Pub Date : 2021-11-03DOI: 10.26565/2220-637x-2021-37-04
S. Kulish
The article identifies a number of problems that arose in the process of training students in chemistry at Ukrainian universities in the 19th – early 20th centuries. There were not enough chemistry teachers during this period, but they did a lot of work to find ways to stimulate students’ research, although chemical laboratories were insufficiently equipped and staffed. The role of university professors in public life and everyday problems of the population of Ukraine is shown. They participated in the preparation of literature for the population of Kharkiv and Odessa, provided assistance in studying the physical and chemical properties of products and non-product substances. During this period, new areas of focus emerged in the study of chemistry (agrochemistry, thermochemistry, electrochemistry, etc.). The problems of various scientific schools in chemistry, which led to conflicts among lecturers, university administrations and the Ministry of Public Education, are considered. During this period, the authorities tightened control over the national factor of university teachers. At the end of the 19th century the Ministry of Public Education demanded to strengthen the Russian element in the teaching staff, refrained from hiring teachers of the Jewish and Catholic religion. The article also considers the problems of scientific trips of teachers abroad and the use in teaching students of foreign experience in teaching chemistry.
{"title":"Problems of training scientific and pedagogical staff in chemistry in pre-revolutionary universities of Ukraine (19th – early 20th centuries)","authors":"S. Kulish","doi":"10.26565/2220-637x-2021-37-04","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-37-04","url":null,"abstract":"The article identifies a number of problems that arose in the process of training students in chemistry at Ukrainian universities in the 19th – early 20th centuries. There were not enough chemistry teachers during this period, but they did a lot of work to find ways to stimulate students’ research, although chemical laboratories were insufficiently equipped and staffed. The role of university professors in public life and everyday problems of the population of Ukraine is shown. They participated in the preparation of literature for the population of Kharkiv and Odessa, provided assistance in studying the physical and chemical properties of products and non-product substances.\u0000\u0000During this period, new areas of focus emerged in the study of chemistry (agrochemistry, thermochemistry, electrochemistry, etc.). The problems of various scientific schools in chemistry, which led to conflicts among lecturers, university administrations and the Ministry of Public Education, are considered. During this period, the authorities tightened control over the national factor of university teachers. At the end of the 19th century the Ministry of Public Education demanded to strengthen the Russian element in the teaching staff, refrained from hiring teachers of the Jewish and Catholic religion. The article also considers the problems of scientific trips of teachers abroad and the use in teaching students of foreign experience in teaching chemistry.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47839479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-07DOI: 10.26565/2220-637x-2021-37-03
Maksym Pokhmura, V. Cheranovskii
The work is devoted to the theoretical simulation of low-temperature magnetic properties of generalized polyallyl spin chain with the antiferromagnetic coupling of the neighboring spins (GPSC) - spin model of a family of quasi-one dimensional molecular ferrimagnets. First, the exact energy spectra of Heisenberg spin Hamiltonians of the finite lattice clusters of GPSC with the spins of the main chain s=1/2 and pendant spins š=1 have been studied by means of the exact diagonalization method. The calculations were performed for different positive values of the coupling parameters for neighboring spins of the main chain of GPSC clusters. On the base of the above exact energy spectra and the Boltzmann distribution law the field dependencies of magnetization of finite lattice clusters are calculated numerically at different temperatures. In the result, for low temperatures the presence of intermediate plateau in field dependencies of the cluster magnetization has been shown. These calculations demonstrated the stabilization of the intermediate magnetization plateau with the growth of the spin coupling along the main chain of GPSC clusters. In addition, the numerical study of temperature dependence of zero field magnetic susceptibility of 12- spin clusters of GPSC gives the results which are similar to the 1D model of molecular ferrimagnets like necklace spin ladder. Similar calculations of the magnetization profile were performed for infinite Heisenberg –Ising GPSC model with Ising type of the antiferromagnetic interactions between the neighboring spins of the main chain. The classical transfer- matrix method was used for this purpose. In the result, it was shown the presence of an intermediate plateau in the low-temperature magnetization profile of infinite chain model and the increase of the plateau size with increasing of the Ising coupling between the spins of the main chain.
