Academic literature on the topic 'Tartrate complexes'
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Journal articles on the topic "Tartrate complexes"
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Potvin, Pierre G., and Benjamin G. Fieldhouse. "An NMR study of mixed, tartrate-containing TiIV complexes." Canadian Journal of Chemistry 73, no. 3 (March 1, 1995): 401–13. http://dx.doi.org/10.1139/v95-053.
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The reactions of amines and amino alcohols with diisopropyl or diethyl R,R- or S,S-tartrate and Ti(OiPr)4 were examined by 1H and 13C NMR to obtain and characterize nonfluxional complexes with the tartrate units in novel binding modes. The mildly acidic 8-hydroxyquinoline and N-phenyl-N-benzoylhydroxylamine selectively formed the products of a double OiPr substitution, Ti2(tartrate)2(ligand)2(OiPr)2, and the products of double tartrate substitution, Ti(ligand)2(OiPr)2, while 2,4-pentanedione formed only the latter Basic amino alkanols formed diastereomerically pure Ti2(tartrate)2(aminoalkoxide)(OiPr)3 species. N,N-Dimethyl-2-aminoethanol (Hdmae) also and uniquely formed monomeric Ti(tartrate)2(Hdmae)2 species that could be described as doubly zwitterionic. Secondary or tertiary amines formed triply C2-symmetric Ti3(tartrate)4(amine)2(OiPr)4 assemblies. Some minor components were believed to be μ-OiPr species. All mixed complexes except Ti(tartrate)2(Hdmae)2 contained chelating and bridging tartrate units, without coordination by ester carbonyls. A nonchelating, nonbridging tartrate unit was also present in the amino alcohol cases. Primary amines, aromatic amines, and hydrazines all failed to provide identifiable complexes. As well, N,N-dibenzylhydroxylamine failed to generate in solution the complex that had previously been characterized by X-ray crystallography. Amidst the rich chemistry of TiIV-tartrate systems, the evident selectivities in product formation were ascribed to macro-ring closures that are specifically directed by the electronic nature of the addend. Transient OiPr-bridged intermediates were also implicated. Keywords: mixed TiIV alkoxides, chiral TiIV alkoxides, enantiospecific complexation.
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Prananto, Yuniar Ponco, Rafi Dwiasis Wibisono, Sasti Gona Fadhilah, Rachmat Tjahjanto, Darjito, and Firsta Luthfiani Salsabila. "Crystallization of Mn(II) and Cd(II) Complexes in A Water-Methanol System: Tartrate vs Nicotinamide Ligand Selectivity." Acta Chimica Asiana 5, no. 1 (April 27, 2022): 166–72. http://dx.doi.org/10.29303/aca.v5i1.114.
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Ligand selectivity of tartrate vs nicotinamide in a water-methanol system has been observed in the crystallization of Mn(II) and Cd(II) complexes. These complexes were crystallized at room temperature by a layered solution technique using a water-methanol mixture solvent in a M(II):tartrate:nicotinamide (M = Mn, Cd) molar ratio of 1:1:2. Complexes of M(II)-nicotinamide and M(II)-tartrate were also prepared for data comparison. Analysis of the crystals by infrared spectroscopy, powder-X-ray diffraction and qualitative anion test showed that in a presence of both tartrate and nicotinamide, the Mn(II) forms neutral Mn(II)-tartrate hydrate complex, whereas the Cd(II) forms ionic Cd(II)-nicotinamide chloride complex. In the case of Mn(II) complex, tartrate tend to coordinate as ligand than the nicotinamide, although molar ratio of nicotinamide was doubled than that of tartrate ligand. In contrast, the neutral nicotinamide ligand is more predominant to coordinate in the Cd(II) complex than the anionic tartrate. The tartrate-nicotinamide ligand selectivity in the crystallization of Mn(II) and Cd(II) complexes is likely due to the use of tartrate salt as precursor and the choice of solvent mixture. In addition, powder-XRD analysis confirms that there was no indication of M(II)-tartrate and M(II)-nicotinamide that co-crystallized together at the same time by both metal ions.
