Literatura académica sobre el tema "Chimical reactivity"
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Artículos de revistas sobre el tema "Chimical reactivity"
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Verrier, Charlie, Sébastien Carret y Jean-François Poisson. "Ynol Ethers: Synthesis and Reactivity". CHIMIA International Journal for Chemistry 70, n.º 1 (24 de febrero de 2016): 93–96. http://dx.doi.org/10.2533/chimia.2016.93.
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Grimmel, Stephanie A. y Markus Reiher. "On the Predictive Power of Chemical Concepts". CHIMIA International Journal for Chemistry 75, n.º 4 (28 de abril de 2021): 311–18. http://dx.doi.org/10.2533/chimia.2021.311.
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Many chemical concepts can be well defined in the context of quantum chemical theories. Examples are the electronegativity scale of Mulliken and Jaffé and the hard and soft acids and bases concept of Pearson. The sound theoretical basis allows for a systematic definition of such concepts. However, while they are often used to describe and compare chemical processes in terms of reactivity, their predictive power remains unclear. In this work, we elaborate on the predictive potential of chemical reactivity concepts, which can be crucial for autonomous reaction exploration protocols to guide them by first-principles heuristics that exploit these concepts.
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Togni, Antonio. "70 Years Ferrocene!" CHIMIA International Journal for Chemistry 75, n.º 9 (15 de septiembre de 2021): 805–6. http://dx.doi.org/10.2533/chimia.2021.805.
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Some of the most important features of ferrocene chemistry – structure, reactivity, redox properties, and applications – are presented. Their value in the context of conveying many fundamental aspects of molecular chemistry is considered.
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Monkcom, Emily C., Pradip Ghosh, Emma Folkertsma, Hidde A. Negenman, Martin Lutz y Robertus J. M. Klein Gebbink. "Bioinspired Non-Heme Iron Complexes: The Evolution of Facial N, N, O Ligand Design". CHIMIA International Journal for Chemistry 74, n.º 6 (24 de junio de 2020): 450–66. http://dx.doi.org/10.2533/chimia.2020.450.
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Iron-containing metalloenzymes that contain the 2-His-1-Carboxylate facial triad at their active site are well known for their ability to activate molecular oxygen and catalyse a broad range of oxidative transformations. Many of these reactions are synthetically challenging, and developing small molecular iron-based catalysts that can achieve similar reactivity and selectivity remains a long-standing goal in homogeneous catalysis. This review focuses on the development of bioinspired facial N,N,O ligands that model the 2-His-1-Carboxylate facial triad to a greater degree of structural accuracy than many of the polydentate N-donor ligands commonly used in this field. By developing robust, well-defined N,N,O facial ligands, an increased understanding could be gained of the factors governing enzymatic reactivity and selectivity.
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Catalán, Silvia, Sócrates B. Munoz y Santos Fustero. "Unique Reactivity of Fluorinated Molecules with Transition Metals". CHIMIA International Journal for Chemistry 68, n.º 6 (26 de junio de 2014): 382–409. http://dx.doi.org/10.2533/chimia.2014.382.
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Shetaya, Waleed H. y Jen-How Huang. "Reactivity of Soil Mercury by Stable Isotope Dilution". CHIMIA International Journal for Chemistry 74, n.º 1 (26 de febrero de 2020): 58. http://dx.doi.org/10.2533/chimia.2020.58.
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Nóvoa, Luis, Laura Trulli, Alejandro Parra y Mariola Tortosa. "Copper, Boron and Vinyl Epoxides: from 1,4-Diols to Cyclopropylboronates". CHIMIA International Journal for Chemistry 74, n.º 11 (25 de noviembre de 2020): 852–56. http://dx.doi.org/10.2533/chimia.2020.852.
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Herein we describe the reactivity found between vinyl epoxides and catalytically generated copper-boryl complexes. By tuning the substituents of the alkene and/or the reaction conditions, 1,4-diols, allylic alcohols or cyclopropylboronates can be prepared. The stereochemical information of the vinyl epoxide is transferred to the products with high levels of stereocontrol.
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Jorner, Kjell. "Putting Chemical Knowledge to Work in Machine Learning for Reactivity". CHIMIA 77, n.º 1/2 (22 de febrero de 2023): 22. http://dx.doi.org/10.2533/chimia.2023.22.