{"title":"Magnetic properties of generalized polyallyl spin chain","authors":"Maksym Pokhmura, V. Cheranovskii","doi":"10.26565/2220-637x-2021-37-03","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-37-03","url":null,"abstract":"The work is devoted to the theoretical simulation of low-temperature magnetic properties of generalized polyallyl spin chain with the antiferromagnetic coupling of the neighboring spins (GPSC) - spin model of a family of quasi-one dimensional molecular ferrimagnets. First, the exact energy spectra of Heisenberg spin Hamiltonians of the finite lattice clusters of GPSC with the spins of the main chain s=1/2 and pendant spins š=1 have been studied by means of the exact diagonalization method. The calculations were performed for different positive values of the coupling parameters for neighboring spins of the main chain of GPSC clusters. On the base of the above exact energy spectra and the Boltzmann distribution law the field dependencies of magnetization of finite lattice clusters are calculated numerically at different temperatures. In the result, for low temperatures the presence of intermediate plateau in field dependencies of the cluster magnetization has been shown. These calculations demonstrated the stabilization of the intermediate magnetization plateau with the growth of the spin coupling along the main chain of GPSC clusters. In addition, the numerical study of temperature dependence of zero field magnetic susceptibility of 12- spin clusters of GPSC gives the results which are similar to the 1D model of molecular ferrimagnets like necklace spin ladder.\u0000\u0000Similar calculations of the magnetization profile were performed for infinite Heisenberg –Ising GPSC model with Ising type of the antiferromagnetic interactions between the neighboring spins of the main chain. The classical transfer- matrix method was used for this purpose. In the result, it was shown the presence of an intermediate plateau in the low-temperature magnetization profile of infinite chain model and the increase of the plateau size with increasing of the Ising coupling between the spins of the main chain.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46778486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-21DOI: 10.26565/2220-637x-2021-37-02
V. Lipson, Karyna Kulyk
The article is an overview of the latest achievements in the study of low molecular weight gelling agents based on steroids - cholesterol, estradiol, dehydroepi-androsterone and pentacyclic triterpenoids - arjunolic, glycyrrhetinic acids. These compounds are used as components of smart gels and are of interest for supramolecular chemistry. A gelling agent is a substance that is able to bind various solvents at low concentrations, and the resulting gel has a solid structure which rheological properties are similar to those of solids. Non-covalent interactions: dipole-dipole, van der Waals, electrostatic, hydrogen bonds and π-stacking, are considered as the driving forces for the formation a fibrous network by low molecular weight gelator. In contrast to decades of research into the gelation of polymers, proteins and inorganic substances, low molecular weight organic gelling agents have only recently begun to be actively studied. Their chemical structure is derived from urea, amino acids, carbohydrates, cholesterol and bile acids. Unlike steroid-based gels, information on the use of pentacyclic triterpenoids for the development of low molecular weight gelling agents is extremely limited. The interest in such systems is due to the fact that, like steroids, they have a developed, rigidly organized nanosized molecular platform, making them capable of self-association in polar and nonpolar organic solvents. In addition, the presence of molecules of these compounds in several functional groups that are easily chemically modified, low toxicity and biocompatibility allows them to be considered as promising starting materials for the pharmaceutical industry, in particular for the development of mild dosage forms.