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Bott, Raymond C., Graham Smith, Dalius S. Sagatys, Daniel E. Lynch, and Colin H. L. Kennard. "Group 15 Complexes with α-Hydroxy Carboxylic Acids: 7. The Preparation and Structure Determination of Sodium (+)-Tartrato Arsenate(III), [Na8As10(C4H2O6)8(C4H3O6)2(H2O)19]n; Silver(I) (+)-Tartrato Arsenate(III), [Ag9As10(C4H2O6)9(C4H3O6)(H4As2O5) (H2O)10]n and Rubidium Citrato Antimonate(III), [Rb2Sb4(C6H5O7)2(C6H6O7)2(C6H7O7)4(H2O)2]." Australian Journal of Chemistry 53, no. 12 (2000): 917. http://dx.doi.org/10.1071/ch00138.
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The structures of sodium (+)-tartrato arsenate(III),[Na8As10(C4H2O6)8(C4H3O6)2(H2O)19]n(1), silver (+)-tartrato arsenate(III),[Ag9As10(C4H2O6)9(C4H3O6)(H4As2O5)(H2O)10](2) and rubidium citrato antimonate(III)[Rb2Sb4(C6H6O7)6(C6H7O7)2(H2O)2](3) have been determined by X-ray methods and refined to residuals of 0.085(1), 0.072 (2) and 0.065 (3) for 5018, 4487 and 8207 observed reflections,respectively. The (+)-tartrato complexes (1) and (2) are similar instructure to the two known isomorphous silver(I) (+)-tartratoarsenate(III) complexes in that independent anionic[As2(tartrate)2] dimericcages are linked to the sodium or silver counter-cations, respectively,through free carboxyl oxygen atoms. However, the structures are made morecomplex by the presence of labile water molecules in the lattice, resulting insome disorder. Furthermore, charge balance in both (1) and (2) requires thepresence of two and one tri-negative tartrato units, respectively, among theten independent tartrate units in each structure, an unusual feature for Asand Sb complexes with this ligand species. Bond distances within the fivearsenic(III)-(+)-tartrate dimers in each structure are: As–O(hydroxy), 1.75(2)–1.84(2) Å (1); 1.75(3)–1.83(2) Å(2) and As–O (carboxy), 1.94(2)–2.13(3) Å (1);1.95(2)–2.14(2) Å (2). In addition, the structure of (2) has twoshort Ag–As bonds [2.500, 2.524(3) Å] in the terminalsites of two of the f ive independent dimers, as well as an additionalAg–As bond [2.613(4) Å] to an unusual dimeric arseniousacid residue(H4As2O5),part of an As2AgO3 hetero-ringforming the polymeric network structure. The antimony(III) citrate complex (3)is isomorphous and isostructural with the previously reported potassiumanalogue which involves mixed-valence citrato ligands in conventionalbis-chelate four-coordination about the antimony centres, linked by bothseven- and eight-coordinate rubidium ions [Rb–O,2.743(10)–3.102(9) Å]. The arsenic and antimony atoms in allcompounds have typical distorted pseudo-trigonal bipyramidal stereochemistry.
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Selvaraj, M., S. Thamotharan, Siddhartha Roy, and M. Vijayan. "X-ray studies of crystalline complexes involving amino acids and peptides. XLIV. Invariant features of supramolecular association and chiral effects in the complexes of arginine and lysine with tartaric acid." Acta Crystallographica Section B Structural Science 63, no. 3 (May 16, 2007): 459–68. http://dx.doi.org/10.1107/s010876810701107x.
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The tartaric acid complexes with arginine and lysine exhibit two stoichiometries depending upon the ionization state of the anion. The structures reported here are DL-argininium DL-hydrogen tartrate, bis(L-argininium) L-tartrate, bis(DL-lysinium) DL-tartrate monohydrate, L-lysinium D-hydrogen tartrate and L-lysinium L-hydrogen tartrate. During crystallization, L-lysine preferentially interacts with D-tartaric acid to form a complex when DL-tartaric acid is used in the experiment. The anions and the cations aggregate into separate alternating layers in four of the five complexes. In bis(L-argininium) L-tartrate, the amino acid layers are interconnected by individual tartrate ions which do not interact among themselves. The aggregation of argininium ions in the DL- and the L-arginine complexes is remarkably similar, which is in turn similar to those observed in other dicarboxylic acid complexes of arginine. Thus, argininium ions have a tendency to assume similar patterns of aggregation, which are largely unaffected by a change in the chemistry of partner molecules such as the introduction of hydroxyl groups or a change in chirality or stoichiometry. On the contrary, the lysinium ions exhibit fundamentally different aggregation patterns in the DL–DL complexes on the one hand and L–D and L–L complexes on the other. Interestingly, the pattern in the L–D complex is similar to that in the L–L complex. The lysinium ions in the DL–DL complex exhibit an aggregation pattern similar to those observed in the DL-lysine complexes involving other dicarboxylic acids. Thus, the effect of change in the chirality of a subset of the component complexes could be profound or marginal, in an unpredictable manner. The relevant crystal structures appear to indicate that the preference of L-lysine for D-tartaric acid is perhaps caused by chiral discrimination resulting from the amplification of a small energy difference.
