Maja Biocic, Deni Karabatić, Dea Tomić, Lea Kukoc-Modun
{"title":"Spectrophotometric Determination of N-acetyl-L-Cysteine in Pharmaceutical Formulations by Flow Injection and Sequential Injection Analysis: Comparison of the Methods","authors":"Maja Biocic, Deni Karabatić, Dea Tomić, Lea Kukoc-Modun","doi":"10.5562/cca4016","DOIUrl":"https://doi.org/10.5562/cca4016","url":null,"abstract":"","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134884727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vanja Radolić, Goran Šmit, Igor Miklavčić, Marina Poje Sovilj
: Adsorption of radon in the air was investigated on hematite, α -Fe 2 O 3 , and charcoal activated powder. Hematite had almost doubled efficiency in comparison to charcoal activated powder in the same experimental conditions but over a significantly longer per iod. Adsorption isotherms revealed a typical Langmuir shape on hematite and almost linear on activated charcoal. Linear models of Langmuir, Freundlich and Dubinin-Radushkevich isotherms showed that radon adsorption on both adsorbents is a favourable chemical process, with stronger interactions on hematite, that takes place forming a monolayer of ads orbed radon. The kinetic analysis confirmed forming of a monolayer on both adsorbents and two rate-controlling steps during radon adsorption on hematite, instead of one on activated charcoal, which could be considered as a reason of slower rate of process on hematite .
{"title":"Comparison of Radon Adsorption on Hematite and Charcoal Activated Powder in Air","authors":"Vanja Radolić, Goran Šmit, Igor Miklavčić, Marina Poje Sovilj","doi":"10.5562/cca4013","DOIUrl":"https://doi.org/10.5562/cca4013","url":null,"abstract":": Adsorption of radon in the air was investigated on hematite, α -Fe 2 O 3 , and charcoal activated powder. Hematite had almost doubled efficiency in comparison to charcoal activated powder in the same experimental conditions but over a significantly longer per iod. Adsorption isotherms revealed a typical Langmuir shape on hematite and almost linear on activated charcoal. Linear models of Langmuir, Freundlich and Dubinin-Radushkevich isotherms showed that radon adsorption on both adsorbents is a favourable chemical process, with stronger interactions on hematite, that takes place forming a monolayer of ads orbed radon. The kinetic analysis confirmed forming of a monolayer on both adsorbents and two rate-controlling steps during radon adsorption on hematite, instead of one on activated charcoal, which could be considered as a reason of slower rate of process on hematite .","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135448259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Namık Özdemir, Rukiye Fırıncı, Muhammet Emin Günay
: A new [Cu 4 OCl 6 L 4 ] cluster [L = 1 -(allyl)-1 H -imidazole] has been isolated and its crystal structure and spectroscopic properties determined. The compound crystallizes as a yellow solid in the monoclinic system, space group P 2 1 , with cell constants a = 10.6937(7) Å, b = 13.1004(7) Å, c = 13.2452(9) Å, β = 93.537(6)°, and two formula units per cell. The title tetranuclear complex has a central µ 4 - oxide ion surrounded tetrahedrally by four Cu II atoms. Each Cu atom is connected to three others via bridging Cl atoms. The fifth coordination position, located on the central Cu─O axis on the outside of the cluster, is occupied by an N atom of the monodentate imidazole ligand. The resulting coordi nation geometry of the metal ion is a slightly distorted trigonal bipyramid with the O and N atoms in the axial positions. Th e molecular structure and spectroscopic data were obtained using density functional theory (DFT/HSEH1PBE) method with the cc - pVDZ basis set for C, H, N, O and Cl atoms, and the LANL2DZ basis set for the Cu atoms, and compared with the experimental data. Consequently, the exp erimental data well coherences with the theoretical ones.