{"title":"Low molecular weight gelators based on steroid derivatives and pentacyclic triterpenoids","authors":"V. Lipson, Karyna Kulyk","doi":"10.26565/2220-637x-2021-37-02","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-37-02","url":null,"abstract":"The article is an overview of the latest achievements in the study of low molecular weight gelling agents based on steroids - cholesterol, estradiol, dehydroepi-androsterone and pentacyclic triterpenoids - arjunolic, glycyrrhetinic acids. These compounds are used as components of smart gels and are of interest for supramolecular chemistry. A gelling agent is a substance that is able to bind various solvents at low concentrations, and the resulting gel has a solid structure which rheological properties are similar to those of solids. Non-covalent interactions: dipole-dipole, van der Waals, electrostatic, hydrogen bonds and π-stacking, are considered as the driving forces for the formation a fibrous network by low molecular weight gelator. In contrast to decades of research into the gelation of polymers, proteins and inorganic substances, low molecular weight organic gelling agents have only recently begun to be actively studied. Their chemical structure is derived from urea, amino acids, carbohydrates, cholesterol and bile acids. Unlike steroid-based gels, information on the use of pentacyclic triterpenoids for the development of low molecular weight gelling agents is extremely limited. The interest in such systems is due to the fact that, like steroids, they have a developed, rigidly organized nanosized molecular platform, making them capable of self-association in polar and nonpolar organic solvents. In addition, the presence of molecules of these compounds in several functional groups that are easily chemically modified, low toxicity and biocompatibility allows them to be considered as promising starting materials for the pharmaceutical industry, in particular for the development of mild dosage forms.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42768346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-03DOI: 10.26565/2220-637x-2021-37-01
A. Doroshenko, M. Kolosov, N. Mchedlov-Petrossyan, A. Korobov
{"title":"To the 80th anniversary of the birthday of professor Valeriy Dmytrovych Orlov (14.08.1941–14.12.2017)","authors":"A. Doroshenko, M. Kolosov, N. Mchedlov-Petrossyan, A. Korobov","doi":"10.26565/2220-637x-2021-37-01","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-37-01","url":null,"abstract":"","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42901089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-07DOI: 10.26565/2220-637x-2021-36-07
Pavel Efimov, Andrey V. Kramarenko, V. Tomak
We have considered the dependences of the specific (κ) and molar (Λ) electrical conductivity (EC) of aqueous electrolyte solutions on the molar concentration and temperature for sulfates of divalent metals (Mn, Co, Ni, Cu, Zn, Cd) in a wide concentration range at 5 – 35°C. To describe such systems we propose a modified cubic equation (MCE): κ = C∙c3k + Q∙c2k + L∙ck, where C, Q, L, k are empirical parameters, fixed parameter k = 0.5 has been considered as well. From the correlation between the calculated parameters we assume that two of them are sufficient. The maximum of specific EC (κm) and the corresponding concentration (cm) have been calculated. We also assume that the systems under study are isomorphic in the normalized coordinates (κ/κm via c/cm). For the dependences like κ = A∙cx + B∙cy it is shown that x = 1 is a good approximation over the generalized sample. Empirical dependences with y = 5/4 and y = 4/3 are also considered. It is shown that they give comparable results to MCE. The proposed approach is tested on EC data of aqueous solutions of some salts. Similar two-parameter κ(κm, cm; c) equations of other authors have been considered. In order to describe the dependence of the specific EC on temperature and concentration we propose an equation κ = (A25 + a∙θ)∙c – (B25 + b∙θ)∙c5/4, where θ is the reduced temperature and A25, a, B25 and b are empirical parameters. Also a generalized equation for the molar EC of concentrated electrolyte solutions is proposed: Λ(Λ*, Λm, cm; c), where Λ* is the effective limiting molar EC, and Λm is the molar EC at c = cm. It was found that Λ* and Λm depend linearly on temperature. The average value of the exponent is close to 1/3, which brings the generalized molar EC equation closer to the equation derived from the quasi-lattice model of electrolyte solutions.