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Machine learning has been used to study chemical reactivity for a long time in fields such as physical organic chemistry, chemometrics and cheminformatics. Recent advances in computer science have resulted in deep neural networks that can learn directly from the molecular structure. Neural networks are a good choice when large amounts of data are available. However, many datasets in chemistry are small, and models utilizing chemical knowledge are required for good performance. Adding chemical knowledge can be achieved either by adding more information about the molecules or by adjusting the model architecture itself. The current method of choice for adding more information is descriptors based on computed quantum-chemical properties. Exciting new research directions show that it is possible to augment deep learning with such descriptors for better performance in the low-data regime. To modify the models, differentiable programming enables seamless merging of neural networks with mathematical models from chemistry and physics. The resulting methods are also more data-efficient and make better predictions for molecules that are different from the initial dataset on which they were trained. Application of these chemistry-informed machine learning methods promise to accelerate research in fields such as drug design, materials design, catalysis and reactivity.
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Meyet, Jordan, Mark A. Newton, Jeroen A. van Bokhoven y Christophe Copéret. "Molecular Approach to Generate Cu(II) Sites on Silica for the Selective Partial Oxidation of Methane". CHIMIA International Journal for Chemistry 74, n.º 4 (29 de abril de 2020): 237–40. http://dx.doi.org/10.2533/chimia.2020.237.
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The selective partial oxidation of methane to methanol remains a great challenge in the field of catalysis. Cu-exchanged zeolites are promising materials, directly and selectively converting methane to methanol with high yield under cyclic conditions. However, the economic viability of these aluminosilicate materials for potential industrial applications remains a challenge. Exploring copper supported on non-microporous oxide supports and rationalising the structure/reactivity relationships extends the scope of material investigation and opens new possibilities. Recently, copper on alumina was demonstrated to be active and selective for the partial oxidation of methane. This work aims to explore the formation of well-defined Cu(II) oxo species on silica via surface organometallic chemistry and examines their reactivity for the selective transformation of methane to methanol. Isolated Cu(II) sites were generated via grafting of a tailored molecular precursor. Activation under oxidative conditions and subsequent removal of organic moieties from the grafted copper centres led to the formation of small copper (II) oxide clusters, which are active in the partial oxidation of methane under mild conditions, albeit significantly less efficient than the corresponding isolated Cu(II) sites on alumina.
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Robert, Emma G. L. y Jérôme Waser. "Silylium-Catalyzed Activation of Donor- Acceptor Strained Rings and Annulation with Indoles". CHIMIA 78, n.º 4 (24 de abril de 2024): 234–37. http://dx.doi.org/10.2533/chimia.2024.234.
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Leveraging the unique reactivity profile of donor-acceptor aminocyclopropanes and cyclobutanes allows the preparation of complex nitrogen-substituted molecules. While most reports focus on donor-acceptor strained rings with two geminal carbonyl groups as acceptors, mono carbonyl acceptor systems, despite their synthetic relevance, have been considerably less studied. Herein we describe catalytic annulation reactions ofaminocyclopropane and aminocyclobutane monoesters employing silylium catalysis to activate these less reactive donor-acceptor systems.
Tesis sobre el tema "Chimical reactivity"
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Oltean, Mircea. "Etude théorique de la réactivité chimique : des nano-objets au suivi de l'entropie par métadynamique". Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENV077.
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The most theoretical method used to study the chemical reactivity is the search for stationary points of potential energy surface. But the increasing size of systems studied increases system flexibility and simulation's including the dynamic aspect becomes necessary. In this manuscript, we study various chemical problems. We have modeled the molecular switches and rotors. We tested for these systems as well as the interaction cryptophane-small molecules, where weak interactions play an important role, the validity of the DFT-D. From a viewpoint of chemical reactivity, we studied a cycloaddition reaction catalyzed by a complex of Pt (II). Finally we determined the thermodynamic quantities and in particular the entropy of pericyclic reactions: an intramolecular reaction Dies-Alder and Claisen reaction. All of these phenomena have been studied by metadynamics and / or static calculations. The first study allowed us to assess the interactions that are present in a molecular switch and a rotor. Based on these interactions we have proposed new substituent and the link between the substituent and the observed properties. Then we implemented the Grimme approach to take account of London dispersion interactions for Pt atom in the software Gaussian09. The last part of the manuscript proposed two implementations: one for monitoring