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Bezryadin, S. G., V. V. Chevela, O. P. Ajsuvakova, V. Yu Ivanova, and D. V. Kuzyakin. "Titanium(iv) tartrate complexes in aqueous solutions." Russian Chemical Bulletin 64, no. 11 (November 2015): 2655–62. http://dx.doi.org/10.1007/s11172-015-1204-z.
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Spaether, Wolf, Gerhard Erker, Mathias Rump, Carl Krueger, and Joerg Kuhnigk. "Generation of Dinuclear Tartrate-Bridged Dicationic Titanocene Complexes." Organometallics 14, no. 6 (June 1995): 2621–23. http://dx.doi.org/10.1021/om00006a004.
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Todorovsky, D. S., M. M. Getsova, and M. M. Milanova. "Preparation and Characterization of Lanthanum‐Titanum Tartrate Complexes." Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry 33, no. 2 (January 6, 2003): 223–40. http://dx.doi.org/10.1081/sim-120017782.
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Jia, Yihong, Asma A. Alothman, Rui Liang, Xiaoyong Li, Weiyi Ouyang, Xiangdong Wang, Yong Wu, et al. "Oligomeric (Salen)Mn(III) Complexes Featuring Tartrate Linkers Immobilized over Layered Double Hydroxide for Catalytically Asymmetric Epoxidation of Unfunctionalized Olefins." Materials 13, no. 21 (October 29, 2020): 4860. http://dx.doi.org/10.3390/ma13214860.
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A series of oligomeric (salen)Mn(III) complexes featuring tartrate linkers were prepared and immobilized over layered double hydroxide, and then used as catalysts for asymmetric epoxidation of unfunctionalized olefins. Comprehensive characterizations including 1H NMR, FT-IR, UV-Vis, elemental analysis, GPC, and ICP-AES were used to illustrate structures of oligomeric (salen)Mn(III) complexes, while powdered XRD, nitrogen physisorption, together with XPS studies provided further details to detect structures of heterogeneous catalysts. Interestingly, scanning electron microscopy found an interesting morphology change during modification of layered supporting material. Catalytic experiments indicated that configuration of major epoxide products was determined by salen chirality more than that of tartrate linker, but enantioselectivity (e.e. values) could be enhanced when tartrate and salen showed identical chiral configurations. Furthermore, the (R,R)-salen moieties linked with (R,R)-tartrate spacers usually offered higher enantioselectivity compared to other combinations. Lastly, Zn(II)/Al(III) layered double hydroxide played as a rigid supporting material in catalysis, showing positive chiral induction and high recycling potential in catalytic reactions.
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Sakurai, Hiromu, Satoko Funakoshi, and Yusuke Adachi. "New developments of insulinomimetic dinuclear vanadyl(IV)-tartrate complexes." Pure and Applied Chemistry 77, no. 9 (January 1, 2005): 1629–40. http://dx.doi.org/10.1351/pac200577091629.
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The number of patients suffering from diabetes mellitus (DM) is increasing year by year throughout the world. In 2003, the world population was 6.3 billion, and the number of patients with DM in the adult population (20-79 years old) was 0.194 billion, which corresponded to 5.1 % of all disease incidence in that age range. In 2005, it is forecasted that the world population will increase to 8.0 billion and the ratio of DM to total disease incidence will increase to 6.3 %, with a disproportionate number of cases in Southeast Asia, the West Pacific, Central Asia, and North, Central, and South America. To treat Type 1 and Type 2 DM clinically, insulin preparations and synthetic drugs, respectively, have been used. However, these treatments are associated with some problems, such as several times of daily insulin injections following blood glucose monitoring and side effects in the case of the synthetic drugs. Consequently, a new class of therapeutic compounds is anticipated. After many trials, vanadium-containing complexes have been proposed to improve and treat both types of DM by in vivo experiments. We present an overview of insulinomimetic and antidiabetic vanadyl (+4 vanadium, V) complexes, and propose new candidates for dinuclear vanadyl complexes with naturally occurring ligands. The current state of research on the dinuclear vanadyl(IV)-tartrate complexes is described in regard to the physicochemical characteristics, in vitro insulinomimetic and in vivo blood-glucose-lowering effects of the prepared complexes.