{"title":"Synthesis, Experimental and Theoretical Characterization of (μ4-oxo)hexakis(μ2-chloro)-tetrakis[1-(allyl)-1H-imidazole]tetracopper(II)","authors":"Namık Özdemir, Rukiye Fırıncı, Muhammet Emin Günay","doi":"10.5562/cca3933","DOIUrl":"https://doi.org/10.5562/cca3933","url":null,"abstract":": A new [Cu 4 OCl 6 L 4 ] cluster [L = 1 -(allyl)-1 H -imidazole] has been isolated and its crystal structure and spectroscopic properties determined. The compound crystallizes as a yellow solid in the monoclinic system, space group P 2 1 , with cell constants a = 10.6937(7) Å, b = 13.1004(7) Å, c = 13.2452(9) Å, β = 93.537(6)°, and two formula units per cell. The title tetranuclear complex has a central µ 4 - oxide ion surrounded tetrahedrally by four Cu II atoms. Each Cu atom is connected to three others via bridging Cl atoms. The fifth coordination position, located on the central Cu─O axis on the outside of the cluster, is occupied by an N atom of the monodentate imidazole ligand. The resulting coordi nation geometry of the metal ion is a slightly distorted trigonal bipyramid with the O and N atoms in the axial positions. Th e molecular structure and spectroscopic data were obtained using density functional theory (DFT/HSEH1PBE) method with the cc - pVDZ basis set for C, H, N, O and Cl atoms, and the LANL2DZ basis set for the Cu atoms, and compared with the experimental data. Consequently, the exp erimental data well coherences with the theoretical ones.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135989432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Hernández, G. Álvarez-Romero, M. Rivera, Simplicio González-Montiel, C. H. Rios-Reyes, L. Mendoza-Huizar
: In the present work, the influence of the concentration of bitartrate ions (HT) on the copper electrodeposition process was analyzed. The study was carried out from an aqueous solution containing 0.001 M of CuX (where X = (NO 3– ) 2 ,(Cl – ) 2 , S O 4 2– ) and x M KHT (where x = 0.005 M, 0.01 M, and 0.015 M). From voltammetric and chronoamperometric studies, the results indicate that copper electrodeposition is a diffusion-controlled process. The current density transients were well described through a kinetic me chanism involving capacitive and faradaic contributions. The diffusion coefficient values of Cu 1+ and Cu 2+ result to be similar at the different concentration values of potassium bitartrate used in this work.
本文分析了酒石酸盐离子（HT）浓度对铜电沉积过程的影响。该研究是在含有0.001 M CuX（其中X=（NO3-）2、（Cl-）2、S O 4 2-）和X M KHT（其中X=0.005 M、0.01 M和0.015 M）的水溶液中进行的。从伏安法和计时电流法的研究结果表明，铜电沉积是一个扩散控制的过程。通过涉及电容和法拉第贡献的动力学机制，很好地描述了电流密度瞬态。在本工作中使用的酒石酸钾的不同浓度值下，Cu1+和Cu2+的扩散系数值相似。
{"title":"Influence of Bitartrate Ion Concentration in the Copper Electrodeposition Onto a Polycrystalline Gold Electrode","authors":"M. Hernández, G. Álvarez-Romero, M. Rivera, Simplicio González-Montiel, C. H. Rios-Reyes, L. Mendoza-Huizar","doi":"10.5562/cca3757","DOIUrl":"https://doi.org/10.5562/cca3757","url":null,"abstract":": In the present work, the influence of the concentration of bitartrate ions (HT) on the copper electrodeposition process was analyzed. The study was carried out from an aqueous solution containing 0.001 M of CuX (where X = (NO 3– ) 2 ,(Cl – ) 2 , S O 4 2– ) and x M KHT (where x = 0.005 M, 0.01 M, and 0.015 M). From voltammetric and chronoamperometric studies, the results indicate that copper electrodeposition is a diffusion-controlled process. The current density transients were well described through a kinetic me chanism involving capacitive and faradaic contributions. The diffusion coefficient values of Cu 1+ and Cu 2+ result to be similar at the different concentration values of potassium bitartrate used in this work.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"1 1","pages":""},"PeriodicalIF":0.3,"publicationDate":"2021-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44838490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cate S. Anstöter, N. Bašić, P. Fowler, T. Pisanski
Catacondensed benzenoids (those benzenoids having no carbon atom belonging to three hexagonal rings) form the simplest class of polycyclic aromatic hydrocarbons (PAH). They have a long history of study and are of wide chemical importance. In this paper, mathematical possibilities for natural extension of the notion of a catacondensed benzenoid are discussed, leading under plausible chemically and physically motivated restrictions to the notion of a catacondensed chemical hexagonal complex (CCHC). A general polygonal complex is a topological structure composed of polygons that are glued together along certain edges. A polygonal complex is flat if none of its edges belong to more than two polygons. A connected flat polygonal complex determines an orientable or nonorientable surface, possibly with boundary. A CCHC is then a connected flat polygonal complex all of whose polygons are hexagons and each of whose vertices belongs to at most two hexagonal faces. We prove that all CCHC are Kekulean and give formulas for counting the perfect matchings in a series of examples based on expansion of cubic graphs in which the edges are replaced by linear polyacenes of equal length. As a preliminary assessment of the likely stability of molecules with CCHC structure, all-electron quantum chemical calculations are applied to molecular structures based on several CCHC, using either linear or kinked unbranched catafused polyacenes as the expansion motif. The systems examined all have closed shells according to Huckel theory and all correspond to minima on the potential surface, thus passing the most basic test for plausibility as a chemical species.
