S. Musić, M. Marciuš, S. Krehula, S. Popović, E. Kuzmann, Z. Homonnay
Zinc borosilicate glass with optimized chemical composition was synthesized and doped with 5 wt % α-Fe2O3. XRD, 57Fe Mössbauer, FT-IR, UV/Vis/NIR and FE SEM were used as the characterization methods. XRD showed the amorphous nature of the samples synthesized. 57Fe Mössbauer spectra confirmed the superposition of Fe3+ in tetrahedral and Fe2+ in octahedral positions. FT-IR spectra showed general features characteristic of different borosilicate glasses. The NIR band at 1116 nm in the UV/Vis/NIR spectrum was assigned to the Fe2+ transition, whereas the Fe3+ transition bands could not be assigned due to the overlapping of several spectral bands of different origin in the UV region centered at 282 nm and the Vis region between 415 to 496 nm. Zinc borosilicate glass as synthesized can be considered as a possible matrix in the immobilization of nonradioactive as well as radioactive wastes.
{"title":"Some Microstructural Properties of Zinc Borosilicate Glass as a Possible Matrix in the Immobilization of Various Wastes","authors":"S. Musić, M. Marciuš, S. Krehula, S. Popović, E. Kuzmann, Z. Homonnay","doi":"10.5562/cca3574","DOIUrl":"https://doi.org/10.5562/cca3574","url":null,"abstract":"Zinc borosilicate glass with optimized chemical composition was synthesized and doped with 5 wt % α-Fe2O3. XRD, 57Fe Mössbauer, FT-IR, UV/Vis/NIR and FE SEM were used as the characterization methods. XRD showed the amorphous nature of the samples synthesized. 57Fe Mössbauer spectra confirmed the superposition of Fe3+ in tetrahedral and Fe2+ in octahedral positions. FT-IR spectra showed general features characteristic of different borosilicate glasses. The NIR band at 1116 nm in the UV/Vis/NIR spectrum was assigned to the Fe2+ transition, whereas the Fe3+ transition bands could not be assigned due to the overlapping of several spectral bands of different origin in the UV region centered at 282 nm and the Vis region between 415 to 496 nm. Zinc borosilicate glass as synthesized can be considered as a possible matrix in the immobilization of nonradioactive as well as radioactive wastes.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3574","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48916124","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}
B. Ramalingeswara Rao, Mohana Rao Katiki, Dileep Kommula, S. Narayanan, R. J. Anto, M. Murty
The synthesis of a series of substituted hippuric acid (2-benzamidoacetic acid) derivatives containing arylsulfonylpiperazine nucleus (3a–j, 4a–j) is described. The compounds were synthesized by coupling hippuric/4-fluorohippuric acid with various arylsulfonylpiperazines using N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDCI). The structures of all the new compounds were confirmed by IR, NMR and MS spectral data. All the synthesized compounds have been evaluated for their in vitro cytotoxicity towards five human cancer cell lines of different origins viz. HeLa (Cervical), A549 (Lung), A375 (Skin), MD-AMB-231(Breast) and T98G (brain) and their IC50 values were determined. Among the compounds tested, 3b, 3d, 3g, 4c and 4e displayed significant cytotoxic activity (IC50 = 24.2–38.2 µM). T98G was the most sensitive cell line towards the compounds studied followed by HeLa, A375, A549 and MD-AMB-231.