the entropic effect by using the energy as a collective variable in the metadynamics simulations, the other on the method of bias- exchange metadynamicsLa méthode théorique la plus utilisée pour étudier la réactivité chimique est la recherche des points stationnaires de la surface d'énergie potentielle. Mais la taille croissante des systèmes étudiés augmente la flexibilité du système et des simulations incluant l'aspect dynamique devient alors nécessaire. Dans le présent manuscrit, nous étudions diverses problématiques chimiques. Nous avons ainsi modélisé des interrupteurs et rotors moléculaires. Nous avons testé pour ces systèmes ainsi que pour l'interaction cryptophane-petites molécules, où les interactions faibles jouent un rôle important, la validité des DFT-D. D'un point de vue de la réactivité chimique, nous avons étudié une réaction de cycloaddition catalysée par un complexe de Pt (II). Finalement nous avons déterminé les grandeurs thermodynamiques et en particulier l'entropie de réactions péricycliques : une réaction intramoléculaire Dies-Alders et la réaction de Claisen. L'ensemble de ces phénomènes a été étudié par métadynamique et/ou calculs statiques. La première étude nous a permis d'évaluer les interactions, qui sont présentes dans un interrupteur et un rotor moléculaire. Sur la base de ces interactions nous avons proposé des nouveaux substituant et fait le lien entre la nature du substituant et les propriétés observées. Puis, nous avons implémenté l'approche de Grimme pour tenir compte des interactions de type London dans le logiciel Gaussian09 pour l'atome de Pt. La dernière partie du manuscrit propose deux implémentations : l'une pour le suivi des effets entropiques en utilisant l'énergie comme variable collective dans la métadynamique, l'autre concernant la méthode du bias-exchange-métadynamique
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Fazzini, Silvia <1983>. "Silica-Supported Gold Nanoparticles: Synthesis, Characterization and Reactivity". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6499/15/Fazzini_Silvia_tesi.pdf.
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The main aim of this work was the synthesis and applications of functionalized-silica-supported gold nanoparticles. The silica-anchored functionalities employed, e.g. amine, alkynyl carbamate and sulfide moieties, possess a notable affinity with gold, so that they could be able to capture the gold precursor, to spontaneously reduce it (possibly at room temperature), and to stabilize the resulting gold nanoparticles. These new materials, potentially suitable for heterogeneous catalysis applications, could represent a breakthrough among the “green” synthesis of supported gold nanoparticles, since they would circumvent the addition of extra reducing agent and stabilizers, also allowing concomitant absorption of the active catalyst particles on the support immediately after spontaneous formation of gold nanoparticles. In chapter 4 of this thesis is also presented the work developed during a seven-months Marco Polo fellowship stay at the University of Lille (France), regarding nanoparticles nucleation and growth inside a microfluidic system and the study of the corresponding mechanism by in situ XANES spectroscopy. Finally, studies regarding the reparation and reactivity of gold decorated nanodiamonds are also described.
Various methods of characterization have been used, such as ultraviolet-visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), X-ray Fluorescence (XRF), Field Emission Gun Scanning Electron Microscopy (SEM-FEG), X-ray Photoionization (XPS), X ray Absorption Spectroscopy (XAS).
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Fazzini, Silvia <1983>. "Silica-Supported Gold Nanoparticles: Synthesis, Characterization and Reactivity". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6499/.
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The main aim of this work was the synthesis and applications of functionalized-silica-supported gold nanoparticles. The silica-anchored functionalities employed, e.g. amine, alkynyl carbamate and sulfide moieties, possess a notable affinity with gold, so that they could be able to capture the gold precursor, to spontaneously reduce it (possibly at room temperature), and to stabilize the resulting gold nanoparticles. These new materials, potentially suitable for heterogeneous catalysis applications, could represent a breakthrough among the “green” synthesis of supported gold nanoparticles, since they would circumvent the addition of extra reducing agent and stabilizers, also allowing concomitant absorption of the active catalyst particles on the support immediately after spontaneous formation of gold nanoparticles. In chapter 4 of this thesis is also presented the work developed during a seven-months Marco Polo fellowship stay at the University of Lille (France), regarding nanoparticles nucleation and growth inside a microfluidic system and the study of the corresponding mechanism by in situ XANES spectroscopy. Finally, studies regarding the reparation and reactivity of gold decorated nanodiamonds are also described.
Various methods of characterization have been used, such as ultraviolet-visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), X-ray Fluorescence (XRF), Field Emission Gun Scanning Electron Microscopy (SEM-FEG), X-ray Photoionization (XPS), X ray Absorption Spectroscopy (XAS).
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Corti, Vasco <1991>. "Breaking reactivity borders: engineering stereoselective reactions with organocatalytic tools". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8996/1/PhD_dissertation_Vasco_Corti.pdf.