{"title":"Catacondensed Chemical Hexagonal Complexes: A Natural Generalisation of Benzenoids","authors":"Cate S. Anstöter, N. Bašić, P. Fowler, T. Pisanski","doi":"10.5562/cca3765","DOIUrl":"https://doi.org/10.5562/cca3765","url":null,"abstract":"Catacondensed benzenoids (those benzenoids having no carbon atom belonging to three hexagonal rings) form the simplest class of polycyclic aromatic hydrocarbons (PAH). They have a long history of study and are of wide chemical importance. In this paper, mathematical possibilities for natural extension of the notion of a catacondensed benzenoid are discussed, leading under plausible chemically and physically motivated restrictions to the notion of a catacondensed chemical hexagonal complex (CCHC). A general polygonal complex is a topological structure composed of polygons that are glued together along certain edges. A polygonal complex is flat if none of its edges belong to more than two polygons. A connected flat polygonal complex determines an orientable or nonorientable surface, possibly with boundary. A CCHC is then a connected flat polygonal complex all of whose polygons are hexagons and each of whose vertices belongs to at most two hexagonal faces. We prove that all CCHC are Kekulean and give formulas for counting the perfect matchings in a series of examples based on expansion of cubic graphs in which the edges are replaced by linear polyacenes of equal length. As a preliminary assessment of the likely stability of molecules with CCHC structure, all-electron quantum chemical calculations are applied to molecular structures based on several CCHC, using either linear or kinked unbranched catafused polyacenes as the expansion motif. The systems examined all have closed shells according to Huckel theory and all correspond to minima on the potential surface, thus passing the most basic test for plausibility as a chemical species.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2021-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47506122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The imino tautomers of isocytosine were objects of investigation at the TD-DFT level of theory TD BLYP/6-311++G(d,p). We studied the mechanisms of the H1-N detachment in these tautomers through excited-state reaction paths. It was proposed that these transformations occur through the 1πσ* excited-state reaction paths of the imino tautomers. The mechanisms involve dissociations of the N1–H bonds in the tautomers and lead to crossings between the reaction paths of 1πσ* and S0 electronic states. One can suppose that such processes would facilitate the tautomerizations of the imino tautomers if further mechanisms have been found.
{"title":"Photo-induced Dissociation of the N1–H Bond in the Imino Tautomers of Isocytosine in Water Medium","authors":"B. H. Dimitrov, V. Delchev","doi":"10.5562/cca3659","DOIUrl":"https://doi.org/10.5562/cca3659","url":null,"abstract":"The imino tautomers of isocytosine were objects of investigation at the TD-DFT level of theory TD BLYP/6-311++G(d,p). We studied the mechanisms of the H1-N detachment in these tautomers through excited-state reaction paths. It was proposed that these transformations occur through the 1πσ* excited-state reaction paths of the imino tautomers. The mechanisms involve dissociations of the N1–H bonds in the tautomers and lead to crossings between the reaction paths of 1πσ* and S0 electronic states. One can suppose that such processes would facilitate the tautomerizations of the imino tautomers if further mechanisms have been found.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3659","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48453049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rotational barrier around the phenyl-formyl bond between the minimum and transition states of para-substituted benzaldehydes was computationally studied for 34 electron-donating substituents. The rotational barrier exhibited very good correlation with shortening of the phenyl-formyl bond, lengthening of carbonyl bond, increase of electron density at the formyl group, increase of stabilization energy, lowering of chemical shift in the 13C NMR of the formyl carbon, and with the values of empirical Hammett σp+ constants. Therefore, rotational barrier is a useful quantum mechanical parameter for quantifying the electron-donating substituent effect and π-conjugation in parasubstituted benzaldehydes. Based upon the rotational barrier a scale has been set in this work to judge the electron donating effect of substituents. Moreover, a canonical structure has been proposed for stronger electron-donating substituents. The results of this study reveal that simultaneous presence of electron acceptor formyl group and electron-donating groups is mandatory for the extension of resonance stabilization.