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Tipton, Peter A., and Jack Peisach. "Pulsed EPR analysis of tartrate dehydrogenase active-site complexes." Biochemistry 30, no. 3 (January 1991): 739–44. http://dx.doi.org/10.1021/bi00217a024.
Full textDissertations / Theses on the topic "Tartrate complexes"
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Pileckienė, Jolanta. "Katodiniai procesai Cu(II) tartratinių kompleksų tirpaluose." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050613_185602-23753.
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Cathodic processes occurring in the solutions containing Cu(II) tartaric complexes have been investigated. The equations accounting for the material balance have been constructed and used for the estimation of distribution of complexes and ligands in the bulk of solution. It was established that dominating particles in acidic media (pH < 3) are: Cu2+ and tartaric complex CuL, tartaric acid LH2 and its anion LH-. Potentials of non-polarized copper electrodes were found to be reversible and to follow Nernst equation. According to the analysis performed, surface oxide Cu2O is not able to form in acidic (pH < 3) media.
Cathodic voltammograms obtained for the solutions of different acidity exhibit two characteristic current peaks arising from Cu(II) reduction and hydrogen evaluation. An analysis of voltammetric extrema shows that both processes are irreversible. Based on the regularities of the mass transport of chemically interacting substances, surface distribution of components has been simulated. These date were used for the transformation of experimental voltammograms into normalized Tafel plots. According to their analysis, the rate-controlling step of Cu(II) reduction is the transfer of the first electron onto Cu2+ aqua-complex. The values of kinetic parameters were found to be as follows: the cathodic charge transfer coefficient is equal to 0.33 and the exchange current density is equal to 50 mA cm-2.
An analysis of the second current peak leads to the conclusion... [to full text]
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Сьомкіна, Олена Володимирівна. "Удосконалення електрохімічного осадження функціональних покрить міддю на сплави заліза та алюмінію." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/39104.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.03 – технічна електрохімія. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р.
Дисертацію присвячено удосконаленню технологічного процесу нанесення функціональних мідних покриттів на вироби зі сплавів заліза й алюмінію, які використовуються для підвищення електро- та теплопровідності, забезпечення надійності контактних з'єднань, надання поверхні каталітичних властивостей. Досліджено кінетику і механізм відновлення гідроксотартратного комплексу міді. Встановлено, що катодний процес протікає в області змішаної кінетики і ускладнений хімічною стадією дисоціації комплексного іона. Розроблено склад електроліту міднення, що забезпечує осадження покриттів з міцною адгезією до більш електронегативної основи. Отриманий розчин екологічно безпечний та стійкий при тривалій експлуатації. Вивчено вплив параметрів електролізу (температури, густини струму, концентрації компонентів розчину) на морфологію і якість одержуваних покриттів. Встановлено, що для поліпшення зчеплення мідного осаду з виробами зі сплавів алюмінію, необхідно створити на їх поверхні оксидну плівку з розвиненою пористою поверхнею, що задається умовами формування. Виявлено корозійні і електричні характеристики сформованих оксидів. Визначено, що додавання активуючої домішки фторид-іону до електроліту міднення сприяє більш рівномірному розподілу металу по поверхні сплавів.Thesis for the degree of candidate of technical sciences in specialty 05.17.03 – technical electrochemistry. – National Technical University "Kharkov Polytechnic Institute", Kharkiv, 2018. The thesis is devoted to the improvement of the technological process of applying copper coatings to products made of alloys of iron and aluminum, which are intended for electrical purposes. The kinetics and mechanism of the reduction of the copper hydroxotartrate complex are studied. It is found that the cathodic process includes delayed stage of electron transfer and chemical dissociation stage of the complex ion. The composition of the electrolyte for copper deposition has been developed, which ensures the deposition of coatings with good adhesion to the electronegative base. The resulting solution is environmentally safe and stable for long-term use. The effect of electrolysis parameters on the morphology and quality of the coatings was studied. In order to improve the adhesion of the copper deposit to parts made of aluminum alloys, it is necessary to create an oxide film having a developed porous surface, which is specified by the conditions of its formation. The corrosion and electrical characteristics of the oxides formed are revealed. It is determined that the addition of the fluoride ion (as activating impurity to the electrolyte for copper plating) promotes a more even distribution of the metal over the surface of the alloys.