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The research focuses of my graduate education have been dealing with two main topics: the development of stereodivergent organocatalytic processes and the development of asymmetric dual-catalytic transformations. With regard to the first topic, stereodivergent processes can be defined as the synthetic sequence that allows accessing any given stereoisomers of the same product, which bears multiple stereocentres, from the same set of starting materials. The applied strategies led to the development of the first organocatalytic asymmetric example of sulfa-Michael-reductive amination synthetic sequence to access optically active 1,5-benzothiazepines, which are attractive scaffolds in the pharmaceutical field. In addition to this, thanks to a sequential catalytic approach, we developed the stereodivergent synthesis of β,β-disubstituted-α-amino acid derivatives. This protocol gives access to all the stereoisomeric forms of the desired product bearing two contiguous chiral centres. With respect to the second topic, multicatalysis strategies have emerged as powerful tool in reaction engineering. In particular, synergistic catalysis wherein two catalysts/catalytic cycles work in concert to create new bonds has attracted a great attention. With this focus in mind, we recently started to study the catalytic asymmetric [3+2] formal cycloaddition of vinylcyclopropanes and imines promoted by a palladium based metal catalyst and a chiral phosphoric acid as organocatalysts obtaining promising results in terms of reactivity and stereoselectivity. Furthermore, during my visiting period at Aarhus university, under the supervision of Prof. Karl Anker Jørgensen, I had the chance to develop the dual catalytic asymmetric oxidative γ-coupling of α,β-unsaturated aldehydes with air as the terminal oxidant obtaining the desired enantioenriched product with excellent stereoinduction and good yield values.
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Ragone, Francesco. "A molecular dymanics view of structure and reactivity". Doctoral thesis, Universita degli studi di Salerno, 2011. http://hdl.handle.net/10556/211.
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2009 - 2010The eld of computer simulations has developed into a very important branch of science providing a guess at the interactions between molecules to obtain predictions of properties as accurate as required, subject to the limitations imposed by the computer power and of the chosen and feasible theory level. Quantum chemical methods are predominantly applied to isolated molecules, which corresponds to the state of an ideal gas. Most chemical processes, however, take place in condensed phase, and the interaction of a molecule with its environment: the dimension and the huge amount of degrees of freedom of the system preclude the possiblity of quantum-level calculations. In this PhD thesis di erent approaches to treat several aspects of structure and reactivity, through the use of molecular dynamics techniques have been used. In the rst part, behaviour of Ru complexes relevant as (pre)catalysts for ole n metathesis have been inves- tigated. In particular, it has shed light on a so far underestimated key feature, i.e. the exibility around the N substituent: this allows NHCs to modulate their encumbrance in the rst coordination sphere of the metal to allow the coordination even for incoming bulky substrates. Furthermore, the reduced electron density on the MO of the methylidene group, due to the presence of a acid ligand trans have been analyzed, showing that it allows for a favorable interaction with the aromatic system of the proximal mesityl group of the NHC ligand, which leads to metallacycle rst and subsequently in the formation of a tensioned cyclopropane structure that nally evolves to the experimental product via a Buchner type ring expansion. Since the presence of a transition metal and the bonds breaking/formation the quantum approach is mandatory. On the other hand, the structure description of a Metal/polymer interface have been treated with classical coarse grained molecular dynamics approach. The calculated radial density pro les allowed to get atomistic insights in the Metal/polymer interface. In both cases of non coated and coated gold nanoparticles the polystyrene chains expose the phenyl rings to the nanoparticle surface. In the case of coated nanoparticles there is some penetration of the polystyrene phenyl rings into nanoparticle coating layer. When it is present, the third organic component (8 hydroxyquinoline) is closer to the nanoparticle surface and when in contact with a coated nanoparticle shows a deeper penetration into the thiols layer. The orientation of 8 hydroxyquinoline results short range and parallel with respect to the surface of non coated gold nanoparticles. Di erent is the 8 hydroxyquinoline orientation in the case of a coated gold nanoparticle. In this case the orientation results perpendicular to the nanoparticle surface.[edited by author]
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Tamboli, Vajir Fakirsab. "An Electrospray Ionization Mass Spectrometric Study on Reactivity of Resveratrol Induced by Metal Ions". Doctoral thesis, University of Trento, 2011. http://eprints-phd.biblio.unitn.it/658/1/FINAL_VERSION_OF_THESIS.pdf.