{"title":"Synthesis of Novel Benzamide- piperazine-sulfonamide Hybrids as Potential Anticancer Agents","authors":"B. Ramalingeswara Rao, Mohana Rao Katiki, Dileep Kommula, S. Narayanan, R. J. Anto, M. Murty","doi":"10.5562/cca3535","DOIUrl":"https://doi.org/10.5562/cca3535","url":null,"abstract":"The synthesis of a series of substituted hippuric acid (2-benzamidoacetic acid) derivatives containing arylsulfonylpiperazine nucleus (3a–j, 4a–j) is described. The compounds were synthesized by coupling hippuric/4-fluorohippuric acid with various arylsulfonylpiperazines using N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDCI). The structures of all the new compounds were confirmed by IR, NMR and MS spectral data. All the synthesized compounds have been evaluated for their in vitro cytotoxicity towards five human cancer cell lines of different origins viz. HeLa (Cervical), A549 (Lung), A375 (Skin), MD-AMB-231(Breast) and T98G (brain) and their IC50 values were determined. Among the compounds tested, 3b, 3d, 3g, 4c and 4e displayed significant cytotoxic activity (IC50 = 24.2–38.2 µM). T98G was the most sensitive cell line towards the compounds studied followed by HeLa, A375, A549 and MD-AMB-231.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3535","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49331772","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}
Vasiliki Pardali, Erofili Giannakopoulou, Athina Konstantinidi, A. Kolocouris, Grigoris Zoidis
In this report we review our results on the development of 1,2-annulated adamantane heterocyclic derivatives and we discuss the structure-activity relationships obtained from their biological evaluation against influenza A virus. We have designed and synthesized numerous potent 1,2-annulated adamantane analogues of amantadine and rimantadine against influenza A targeting M2 protein the last 20 years. For their synthesis we utilized the key intermediates 2-(2-oxoadamantan-1-yl)acetic acid and 3-(2-oxoadamantan-1-yl)propanoic acid, which were obtained by a simple, fast and efficient synthetic protocol. The latter involved the treatment of protoadamantanone with different electrophiles and a carbon-skeleton rearrangement. These ketoesters offered a new pathway to the synthesis of 1,2-disubstituted adamantanes, which constitute starting materials for many molecules with pharmacological potential, such as the 1,2-annulated adamantane heterocyclic derivatives. To obtain additional insight for their binding to M2 protein three structurally similar 1,2-annulated adamantane piperidines, differing in nitrogen position, were studied using molecular dynamics (MD) simulations in palmitoyl-oleoyl-phosphatidyl-choline (POPC) hydrated bilayers.
{"title":"1,2-Αnnulated Adamantane Heterocyclic Derivatives as Anti-Influenza Α Virus Agents","authors":"Vasiliki Pardali, Erofili Giannakopoulou, Athina Konstantinidi, A. Kolocouris, Grigoris Zoidis","doi":"10.5562/cca3540","DOIUrl":"https://doi.org/10.5562/cca3540","url":null,"abstract":"In this report we review our results on the development of 1,2-annulated adamantane heterocyclic derivatives and we discuss the structure-activity relationships obtained from their biological evaluation against influenza A virus. We have designed and synthesized numerous potent 1,2-annulated adamantane analogues of amantadine and rimantadine against influenza A targeting M2 protein the last 20 years. For their synthesis we utilized the key intermediates 2-(2-oxoadamantan-1-yl)acetic acid and 3-(2-oxoadamantan-1-yl)propanoic acid, which were obtained by a simple, fast and efficient synthetic protocol. The latter involved the treatment of protoadamantanone with different electrophiles and a carbon-skeleton rearrangement. These ketoesters offered a new pathway to the synthesis of 1,2-disubstituted adamantanes, which constitute starting materials for many molecules with pharmacological potential, such as the 1,2-annulated adamantane heterocyclic derivatives. To obtain additional insight for their binding to M2 protein three structurally similar 1,2-annulated adamantane piperidines, differing in nitrogen position, were studied using molecular dynamics (MD) simulations in palmitoyl-oleoyl-phosphatidyl-choline (POPC) hydrated bilayers.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3540","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48712813","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}
Jelena Parlov Vuković, P. Novak, Tomislav Jednačak
Asphaltenes are the most polar oil components with molecular weights between 500 and 1000 Da, which primarily consist of carbons and hydrogens, some heteroatoms, such as nitrogen, sulphur, oxygen and traces of nickel, vanadium and iron. Owing to their extreme complexity, it is almost impossible to completely identify all the compounds present in asphaltene samples. Various analytical techniques and approaches were used to characterize asphaltenes but their structure and composition are still a matter of thorough investigations. NMR spectroscopy can reveal useful information on asphaltene molecular architecture and aggregation process. In that respect, one- and two-dimensional NMR techniques have widely been employed. Although NMR spectra of these complex mixtures are difficult to interpret, they still can provide valuable data, especially in combination with statistical methods. Some distinctive examples of using NMR spectroscopy to study asphaltenes are given in this review.