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Сьомкіна, Олена Володимирівна. "Удосконалення електрохімічного осадження функціональних покрить міддю на сплави заліза та алюмінію." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/39049.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.03 – технічна електрохімія. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018 р.
Дисертацію присвячено удосконаленню технологічного процесу нанесення функціональних мідних покриттів на вироби зі сплавів заліза й алюмінію, які використовуються для підвищення електро- та теплопровідності, забезпечення надійності контактних з'єднань, надання поверхні каталітичних властивостей. Досліджено кінетику і механізм відновлення гідроксотартратного комплексу міді. Встановлено, що катодний процес протікає в області змішаної кінетики і ускладнений хімічною стадією дисоціації комплексного іона. Розроблено склад електроліту міднення, що забезпечує осадження покриттів з міцною адгезією до більш електронегативної основи. Отриманий розчин екологічно безпечний та стійкий при тривалій експлуатації. Вивчено вплив параметрів електролізу (температури, густини струму, концентрації компонентів розчину) на морфологію і якість одержуваних покриттів. Встановлено, що для поліпшення зчеплення мідного осаду з виробами зі сплавів алюмінію, необхідно створити на їх поверхні оксидну плівку з розвиненою пористою поверхнею, що задається умовами формування. Виявлено корозійні і електричні характеристики сформованих оксидів. Визначено, що додавання активуючої домішки фторид-іону до електроліту міднення сприяє більш рівномірному розподілу металу по поверхні сплавів.Thesis for the degree of candidate of technical sciences in specialty 05.17.03 – technical electrochemistry. – National Technical University "Kharkov Polytechnic Institute", Kharkiv, 2018. The thesis is devoted to the improvement of the technological process of applying copper coatings to products made of alloys of iron and aluminum, which are intended for electrical purposes. The kinetics and mechanism of the reduction of the copper hydroxotartrate complex are studied. It is found that the cathodic process includes delayed stage of electron transfer and chemical dissociation stage of the complex ion. The composition of the electrolyte for copper deposition has been developed, which ensures the deposition of coatings with good adhesion to the electronegative base. The resulting solution is environmentally safe and stable for long-term use. The effect of electrolysis parameters on the morphology and quality of the coatings was studied. In order to improve the adhesion of the copper deposit to parts made of aluminum alloys, it is necessary to create an oxide film having a developed porous surface, which is specified by the conditions of its formation. The corrosion and electrical characteristics of the oxides formed are revealed. It is determined that the addition of the fluoride ion (as activating impurity to the electrolyte for copper plating) promotes a more even distribution of the metal over the surface of the alloys.
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Wang, Lei. "Photodegradation of organic pollutants induced by Fe(III)-caoxylate complexes in aqueous solution." Clermont-Ferrand 2, 2008. https://tel.archives-ouvertes.fr/tel-00728829.
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La photodégradation de l'herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de son principal photoproduit (2,4-DCP) en présence de trois complexes Fe(III)-carboxylate (citrate, pyruvate, tartrate) a été étudiée. Les rendements quantiques de disparition du 2,4-D augmentent dans cet ordre : Fe(III)-TAr < Fe(III)-Cit < Fe(OH)2+ < Fe(III)-Pyr. Le même mécanisme de dégradation du 2,4-D est observé pour les trois complexes de fer et correspond à celui déjà décrit avec des processus généraux de radicaux hydroxyle. Le 2,4-D est dégradé sélectivement en 2,4-DCP, qui après formation de différents photoproduits peut être minéralisé complètement en H2O, Cl- et CO2. La formation de radicaux hydroxyles, obtenue sous irradiation des solutions de complexes Fe(III)-carboxylate a été confirmée par spectroscopie RPE. Ce travail montre que la présence de complexes Fe(III)-carboxylate peut avoir un impact considérable sur le devenir de polluants organiques présents dans les compartiments aquatiques naturels
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Wang, Lei. "Photodégradation de pollutants organiques induite par des complexes Fe(III)-carboxylate en solutions aqueuses." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00728829.