{"title":"Rotational Barrier and Quantification of Electron-Donating Substituent Effects: a Computational Study of para-Substituted Benzaldehydes","authors":"Ali Hussain Yateem","doi":"10.5562/cca3672","DOIUrl":"https://doi.org/10.5562/cca3672","url":null,"abstract":"The rotational barrier around the phenyl-formyl bond between the minimum and transition states of para-substituted benzaldehydes was computationally studied for 34 electron-donating substituents. The rotational barrier exhibited very good correlation with shortening of the phenyl-formyl bond, lengthening of carbonyl bond, increase of electron density at the formyl group, increase of stabilization energy, lowering of chemical shift in the 13C NMR of the formyl carbon, and with the values of empirical Hammett σp+ constants. Therefore, rotational barrier is a useful quantum mechanical parameter for quantifying the electron-donating substituent effect and π-conjugation in parasubstituted benzaldehydes. Based upon the rotational barrier a scale has been set in this work to judge the electron donating effect of substituents. Moreover, a canonical structure has been proposed for stronger electron-donating substituents. The results of this study reveal that simultaneous presence of electron acceptor formyl group and electron-donating groups is mandatory for the extension of resonance stabilization.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"93 1","pages":"85-95"},"PeriodicalIF":0.3,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3672","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47152829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present study aims to discuss the data on levels and distribution of rare earth elements, including Y, (REYs) in leaves of three different citrus species (lemon, orange, and tangerine) and provide additional information about the major, minor and trace elements in two biological certified reference materials (CRMs), Apple leave (NIST SRM 1515) and Rye grass (ERM CD281). In all samples, element concentrations were determined by High Resolution Inductively Coupled Plasma Mass Spectrometry. The obtained data display substantial variability in the distribution of REY elements, not only between different citrus species but also between different genera of plants indicating their different uptake and accumulation abilities. Measured concentrations of REYs in citrus leaves were substantially lower compared to the literature values, although the fractionation indices were comparable. The data for CRMs provide additional information for the 14 elements in NIST SRM 1515 and the 30 elements in ERM CD281, including rare earth elements.
{"title":"Distribution of Rare Earth Elements in Citrus Leaves and Reference Materials (NIST SRM 1515 and ERM CD281)","authors":"Ž. Fiket, Martina Furdek Turk","doi":"10.5562/cca3663","DOIUrl":"https://doi.org/10.5562/cca3663","url":null,"abstract":"The present study aims to discuss the data on levels and distribution of rare earth elements, including Y, (REYs) in leaves of three different citrus species (lemon, orange, and tangerine) and provide additional information about the major, minor and trace elements in two biological certified reference materials (CRMs), Apple leave (NIST SRM 1515) and Rye grass (ERM CD281). In all samples, element concentrations were determined by High Resolution Inductively Coupled Plasma Mass Spectrometry. The obtained data display substantial variability in the distribution of REY elements, not only between different citrus species but also between different genera of plants indicating their different uptake and accumulation abilities. Measured concentrations of REYs in citrus leaves were substantially lower compared to the literature values, although the fractionation indices were comparable. The data for CRMs provide additional information for the 14 elements in NIST SRM 1515 and the 30 elements in ERM CD281, including rare earth elements.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47848027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Karthika, R. Praveena, S. Ramachandran, K. Sadasivam, G. Salgado, P. Muñoz, Lorena A. Gerli, L. Mendoza-Huizar
: Electronic structure calculations were performed to analyze the effectiveness of linking agents (sulfur and nitrogen) in connecting the trans-azobenzene sandwiched between two gold surfaces (Au-atoms). It was analyzed the dynamics of the load carrier and the electronic structure of the molecular backbone by applying an external electric field (EF ), also a detailed structural, frontier orbital and natural bond orbital analysis (NBO) were performed. From the NBO analysis, it was possible to predict the path of charge flow in the molecular system. Electrostatic potential mapping allowed us to visualize the charge redistribution in the molecular system caused by the EF application. Our results indicate that when the nitrogen atom is used as a linking agent, the
{"title":"A DFT Study on the Efficacy of Linking Agents (Sulfur and Nitrogen) to Connect Trans-azobenzene Sandwiched Between Two Gold Electrodes","authors":"C. Karthika, R. Praveena, S. Ramachandran, K. Sadasivam, G. Salgado, P. Muñoz, Lorena A. Gerli, L. Mendoza-Huizar","doi":"10.5562/CCA3695","DOIUrl":"https://doi.org/10.5562/CCA3695","url":null,"abstract":": Electronic structure calculations were performed to analyze the effectiveness of linking agents (sulfur and nitrogen) in connecting the trans-azobenzene sandwiched between two gold surfaces (Au-atoms). It was analyzed the dynamics of the load carrier and the electronic structure of the molecular backbone by applying an external electric field (EF ), also a detailed structural, frontier orbital and natural bond orbital analysis (NBO) were performed. From the NBO analysis, it was possible to predict the path of charge flow in the molecular system. Electrostatic potential mapping allowed us to visualize the charge redistribution in the molecular system caused by the EF application. Our results indicate that when the nitrogen atom is used as a linking agent, the","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49245102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：