{"title":"NMR Spectroscopy as a Tool for Studying Asphaltene Composition","authors":"Jelena Parlov Vuković, P. Novak, Tomislav Jednačak","doi":"10.5562/cca3543","DOIUrl":"https://doi.org/10.5562/cca3543","url":null,"abstract":"Asphaltenes are the most polar oil components with molecular weights between 500 and 1000 Da, which primarily consist of carbons and hydrogens, some heteroatoms, such as nitrogen, sulphur, oxygen and traces of nickel, vanadium and iron. Owing to their extreme complexity, it is almost impossible to completely identify all the compounds present in asphaltene samples. Various analytical techniques and approaches were used to characterize asphaltenes but their structure and composition are still a matter of thorough investigations. NMR spectroscopy can reveal useful information on asphaltene molecular architecture and aggregation process. In that respect, one- and two-dimensional NMR techniques have widely been employed. Although NMR spectra of these complex mixtures are difficult to interpret, they still can provide valuable data, especially in combination with statistical methods. Some distinctive examples of using NMR spectroscopy to study asphaltenes are given in this review.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3543","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42729161","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}
Ring opening of 2-(chloromethyl)oxirane via the nucleophilic substitution with bromide and acetate anions was investigated using density functional theory (DFT) calculations. It was shown that the geometry of the transition states and the activation parameters of the reactions correspond to those of SN2-like mechanism. The nature of localized transition states was analyzed using More O’Ferrall – Jencks plots. The quantum chemical simulations of the potential energy surface for the ring-opening reaction of oxirane by nucleophiles confirmed the theoretical assumptions about the favored path of interactions, which is a backside α-attack of nucleophile. The effect of alkali metal cation (Li+, Na+, K+) on that path was estimated. It was found that the electrophilic activation with alkali metal cation is more pronounced in the reaction of 2-(chloromethyl)oxirane with dissociated ions, than with ionic pairs.
{"title":"A Computational Study of 2-(chloromethyl)oxirane Ring Opening by Bromide and Acetate Anions Considering Electrophilic Activation with Cations of Alkali Metals","authors":"K. Yutilova, Yuliia Bespal’ko, E. Shved","doi":"10.5562/CCA3505","DOIUrl":"https://doi.org/10.5562/CCA3505","url":null,"abstract":"Ring opening of 2-(chloromethyl)oxirane via the nucleophilic substitution with bromide and acetate anions was investigated using density functional theory (DFT) calculations. It was shown that the geometry of the transition states and the activation parameters of the reactions correspond to those of SN2-like mechanism. The nature of localized transition states was analyzed using More O’Ferrall – Jencks plots. The quantum chemical simulations of the potential energy surface for the ring-opening reaction of oxirane by nucleophiles confirmed the theoretical assumptions about the favored path of interactions, which is a backside α-attack of nucleophile. The effect of alkali metal cation (Li+, Na+, K+) on that path was estimated. It was found that the electrophilic activation with alkali metal cation is more pronounced in the reaction of 2-(chloromethyl)oxirane with dissociated ions, than with ionic pairs.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/CCA3505","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45077170","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}
This work reports a new selective and accurate multiresidue procedure for determination of 25 pesticides in red wine by GC-MS. Proposed procedure uses an original approach in sample preparation technique based on QuEChERS theory. Main focus of method development was modification of salts thus increasing ionic strength of solution which improved pesticides partitioning and extraction efficiency. LOQs were in the range 0.01–250 μg L–1 with 56 % of target pesticides below or equal to 10 μg L–1. RSD for most pesticides was < 20 % and recoveries were in the range 70–120 %. Matrix effect was found to be high for five pesticides confirming sample preparation procedure to be efficient. The proposed procedure was applied to 12 wine samples of different variety with determination of 40 % of target pesticides. Developed GC-MS methodology provides novel, selective and accurate approach for determination of 25 pesticide residues in red wine.
{"title":"GC-MS Modified Quechers Method for Multiresidue Pesticide Determination in Red Wine","authors":"Maja Pelajić, I. Pelajić, D. Pavlović, D. V. Čepo","doi":"10.5562/cca3552","DOIUrl":"https://doi.org/10.5562/cca3552","url":null,"abstract":"This work reports a new selective and accurate multiresidue procedure for determination of 25 pesticides in red wine by GC-MS. Proposed procedure uses an original approach in sample preparation technique based on QuEChERS theory. Main focus of method development was modification of salts thus increasing ionic strength of solution which improved pesticides partitioning and extraction efficiency. LOQs were in the range 0.01–250 μg L–1 with 56 % of target pesticides below or equal to 10 μg L–1. RSD for most pesticides was < 20 % and recoveries were in the range 70–120 %. Matrix effect was found to be high for five pesticides confirming sample preparation procedure to be efficient. The proposed procedure was applied to 12 wine samples of different variety with determination of 40 % of target pesticides. Developed GC-MS methodology provides novel, selective and accurate approach for determination of 25 pesticide residues in red wine.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3552","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48507275","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 article sheds light on some historical crossings of organic chemistry and chemical crystallography. It connects past and present bringing into the focus Prof. Kata Mlinarić-Majerski’s research. An impact of structural chemistry on organic synthesis and reactivity is shown. X-ray structure analysis was established as a unique method to determine the composition and architecture of synthetic and natural organic molecules, already in the second decade of the last century; some of historical and scientific milestones are shown. Numerous controversies were solved, when intriguing molecular structures had been determined and the nature of chemical bond was clarified. An absolute structure (chirality) determination using an anomalous dispersion of X-rays was an important step forward, particularly in pharmaceutical industry. Structural data provided by X-ray crystallography, stored by Cambridge Structural Data Centre have been of great impact on many areas of science. They are closely related to intra- and intermolecular forces and structure/function correlations directing us to synthesis of compounds with designed properties. The developments of supramolecular chemistry, crystal engineering, materials science, and most of all of molecular machines have been assisted by chemical crystallography. The essay does not aim to review the complete scientific opus of Prof. K. Mlinarić-Majerski but it is focused on some of the highlights of her research. The interdisciplinary approach in her research is related to the use of X-ray structural analysis to define molecular architecture, conformational chirality, conformational isomerism, and get insight into reaction paths, interactions governing molecular assembling, and to recognise chemical properties of new compounds. In these researches the X-ray crystallographers were involved.