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La photodégradation de l'herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de son principal photoproduit (2,4-DCP) en présence de trois complexes Fe(III)-carboxylate (citrate, pyruvate, tartrate) a été étudiée. Les rendements quantiques de disparition du 2,4-D augmentent dans cet ordre : Fe(III)-TAr < Fe(III)-Cit < Fe(OH)2+ < Fe(III)-Pyr. Le même mécanisme de dégradation du 2,4-D est observé pour les trois complexes de fer et correspond à celui déjà décrit avec des processus généraux de radicaux hydroxyle. Le 2,4-D est dégradé sélectivement en 2,4-DCP, qui après formation de différents photoproduits peut être minéralisé complètement en H2O, Cl- et CO2. La formation de radicaux hydroxyles, obtenue sous irradiation des solutions de complexes Fe(III)-carboxylate a été confirmée par spectroscopie RPE. Ce travail montre que la présence de complexes Fe(III)-carboxylate peut avoir un impact considérable sur le devenir de polluants organiques présents dans les compartiments aquatiques naturels.
Book chapters on the topic "Tartrate complexes"
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Orešková, Gabriela, Lukáš Krivosudský, Ján Šimunek, and Jozef Noga. "Structural and spectral properties of tartrato complexes of vanadium(V) from quantum chemical calculations." In Péter R. Surján, 123–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-49825-5_15.
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E. Coleman, Robert, Alexei A. Stuchebrukhov, and Roger B. Boulton. "The Kinetics of Autoxidation in Wine." In Recent Advances in Chemical Kinetics [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103828.
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The kinetics of autoxidation in wine begins with Fenton (1876) who observed that tartaric acid could be oxidized in the presence of iron without peroxide if left in air. Rodopulo (1951) demonstrated that iron tartrate complexes added to wine promoted more extensive oxygen consumption than the molar equivalent of inorganic ferrous or ferric salts. The role of iron complexes in the activation of oxygen, the formation of reactive oxygen species and the initiation of autoxidation are crucial for understanding wine oxidation kinetics. Mechanisms based on hydroxyl radicals versus the ferryl species are likely to have different oxidation products of wine components based on pH effects. The ferryl ion, hydroxyl radical, and tartaric acid radical are proposed as key intermediates in the proposed general mechanism for hydrogen peroxide formation and the autoxidation of wine components. A quantitative kinetic description is presented for the autoxidation of tartaric acid and extended to other acid components as potential ligands. This chapter explores the theoretical considerations of iron complexes formation, oxygen activation, an autoxidative mechanism, and experimental measurements of tartaric acid oxidation as the basis of autoxidation in wine.
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Taber, Douglass F. "The Nicolaou Synthesis of (+)-Hirsutellone B." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0089.
Full textAbstract:
(+)-Hirsutellone B 3, isolated from the insect pathogenic fungus Hirsutella nivea BCC 2594, shows good activity (MIC = 0.78 μg/mL) against Mycobacterium tuberculosis. Approaching the synthesis of 3, K. C. Nicolaou of Scripps/La Jolla envisioned and reduced to practice (Angew. Chem. Int. Ed. 2009, 49, 6870) a spectacular tandem intramolecular epoxide opening: internal Diels-Alder cyclization (1 2) that established all three of the carbocyclic rings of 3 with the proper relative and absolute configuration. The construction of 1 began with commercial ( R) -(+)-citronellal 4. Wittig homologation established the ( Z )-iodide 5. Selective ozonolysis followed by condensation with the phosphorane 7 set the stage for Jørgensen-Córdova (Tetrahedron Lett. 2006, 47, 99) epoxidation with H2O2 and a catalytic amount of the Hayashi catalyst 9. Condensation of 10 with the phosphorane 11 followed by Cu-catalyzed coupling of 12 with the organostannane 13 completed the assembly of 1. This approach underscores the strategic advantages of the Jørgensen-Córdova epoxidation over the Sharpless protocol. It is not necessary to reduce the aldehyde to the allyic alcohol, then reoxidize. Furthermore, the Jørgensen-Córdova epoxidation, using catalytic 9, is operationally easier than the Sharpless procedure, which often uses stoichiometric amounts of tartrate ester. The cyclization of 1 proceeded by way of 13, with the newly formed stereogenic center having the diene equatorial on the cyclohexane. Endo cycloaddition catalyzed by the Lewis acid in the solution then gave 2. The facility with which the cyclization of 13 set both the substituents and the stereogenic centers of 2 raises the possibility that the biosynthesis might also follow such an internal [4 + 2] cycloaddition. To complete the synthesis of 3, it was necessary to construct the strained paracyclophane. The authors took advantage of the facile cyclization of the thiolate liberated from 18, then installed the ring-contracted alkene with a Ramburg-Bäcklund rearrangement of 19. They completed the synthesis of (+)-hirsutellone B 3 by exposing the ketone 21 to NH3 in CH3OH/H2O.