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Resveratrol is a polyphenolic compound produced by various plants and present in dietary sources such as red wine. In recent years, its beneficial effects for human health, including protection from heart diseases and cancer prevention, have attracted increasing interest. Resveratrol acts both as an antioxidant and a prooxidant agent when works in vivo with Cu(II) ions occurring naturally in living organisms. The aim of this work is to study the gas phase reactivity of resveratrol in presence of copper and iron ions, in order to more insights on the role of copper in the proposed biological mechanism. By electrospray ionization (ESI) mass spectrometry we have produced and detected some resveratrol-copper complexes by using a resveratrol/CuSO4 solution in acetonitrile/water, and their most stable structures have been calculated at the B3LYP/6-311G(d) level of theory. The formation of dehydrodimer product was also detected in ESI-MS/MS experiments and its structure assigned with evidences for isomeric compounds from copper and iron reactions with resveratrol. Density Functional Theory (DFT) calculations have been carried out to elucidate reaction mechanisms. Finally, the crucial role of the para-OH group in resveratrol structure has been demonstrated by investigating reactions with copper sulfate of synthetic analogues, bearing different number and position of OH groups.
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Ruggieri, Silvia <1991>. "Synthesis, Characterization and Reactivity of New Heterometallic Rhodium Carbonyl Nanoclusters". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8889/1/Ruggieri_Silvia_Tesi.pdf.
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The aim of my Ph.D. was to widen the chemistry of heterometallic Rh carbonyl clusters and synthesise and characterize new atomically-precise nanoclusters. Along with this, we evaluated the cytotoxicity of some heterometallic clusters through preliminary biological tests against different cell lines, in order to investigate their possible use in biology. Finally, we started testing homometallic Rh clusters in catalytic processes to compare their performances in low-temperature steam reforming reactions with more conventional Rh-based catalysts.
More specifically, over these years we focused our attention on the study of four systems, Rh-Bi, Rh-Ge, Rh-Sb and Rh-Au obtaining several new compounds, which we characterized through single crystal X-ray diffractometry, IR spectroscopy, ESI-MS spectrometry and, in some cases, 31P{1H} NMR.
As for the biological part, during my period at the Ecole Polytechnique Fédérale de Lausanne (EPFL), we tested some of our new Rh clusters against three cell lines, namely A2780, A2780cisR and HEK-293, in order to evaluate our species as potential cytotoxic agents. The Rh-Ge clusters achieved the best results.
Finally, in collaboration with another research group of our same Department, we tested some Rh clusters as active phases in catalysts for the methane steam reforming at low temperature, obtaining similar results with those achieved by using a conventional Rh-based catalyst.
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Calvaresi, Matteo <1979>. "Computational investigation of structure and reactivity in organic and bio-organic chemistry". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/1038/1/Tesi_Calvaresi_Matteo.pdf.
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Calvaresi, Matteo <1979>. "Computational investigation of structure and reactivity in organic and bio-organic chemistry". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/1038/.
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Basolo, L. "SYNTHESIS AND REACTIVITY OF N-CONTAINING HETEROCYCLES THROUGH CATALYTIC SYSTEMS". Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150083.
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N-containing heterocycles are the more represented in natural products and drugs. Our research has been focused on various aspects of heterocycles synthesis and reactivity. For this purpose we use transition metals catalysis, among which Pd has a central role due to the existence of different and easily and interconvertible oxidation states, Pd(0), Pd(II) and Pd(IV).
For the arylation reaction electron poor aryl derivatives are problematic substrates, but we are successful in apply an intramolecular Pd(0) catalyzed reaction, in ligand free conditions, to synthesize azine and diazine polyheterocycles.
Following our study on the reactivity and functionalization of indole derivatives we focus our attention on the amination reaction applied to the heterocycle indoline. The indoline skeleton is a ubiquitous scaffold found in many biologically active alkaloids and pharmaceutically active compounds, useful even as chiral auxiliary and for advanced materials. We selected the best conditions to functionalize this heterocycle at the nitrogen atom; then we find environmental friendly conditions using a solvent-free, microwaves assisted, reaction method and substantially reducing the catalyst load. Further to this we demonstrate the possibility of making Pd(0)-catalyzed amination reactions even in ligand-free conditions.
In the third part we study a new synthesis of tetracyclic 1,4-Benzodiazepin-5-ones. The exploited reactions are Pd(0) catalyzed heterocyclization on imidazolidinones allenylamide followed by 1,3-dipolar cycloaddition. In the last step of the synthesis we obtain an unexpected total diasteroselectivity so we make a DFT and HF computational study that justify our results also thanks to the use of the recent QTAIM theory.
In the last part we use Pd(II) and Au(III)-catalyzed reactions to realize C-H activation reaction. Starting from isoxazol-5-ones we obtain a solvent based regioselectivity in the alkenylation with acrylates or propiolates. The use of Pd(II)/O2 catalysis with acrylates lead to regioselectivity but with low yield; Au(III) catalysis with propiolates gives better yield and shows a complete regioselectivity.