我们已经考虑了电解质水溶液的比电导率（κ）和摩尔电导率（∧）对二价金属（Mn、Co、Ni、Cu、Zn、Cd）硫酸盐在5–35°C的宽浓度范围内的摩尔浓度和温度的依赖性。为了描述这种系统，我们提出了一个修正的三次方程（MCE）：κ=c3k+Q∙c2k+L∙ck，其中C、Q、L、k是经验参数，固定参数k=0.5也被考虑在内。根据计算参数之间的相关性，我们假设其中两个参数就足够了。计算了比EC的最大值（κm）和相应的浓度（cm）。我们还假设所研究的系统在归一化坐标（κ/κm via c/cm）中是同构的。对于像κ=A∙cx+B∙cy这样的依赖性，表明x=1是广义样本上的一个很好的近似。还考虑了y=5/4和y=4/3的经验依赖性。结果表明，它们给出的结果与MCE相当。所提出的方法在某些盐的水溶液的EC数据上进行了测试。其他作者也考虑了类似的双参数κ（κm，cm；c）方程。为了描述特定EC对温度和浓度的依赖性，我们提出了一个方程κ=（A25+a∙θ）∙c–（B25+b∙θ）∙c5/4，其中θ是降低的温度，A25、a、B25和b是经验参数。此外，还提出了浓电解质溶液的摩尔EC的广义方程：∧（∧*，∧m，cm；c），其中∧*是有效极限摩尔EC，而∧m是c=cm时的摩尔EC。发现∧*和∧m与温度线性相关。指数的平均值接近1/3，这使得广义摩尔EC方程更接近于从电解质溶液的准晶格模型导出的方程。
{"title":"Concentration and temperature empirical relationships of the electrical conductivity of electrolyte solutions","authors":"Pavel Efimov, Andrey V. Kramarenko, V. Tomak","doi":"10.26565/2220-637x-2021-36-07","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-36-07","url":null,"abstract":"We have considered the dependences of the specific (κ) and molar (Λ) electrical conductivity (EC) of aqueous electrolyte solutions on the molar concentration and temperature for sulfates of divalent metals (Mn, Co, Ni, Cu, Zn, Cd) in a wide concentration range at 5 – 35°C. To describe such systems we propose a modified cubic equation (MCE): κ = C∙c3k + Q∙c2k + L∙ck, where C, Q, L, k are empirical parameters, fixed parameter k = 0.5 has been considered as well. From the correlation between the calculated parameters we assume that two of them are sufficient. The maximum of specific EC (κm) and the corresponding concentration (cm) have been calculated. We also assume that the systems under study are isomorphic in the normalized coordinates (κ/κm via c/cm). For the dependences like κ = A∙cx + B∙cy it is shown that x = 1 is a good approximation over the generalized sample. Empirical dependences with y = 5/4 and y = 4/3 are also considered. It is shown that they give comparable results to MCE.\u0000\u0000The proposed approach is tested on EC data of aqueous solutions of some salts. Similar two-parameter κ(κm, cm; c) equations of other authors have been considered. In order to describe the dependence of the specific EC on temperature and concentration we propose an equation κ = (A25 + a∙θ)∙c – (B25 + b∙θ)∙c5/4, where θ is the reduced temperature and A25, a, B25 and b are empirical parameters. Also a generalized equation for the molar EC of concentrated electrolyte solutions is proposed: Λ(Λ*, Λm, cm; c), where Λ* is the effective limiting molar EC, and Λm is the molar EC at c = cm. It was found that Λ* and Λm depend linearly on temperature. The average value of the exponent is close to 1/3, which brings the generalized molar EC equation closer to the equation derived from the quasi-lattice model of electrolyte solutions.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42897492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-29DOI: 10.26565/2220-637x-2021-36-06
V. Ivanov, Pavlo V. Trostianko, S. Kovalenko, Anastasia Volodchenko, T. Chernozhuk, Darya Stepaniuk, O. Kalugin
In order to develop approaches to predict the spectral properties of organic dyes for solar cells the test calculations of typical π-conjugated systems with various structural fragments, have been performed. Among the structural elements there are benzene, oxazole, oxsadiazole, thiophene and coumarin fragments. Nitro, methoxy, dimethylamino and diethylamino groups are substituents. According to the obtained experimental data, the diethylamino group at position 7 of the coumarin moiety gave the highest bato- and hyperchromic shifts of spectra. Experimental absorption spectra were measured in various solvents with different polarity. Among them are cyclohexane, dimethoxyethane, tetrahydrofuran, methanol, acetonitrile, and dimethylsulfoxide. It has been shown that there are no significant changes in the λ(max) absorption of coumarin-based compounds when the solvent is changed to a more polar one, but there is a noticeable tendency to increase the intensity of the absorption spectra. For the theoretical interpretations of electronic spectra absorption ab initio density functional theory (DFT) as well as semi-empirical methods (PPP/CIS, ZINDO/S, AM1/CIS) were used. In the DFT calculations the functionals B3LYP, CAM-B3LYP, M06-2x, PBE1PBE, wB97XD were used. A significant discrepancy in the estimations of electronic excitations is demonstrated by the DFT for the different functionals. It is concluded that DFT calculations should be performed by using both B3LYP and CAM-B3LYP (or M06-2x) functionals. Linear response theory has been used to evaluate the solvatochromic properties of π-conjugated compounds in the DFT frameworks. In general it was found that semi-empirical approaches especially π-electron method PPP/CIS and all valence method ZINDO/S can provide adequate estimations of excitation energies of π-conjugated dyes for moderate computer resources.