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Taber, Douglass. "The Roush Synthesis of ( + )-Superstolide A." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0093.
Full textAbstract:
( + )-Superstolide A 3, isolated from the New Caledonian sponge Neosiphonia superstes, shows interesting cytotoxicity against malignant cell lines at ~ 4 ng/mL concentration. The key transformation in the synthesis of 3 described (J. Am. Chem. Soc. 2008, 130, 2722) by William R. Roush of Scripps Florida was the transannular Diels-Alder cyclization of 2, which established, in one step with high diastereocontrol, both the cis decalin and the macrolactone of 3. The octaene 1 was assembled from four stereodefined fragments. The first, the linchpin 6, was prepared from the stannyl aldehyde 4. Homologation gave the enyne 5, which on hydroboration and oxidation gave 6. Earlier, Professor Roush had optimized the crotylation of the protected alaninal 7. In this case, the Brown reagent 8 delivered the desired Felkin product 9. Protection followed by ozonolysis gave the aldehyde 10. Crotylation with the Roush-developed tartrate 11 then gave the alkene 12, setting the stage for conversion to the iodide 13. Coupling of 13 with 6 completed the preparation of 14. The third component of (+)-superstolide A 3, the phosphonium salt 21, was assembled by Brown allylation of the aldehyde 15, to give 17. Protecting group interchange followed by ozonolysis delivered 18, which via Still-Gennari homologation was carried on to 21. Condensation with the fourth component, the aldehyde 22 , and esterification with 14 then gave 1. Under high dilution Suzuki conditions 1 was converted to 2. Storage in CDCl3 for five days, or brief warming, cyclized 2 to a single diastereomer of the transannular Diels-Alder product, that was carried on to (+)-superstolide A 3. While acyclic trienes comparable to 2 could be induced to cyclize, the transannular Diels-Alder reaction proceeded with much higher diastereocontrol.
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Taber, Douglass F. "The Qin Synthesis of (+)-Gelsemine." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0093.
Full textAbstract:
(+)-Gelsemine 3 has no particular biological activity, but its intricate architecture continues to inspire the ingenuity of organic synthesis chemists. Yong Qin of Sichuan University devised (Angew. Chem. Int. Ed. 2012, 51, 4909) an enantiospecific synthesis of 3, a key step of which was the cyclization of 1 to 2. The starting material for the synthesis was the inexpensive diethyl tartrate 4, which was converted over six steps into the N-sulfonyl aziridine 5. The addition of 6 was highly regioselective, leading, after N-methylation, to the alkyne 7. After alcohol protection, the sulfonyl group was smoothly removed by sonication with Mg powder in methanol. Addition to acryonitrile then gave 8. Semihydrogenation of 8 set the stage for construction of the lactone 1. The anion of 1, generated by exposure to LDA, cyclized to 2 with significant diastereoselectivity. The lactone of 2 was selectively reduced with Dibal, to give an aldehyde that was protected as the acetal. The exposed primary alcohol was then oxidized to the aldehyde 9. Condensation of 9 with the enolate of 10 followed by dehydration delivered the alkene 11, with the stage set for a second intramolecular nitrile anion addition. In the event, the cyclization of 11 delivered 12, the wrong diastereomer. This was corrected by selenation and oxidation to give an alkene, which was hydrogenated to 13. Exposure to acid deprotected both the MOM group of 13 and the acetal, then promoted cyclization to 14. Reduction of the nitrile to the aldehyde followed by methylenation completed the synthesis of (+)-gelsemine 3. It should be noted that the hydrogenation to form 13 had to be carried out carefully to avoid premature removal of the N-methoxy group. That group was critical for the successful conversion of 13 to 14.
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Taber, Douglass. "Alkaloid Synthesis: (-)-Aurantioclavine (Stoltz), (-)-Esermethole (Nakao/Hiyama/ Ogoshi), (-)-Kainic Acid (Tomooka), Dasycarpidone (Bennasar), (-)-Cephalotaxine (Ishibashi) and Lysergic Acid (Fujii/Ohno)." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0060.
