classical MDS of ion-molecular systems is the correct accounting of polarization effects. Recently it was proposed to use a variation of the effective ion charges in solutions to solve this task. This paper presents the results of the MDS structural and dynamic properties of 1-butyl-3-methylimidazolium (BmimBF4) and lithium (LiBF4) tetrafluoroborates solutions in propylene carbonate (PC) at 298.15 K in NPT ensemble using GROMACS and MDNAES software packages. The possibility of reproducing the experimental dynamic properties (diffusion coefficients of cations and solvent, viscosity, and electrical conductivity) of binary systems based on mixtures of ionic liquids with PC in a wide concentration range was shown. Polarization effects were taken into account by reducing the partial charges of the ion atoms. The structure of the solvation shell of cations was studied within the framework of radial distribution functions, distribution of coordination numbers and the presence of hydrogen bonds between the organic cation and solvent molecules. The results point to stronger and more structured solvation shell of the Li+ cation compared to Bmim+, which is consistent with the conclusions about the mobility of these cations. The reorientation times of propylene carbonate molecules and their lifetimes in the framework of the first solvation shells of the cations are several times higher for the lithium cation. Ионные жидкости приобрели огромную популярность в последние десятилетия благодаря комплексу уникальных свойств. Несмотря на широкое использование смесей ионных жидкостей с апротонными диполярными растворителями в электрохимии, актуальным остаётся прогнозирование их макроскопических, в первую очередь транспортных, свойств исходя из микроскопической картины всей совокупности межчастичных взаимодействий в таких системах. Метод молекулярно-динамического моделирования (МДМ) является одним из наиболее мощных инструментов решения подобного рода задач. Однако одной из нерешённых проблем классического МДМ ион-молекулярных систем является...
A.A. Kityk, N. G. Bannyk, Elena V. Kun
Kharkov University Bulletin Chemical Series pp 59-66; doi:10.26565/2220-637x-2019-32-04

Abstract:
It is shown that deep eutectic solvent Ethaline is an environmentally friendly and highly efficient medium for electropolishing of AISI 304 stainless steel that is widely used for medical products. The obtained voltammograms allow choosing optimal conditions for anodic treatment of AISI 304 steel samples in Ethaline at different temperature conditions (from 20 to 50°C) and with water additives (up to 10 %). It is established that high efficiency of Ethaline as an electrolyte for anodic treatment is primarily associated with its unique physicochemical properties: significant viscosity and, at the same time, relatively high, as for ionic liquids, electrical conductivity. The high viscosity of the Ethaline solvent causes slow diffusion of the products of anodic dissolution of steel, which achieve the formation of a viscous electrode layer and provide a high efficiency of the polishing process. It has been shown that with an increase in electrolyte temperature and water content in Ethaline the anodic dissolution rate of steel increases and this allows the use of high anode current densities for electropolishing in galvanostatic mode or lower potentials in the potentiostatic mode.
A. V. Luzanov
Kharkov University Bulletin Chemical Series pp 6-37; doi:10.26565/2220-637x-2019-32-01

Abstract:
A synthetic review and new results are given of the alternant symmetry theory and its applications within a unified approach. It is based on J–symmetry (parity) operators. Unlike usual commutation rules, these symmetry operators anticommute with Hamiltonians or other relevant quantities. In the J–symmetry terms we treat a variety of problems and topics, mainly related to π-shells of conjugated molecules. In particular, various orbital theories are outlined with a systematic use of block-matrix technique (density matrices, operator functions etc.). Noval π‑models and their J–symmetry are studied within the current context of single-molecule conductance and the relevant problems concerning Green’s function and electron transmission evaluation. We stress on the key importance of account for π-electron correlation for describing correctly transmission π-spectra. We discuss electron-structure peculiarities of alternant radical states and the validity of the Lieb-Ovchinnikov spin rule resulting from the J–symmetry and electron correlation effects. It is shown how the simplified (based on Hückel’s MOs) spin-polarized theory provides a correct number of effectively unpaired electrons in polyradicaloid alternant molecules. Another type of problems is concerned with chirality (generllly, structural asymmetry) problems. By spectral analysys of the previously defined chirality operator we could reinterpret the problem in terms of J–symmetry. It allowed us to construct here the noval chirality operator which is nonnegative definite and vanishes on achiral structures. Its simplest invariant, the matrix trace, surves us as a quantitative measure of the structural (electronic) chirality. Preliminary calculations tell us that the new chirality index behaves reasonably even for the difficult (high-symmetry) chiral systems.
Masashi Hojo
Kharkov University Bulletin Chemical Series pp 6-22; doi:10.26565/2220-637x-2019-33-01

Abstract:
It has been discovered that dilute nitric acid in reversed micelle systems can oxidize the Br- ion to Br2 and we have proposed that the nitryl (or nitronium) ion NO2+ should be the active species in the oxidation process. Nitration of phenol in reversed micelle systems with dilute nitric acid, CHCl3/CTAC/H2O (2.0 mol dm-3 HNO3 in the 1.0% (v/v) H2O phase), has been performed at 35 ºC to obtain 2- and 4-nitrophenols, where CTAC represents cetyltrimethylammonium chloride. In aqueous 2.0 mol dm-3 HNO3 solution accompanied by 4.0 mol dm-3 LiCl (and a small amount of LiBr as the bromide resource), trans-1,4-dibromo-2-butene was successfully brominated to 1,2,3,4-tetrabromobutane. This result is good evidence that the Br- ion can be oxidized to Br2 in dilute nitric acid (2.0 mol dm-3) providing it contains concentrated salts. For chloride salts, the cation effects increased as Et4N+
Igor S. Vovchynskyi, Oleg N. Kalugin
Kharkov University Bulletin Chemical Series pp 37-53; doi:10.26565/2220-637x-2019-33-03

Abstract:
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