{"title":"Quantum-chemical calculations of electronic spectra absorption: ab initio or semiempirical methods?","authors":"V. Ivanov, Pavlo V. Trostianko, S. Kovalenko, Anastasia Volodchenko, T. Chernozhuk, Darya Stepaniuk, O. Kalugin","doi":"10.26565/2220-637x-2021-36-06","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-36-06","url":null,"abstract":"In order to develop approaches to predict the spectral properties of organic dyes for solar cells the test calculations of typical π-conjugated systems with various structural fragments, have been performed. Among the structural elements there are benzene, oxazole, oxsadiazole, thiophene and coumarin fragments. Nitro, methoxy, dimethylamino and diethylamino groups are substituents. According to the obtained experimental data, the diethylamino group at position 7 of the coumarin moiety gave the highest bato- and hyperchromic shifts of spectra. Experimental absorption spectra were measured in various solvents with different polarity. Among them are cyclohexane, dimethoxyethane, tetrahydrofuran, methanol, acetonitrile, and dimethylsulfoxide. It has been shown that there are no significant changes in the λ(max) absorption of coumarin-based compounds when the solvent is changed to a more polar one, but there is a noticeable tendency to increase the intensity of the absorption spectra. For the theoretical interpretations of electronic spectra absorption ab initio density functional theory (DFT) as well as semi-empirical methods (PPP/CIS, ZINDO/S, AM1/CIS) were used. In the DFT calculations the functionals B3LYP, CAM-B3LYP, M06-2x, PBE1PBE, wB97XD were used. A significant discrepancy in the estimations of electronic excitations is demonstrated by the DFT for the different functionals. It is concluded that DFT calculations should be performed by using both B3LYP and CAM-B3LYP (or M06-2x) functionals. Linear response theory has been used to evaluate the solvatochromic properties of π-conjugated compounds in the DFT frameworks. In general it was found that semi-empirical approaches especially π-electron method PPP/CIS and all valence method ZINDO/S can provide adequate estimations of excitation energies of π-conjugated dyes for moderate computer resources.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41994879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-17DOI: 10.26565/2220-637x-2021-36-05
E. Moskaeva, K. Ostrovskiy, S. Shekhovtsov, N. Mchedlov-Petrossyan
This paper is aimed to estimate the transmittance of the electronic effects in the fluorescein molecule between the phthalic acid residue and the xanthene moiety. Despite the almost orthogonal orientation of the latter with respect to the rest of the molecule, some influence of substituents in this 9-aryl ring on the dissociation of the hydroxyl group of the hydroxyxanthene cannot be ruled out. In order to reveal this (possible) effect, we blocked the carboxylic group via esterification. The reason of using dimethyl sulfoxide as solvent was the high Hammett’s “rho” constant for phenolic group. The pKa values of eight methyl or ethyl esters of 3'-, 4'-, and 5'-nitro and amino fluoresceins were determined in benzoate and salicylate buffer solutions using the spectrophotometric method. For nitro derivatives, the dissociation constants of the cationic forms of the dyes were also determined in diluted p-toluenesulfonic acid. The study reveals increasing in the pKa by 0.2–0.3 units in the case of amino derivatives, while the nitro group decreases the pKas by 0.2–0.8. Also, the position of the substituent is of importance; the 5'-substituents display the least influence. In addition, the pKa values of methyl and ethyl esters of eosin (2,4,5,7-tetrabromofluorescein) were determined in order to clarify the influence of the alkyl group. The absorption maxima and molar absorptivities of the anions, as well as the pKas in DMSO coincide within the margin of errors.