Full textAbstract:
Intriguing strategies have been developed for the stereocontrolled assembly of complex alkaloid structures. Brian M. Stoltz of Caltech prepared (J. Am. Chem. Soc. 2008, 130, 13745) the enantiomerically-pure alcohol precursor to the secondary amine 1 by enantioselective oxidation of the racemic alcohol. Intramolecular Mitsunobu coupling of 1 then led to (-)-Aurantioclavine 3. Yoshiaki Nakao and Tamejiro Hiyama of Kyoto University and Sensuke Ogoshi of Osaka University developed (J. Am. Chem. Soc. 2008, 130, 12874) an enantioselective Ni catalyst for the cyclization of 4 to 5. Oxidation and cyclization then delivered (-)-Esermethole 6. Although the sulfonamide 7 appears to be prochiral, in fact its two most stable conformations are bent, and enantiomers of each other, with a significant barrier for interconversion. Katsuhiko Tomooka of Kyushu University separated (Tetrahedron Lett. 2008, 49, 6327) the enantiomers of 7, then carried the enantiomercially-pure 7 on, by Pd-catalyzed Cope rearrangement, to 8 and so to (-)-Kainic Acid 9. M.-Lluïsa Bennasar of the University of Barcelona prepared (J. Org. Chem. 2008, 73, 9033) the acyl selenide 11 from the indole 10. While the radical derived from 11 might have been expected to undergo 5-exo cyclization, in the event the 6-endo mode dominated, to give Dasycarpidone 12 and its diastereomer. Hiroyuki Ishibashi of Kanazawa University showed (Organic Lett. 2008, 10, 4129) that the radical cascade cyclization of the enamine 13, derived from diethyl tartrate, proceeded with remarkable diastereocontrol, to give 14. The amide 14 was converted to (-)-Cephalotaxine 15. Nobutaka Fujii and Hiroaki Ohno, also of Kyoto University, used (Organic Lett. 2008, 10, 5239) a Pd catalyst to mediate the cascade cyclization of 16 to 17. Although 16 has two stereogenic centers, including the allene, it is the aminated stereogenic center of 17 that sets the absolute configuration of the product Lysergic Acid 18. One intermediate in the conversion of 16 to the tetracyclic 17 is the tricyclic π-allyl Pd complex. If all the material could be channeled through that pathway, there is a good chance that the chiral Trost catalyst could effectively control the absolute configuration of the aminated stereogenic center as it is formed, leading to the enantiomerically enriched product 18.
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Taber, Douglass. "The Kozmin Synthesis of Spirofungin A." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0089.
Full textAbstract:
Often, 6,6-spiroketals such as Spirofungin A 3 have a strong anomeric bias. Spirofungin A does not, as the epimer favored by double anomeric stabilization suffers from destabilizing steric interactions. In his synthesis of 3, Sergey A. Kozmin of the University of Chicago took advantage (Angew. Chem. Int. Ed. 2007, 46, 8854) of the normally-destablizing spatial proximity of the two alkyl branches of 3, joining them with a siloxy linker to assure the anomeric preference of the spiroketal. The assembly of 1 showcased the power of asymmetric crotylation, and of Professor Kozmin’s linchpin cyclopropenone ketal cross metathesis. To achieve the syn relative (and absolute) configuration of 6, commercial cis-2-butene was metalated, then condensed with the Brown (+)-MeOB(Ipc)2 auxiliary. The accompanying Supporting Information, accessible via the online HTML version of the journal article, includes a succinct but detailed procedure for carrying out this homologation. For the anti relative (and absolute) configuration of 9, it is more convenient to use the tartrate 8 introduced by Roush. Driven by the release of the ring strain inherent in 10, ring opening cross metathesis with 6 proceeded to give the 1:1 adduct 11 in near quantitative yield. The derived cross-linked silyl ether 12 underwent smooth ring-closing metathesis to the dienone 1. On hydogenation, the now-flexible ring system could fold into the spiro ketal. With the primary and secondary alcohols bridged by the linking silyl ether, only one anomeric form, 2, of the spiro ketal was energetically accessible. A remaining challenge was the stereocontrolled construction of the trisubstituted alkene. To this end, the aldehyde 13 was homologated to the dibromide 14. Pd-mediated coupling of the alkenyl stannane 15 with 14 was selective for the E bromide. The residual Z bromide was then coupled with Zn(CH3)2 to give 16. These steps, and the final steps to complete the construction of spirofungin A 3 , could be carried out without exposure to equilibrating acid, so the carefully established spiro ketal confi guration was maintained.