{"title":"A Strong Link Between Organic Chemistry and Chemical Crystallography Started a Century Ago","authors":"B. Kojić-Prodić, K. Molčanov","doi":"10.5562/cca3534","DOIUrl":"https://doi.org/10.5562/cca3534","url":null,"abstract":"The article sheds light on some historical crossings of organic chemistry and chemical crystallography. It connects past and present bringing into the focus Prof. Kata Mlinarić-Majerski’s research. An impact of structural chemistry on organic synthesis and reactivity is shown. X-ray structure analysis was established as a unique method to determine the composition and architecture of synthetic and natural organic molecules, already in the second decade of the last century; some of historical and scientific milestones are shown. Numerous controversies were solved, when intriguing molecular structures had been determined and the nature of chemical bond was clarified. An absolute structure (chirality) determination using an anomalous dispersion of X-rays was an important step forward, particularly in pharmaceutical industry. Structural data provided by X-ray crystallography, stored by Cambridge Structural Data Centre have been of great impact on many areas of science. They are closely related to intra- and intermolecular forces and structure/function correlations directing us to synthesis of compounds with designed properties. The developments of supramolecular chemistry, crystal engineering, materials science, and most of all of molecular machines have been assisted by chemical crystallography. The essay does not aim to review the complete scientific opus of Prof. K. Mlinarić-Majerski but it is focused on some of the highlights of her research. The interdisciplinary approach in her research is related to the use of X-ray structural analysis to define molecular architecture, conformational chirality, conformational isomerism, and get insight into reaction paths, interactions governing molecular assembling, and to recognise chemical properties of new compounds. In these researches the X-ray crystallographers were involved.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3534","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43853792","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}
We used a combination of MD simulations and DFT calculations to reveal the precise chemical mechanism underlying the conversion of boronated nucleosides to natural nucleosides in the presence of hydrogen peroxide, which was recently experimentally demonstrated by Morihiro and Obika et al. (Chem. Sci. 2018, 9, 1112). Our results show that this process is initiated by the H2O2 deprotonation to a base concerted with the nucleophilic attack of the resulting OOH– anion onto the boron atom as the rate-limiting step of the overall transformation. This liberates a free base, followed by the 1,2-rearrangement to the C–OOH– adduct. Lastly, breaking of the O–O bond within the peroxide moiety cleaves the boron–carbon bond, giving boronic acid ester and the matching ketone as the final products. The obtained reaction profiles successfully interpret a much higher conversion rate of the thymine derivative over its guanine analogue, and rationalize why t-Bu-hydroperoxide is hindering the conversion, thus placing both aspects in firm agreement with experiments. The offered insight represents a promising tool for the future synthetic approaches of stimuli-responsive biomolecules, especially chemically caged prodrug-type nucleic acid therapeutics, bearing significant importance due to their application potential in diagnostics and therapy of various genetic disorders.