{"title":"Transmittance of electronic effects in the fluorescein molecule: nitro and amino groups in the phthalic acid residue","authors":"E. Moskaeva, K. Ostrovskiy, S. Shekhovtsov, N. Mchedlov-Petrossyan","doi":"10.26565/2220-637x-2021-36-05","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-36-05","url":null,"abstract":"This paper is aimed to estimate the transmittance of the electronic effects in the fluorescein molecule between the phthalic acid residue and the xanthene moiety. Despite the almost orthogonal orientation of the latter with respect to the rest of the molecule, some influence of substituents in this 9-aryl ring on the dissociation of the hydroxyl group of the hydroxyxanthene cannot be ruled out. In order to reveal this (possible) effect, we blocked the carboxylic group via esterification. The reason of using dimethyl sulfoxide as solvent was the high Hammett’s “rho” constant for phenolic group. The pKa values of eight methyl or ethyl esters of 3'-, 4'-, and 5'-nitro and amino fluoresceins were determined in benzoate and salicylate buffer solutions using the spectrophotometric method. For nitro derivatives, the dissociation constants of the cationic forms of the dyes were also determined in diluted\u0000p-toluenesulfonic acid. The study reveals increasing in the pKa by 0.2–0.3 units in the case of amino derivatives, while the nitro group decreases the pKas by 0.2–0.8. Also, the position of the substituent is of importance; the 5'-substituents display the least influence. In addition, the pKa values of methyl and ethyl esters of eosin (2,4,5,7-tetrabromofluorescein) were determined in order to clarify the influence of the alkyl group. The absorption maxima and molar absorptivities of the anions, as well as the pKas in DMSO coincide within the margin of errors.","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69002242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-11DOI: 10.26565/2220-637x-2021-36-04
V. Protsenko, D. Bogdanov, Tetyana Butyrina, F. Danilov
Kinetic characteristics of the nickel ion discharge were investigated for the first time from electrolytes based on a new kind of ionic liquids, deep eutectic solvents. The study was carried out using electrolytes based on ethaline, a liquid eutectic mixture of choline chloride choline and ethylene glycol in a molar ratio of 1:2, respectively, in which 1 М NiCl2·6H2O was dissolved. It was shown that the apparent transfer coefficients for electrochemical process in the system Ni(II)/Ni(0) in ethaline were equal to α=0.309 and β=0.255 for anodic and cathodic reactions, respec-tively. It is difficult to interpret these values in the framework of known criteria of consecutive electrochemical pro-cesses. In order to explain this phenomenon, a theoretical conception was used, that was earlier developed by Gileadi. According to that conception, electric charge during metal electrodeposition is transferred through the electrode interface by metal ions, but not by electrons. Therefore, potential barrier in a double electrical layer be-came very asymmetric (i.e. the apparent transfer coefficient deviates from 0.5). It was found that the introduction of TiO2 particles (0–10 g dm–3) into the electrolyte based on ethaline results in declaration of electrochemical re-duction of nickel (II) ions due to a partial blocking of the electrode surface by adsorbed colloidal particles of titani-um dioxide.
首次研究了基于新型离子液体——深共晶溶剂的电解质中镍离子放电的动力学特性。电解质为乙炔、氯化胆碱和乙二醇的液体共晶混合物，摩尔比分别为1:2，其中溶解1 М NiCl2·6H2O。结果表明，在乙炔中Ni(II)/Ni(0)体系中，电化学过程的表观传递系数分别为α=0.309和β=0.255。在连续电化学过程的已知标准框架中，很难解释这些值。为了解释这一现象，使用了一个理论概念，这个概念是由Gileadi早期提出的。根据这一概念，金属电沉积过程中的电荷是通过金属离子而不是电子通过电极界面传递的。因此，双电层中的势垒变得非常不对称(即表观传递系数偏离0.5)。研究发现，将TiO2颗粒(0-10 g dm-3)引入基于乙炔的电解液中，由于二氧化钛胶体颗粒吸附在电极表面的部分阻断，导致镍(II)离子的电化学还原。
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Pub Date : 2020-12-31DOI: 10.26565/2220-637x-2021-36-01
N. Mchedlov-Petrossyan
{"title":"Professor Ōsawa and the most beautiful molecule","authors":"N. Mchedlov-Petrossyan","doi":"10.26565/2220-637x-2021-36-01","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-36-01","url":null,"abstract":"","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43944163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-31DOI: 10.26565/2220-637x-2021-36-02
E. Ōsawa
{"title":"Fifty years after the idea of C60 molecule","authors":"E. Ōsawa","doi":"10.26565/2220-637x-2021-36-02","DOIUrl":"https://doi.org/10.26565/2220-637x-2021-36-02","url":null,"abstract":"","PeriodicalId":34181,"journal":{"name":"Visnik Kharkivs''kogo natsional''nogo universitetu Seriia ximiia","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49325921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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