{"title":"From Hydrogen Peroxide-Responsive Boronated Nucleosides Towards Antisense Therapeutics – A Computational Mechanistic Study","authors":"Tana Tandarić, L. Hok, R. Vianello","doi":"10.5562/cca3592","DOIUrl":"https://doi.org/10.5562/cca3592","url":null,"abstract":"We used a combination of MD simulations and DFT calculations to reveal the precise chemical mechanism underlying the conversion of boronated nucleosides to natural nucleosides in the presence of hydrogen peroxide, which was recently experimentally demonstrated by Morihiro and Obika et al. (Chem. Sci. 2018, 9, 1112). Our results show that this process is initiated by the H2O2 deprotonation to a base concerted with the nucleophilic attack of the resulting OOH– anion onto the boron atom as the rate-limiting step of the overall transformation. This liberates a free base, followed by the 1,2-rearrangement to the C–OOH– adduct. Lastly, breaking of the O–O bond within the peroxide moiety cleaves the boron–carbon bond, giving boronic acid ester and the matching ketone as the final products. The obtained reaction profiles successfully interpret a much higher conversion rate of the thymine derivative over its guanine analogue, and rationalize why t-Bu-hydroperoxide is hindering the conversion, thus placing both aspects in firm agreement with experiments. The offered insight represents a promising tool for the future synthetic approaches of stimuli-responsive biomolecules, especially chemically caged prodrug-type nucleic acid therapeutics, bearing significant importance due to their application potential in diagnostics and therapy of various genetic disorders.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3592","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46954320","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}
Quantum-chemical calculations of cycloaddition properties of cyclic heterodienes substituted with guanidine functionality were carried out. Molecular and electronic structures of series of dienes (pyrrole, furan, thiophene, isoindole and 1,3-butadiene) were calculated and reactivity order established on the basis of FMO theory. Transition state calculations of model [4+2] cycloaddition reaction with acetylene indicate that guanidine substitution influences reaction barriers in moderate extent (up to ~4 kcal mol–1). The substitution position plays an important role on the sign and magnitude of the effect and protonation of nitrogen possessing substituents increases reactivity of dienes.
{"title":"Computational Study of Electronic Influence of Guanidine Substitution on Diels-Alder Reactions of Heterocyclic Dienes","authors":"I. Antol, Luka Barešić, Z. Glasovac, D. Margetić","doi":"10.5562/cca3570","DOIUrl":"https://doi.org/10.5562/cca3570","url":null,"abstract":"Quantum-chemical calculations of cycloaddition properties of cyclic heterodienes substituted with guanidine functionality were carried out. Molecular and electronic structures of series of dienes (pyrrole, furan, thiophene, isoindole and 1,3-butadiene) were calculated and reactivity order established on the basis of FMO theory. Transition state calculations of model [4+2] cycloaddition reaction with acetylene indicate that guanidine substitution influences reaction barriers in moderate extent (up to ~4 kcal mol–1). The substitution position plays an important role on the sign and magnitude of the effect and protonation of nitrogen possessing substituents increases reactivity of dienes.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":" ","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3570","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46079345","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}
Four novel salts of chloranilic acid (H2CA; 3,6-dichloro-2,5-dihydroxy-1,4-quinone) with organic cations pyridinium (Hpy+), piperazinediium (H2ppz2+), 4,4'-bipyridinediium (H2bpy2+) and 1,10-phenanthrolinium (Hphen+) were prepared and structurally characterised: (Hpy)2CA (1), (H2ppz)CA (2), (H2bpy)CA·4H2O (3) and (Hphen)HCA·MeOH (4). Supramolecular architecture is based on extensive hydrogen bonding and π-stacking. The central motive is chloranilate dianion which acts as an acceptor of two bifurcated hydrogen bonds. Topology and dimensionality of hydrogen bonded networks can be tuned by use of different cations: thus discrete motives, 1D chains and 2D layers were observed. Three different types of π-stacks are present: aromatic stacks, quinoid stacks and stacks of alternating quinoid and aromatic rings.
{"title":"Supramolecular Architecture of Chloranilate Salts with Organic Cations","authors":"K. Molčanov, M. Jurić, Lidija Androš Dubraja","doi":"10.5562/cca3537","DOIUrl":"https://doi.org/10.5562/cca3537","url":null,"abstract":"Four novel salts of chloranilic acid (H2CA; 3,6-dichloro-2,5-dihydroxy-1,4-quinone) with organic cations pyridinium (Hpy+), piperazinediium (H2ppz2+), 4,4'-bipyridinediium (H2bpy2+) and 1,10-phenanthrolinium (Hphen+) were prepared and structurally characterised: (Hpy)2CA (1), (H2ppz)CA (2), (H2bpy)CA·4H2O (3) and (Hphen)HCA·MeOH (4). Supramolecular architecture is based on extensive hydrogen bonding and π-stacking. The central motive is chloranilate dianion which acts as an acceptor of two bifurcated hydrogen bonds. Topology and dimensionality of hydrogen bonded networks can be tuned by use of different cations: thus discrete motives, 1D chains and 2D layers were observed. Three different types of π-stacks are present: aromatic stacks, quinoid stacks and stacks of alternating quinoid and aromatic rings.","PeriodicalId":10822,"journal":{"name":"Croatica Chemica Acta","volume":"34 11","pages":""},"PeriodicalIF":0.3,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.5562/cca3537","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41309353","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}
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