Browsing by Subject "Hydrocarbons"

Now showing 1 - 7 of 7
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    Accurate ring strain energy calculations on saturated three-membered heterocycles with one group 13–16 element
    (American Chemical Society, 2020-08-17) Rey Planells, Alicia; Espinosa Ferao, Arturo; Química Orgánica
    Accurate ring strain energy (RSE) data for parent (CH2)2X rings are reported, where X are group 13–16 elements (El) in their lowest oxidation state, from the second to the sixth row, with their covalence completed by bonds to H. They are obtained from appropriate homodesmotic and hyper-homodesmotic reactions at different levels up to the CCSD(T) level, thus providing a benchmark of high-quality reference RSE values, as well as acceptably accurate faster lower-level options. Derivatives of indium, thallium, and lead cannot be properly described by a three-member ring connectivity, because they display a unique donor–acceptor structure from an ethylene π(C═C) orbital to an empty p orbital of a metallylene subunit. The RSE of groups 13 and 14 heterocycles increases on descending in the group (except for Ga and Ge), while it decreases for groups 15 and 16. The latter is presumably due to a strain-releasing mechanism favored by the increase of p-character at the sp3-type atomic orbital used by El in the endocyclic El–C bonds, %p(El)El-C, originated by the tendency of the El lone pairs in groups 15–16 to increase their s-character. This strain-releasing mechanism does not exist in heavier tetrels, which keep almost unchanged the p-character in the endocyclic bonds at El, whereas for triels the p-character is still lower owing to their sp2-like hybridization. Remarkable linear correlations were found between the RSE and either the above-mentioned %p(El)El-C, the distal C–C bond distance or the relaxed force constants for the endocyclic bond angles.
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    Ámbito de aplicación de la exención de avituallamientos de productos energéticos utilizados como combustible o carburante en la navegación y procesos de digitalización aplicables.
    (Colex, 2025) Sanz Castaño, José Francisco; Universidad de Murcia. Grupo de investigación: Fiscalidad: Tecnología, Empresa y Sociedad.
    En el presente artículo, con posterioridad a un acercamiento al ámbito de aplicación de la exención sobre el impuesto especial de fabricación en el avituallamiento de embarcaciones o aeronaves que realicen navegaciones distintas a las de recreo del artículo 51.2.a) y b) de la ley 38/1992, de 28 de diciembre, de impuestos especiales. Realizaremos un análisis de los procedimientos digitales y electrónicos asociados al transporte y circulación de los hidrocarburos. Concretamente, del procedimiento de circulación al amparo de un documento administrativo electrónico previsto en el artículo 29.B.2 del Reglamento de los Impuestos Especiales, y el procedimiento de ventas en ruta regulado en el artículo 27 del mismo reglamento.
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    Kinetics and mechanistic insights into the acetate-assisted dimerization of terminal alkynes under ruthenium- and acid-promoted (RAP) catalysis
    (American Chemical Society, 2017-09-21) Salvio, Riccardo; Juliá Hernández, Francisco; Pisciottani, Luca; Mendoza-Meroño, Rafael; García-Granda, Santiago; Bassetti, Mauro; Química Inorgánica
    The mechanism of the dimerization of terminal aryl alkynes promoted by [{RuCl(μ-Cl)(η6-p-cymene)}2](1)/AcOH, under cooperative transition metal/Brønsted acid catalysis, has been investigated with regard to (i) the activation of the dinuclear ruthenium complex and (ii) the catalytic formation of the trans-1,4-diaryl-1,3-enyne products, by a detailed kinetic investigation of both processes. Complex 1 is subject to a slow solvolytic process in neat acetic acid or is transformed rapidly in the presence of sodium acetate to form the monomeric ruthenium(II) acetato complex [RuCl(η6-pcymene)(OAc)]. The latter is the active catalytic species promoting the alkyne dimerization process, via initial π-alkyne coordination and intramolecular C−H abstraction by the acetate ligand, as key steps of the catalytic cycle. The presence of additive acetate salts allows for the reaction to proceed at room temperature with short reaction times and high trans/cis stereoselectivity, thus rendering this catalytic system among the most active and selective procedures for the dimerization of terminal alkynes in a protic medium. The linear coupling of three molecules of phenylacetylene affords an organometallic ruthenium complex featuring a butenynyl ligand which has been characterized by X-ray crystallography.
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    Nudo territorial y desterritorialización indígena en Loma Campana (Neuquén, Argentina) desde 1963.
    (Asociación Española de Americanistas, 2021) Aguirre, Sabrina
    El escrito analiza cómo las políticas estatales provinciales configuraron nudos territoriales en la zona donde se ubica la comunidad Campo Maripe, al norte de Añelo, el corazón de la formación geológica Vaca Muerta. Se sostiene que estas políticas diseñaron los espacios impulsando territorialidades asociadas a determinadas actividades económicas y trajeron como consecuencia la desterritorialización indígena. La comunidad Campo Maripe, cuyo territorio actualmente se superpone parcialmente con el yacimiento hidrocarburífero Loma Campana -uno de los tres más relevantes en la extracción por métodos no convencionales-, ha sido seleccionada como caso de estudio en función de la notoriedad de sus estrategias de resistencia durante los últimos años. Se utilizan fuentes escritas y orales para caracterizar el complejo panorama de la superposición de territorialidades a partir de las políticas provinciales y el desarrollo de dinámicas específicas en las interacciones de los diferentes actores dentro de los nudos territoriales.
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    Ru-catalyzed C–H arylation of fluoroarenes with aryl halides
    (American Chemical Society, 2016-03-04) Simonetti, Marco; Perry, Gregory J. P.; Cambeiro, Xacobe C.; Juliá Hernández, Francisco; Arokianathar, Jude N.; Larrosa, Igor; Química Inorgánica
    Although the ruthenium-catalyzed C−H arylation of arenes bearing directing groups with haloarenes is wellknown, this process has never been achieved in the absence of directing groups. We report the first example of such a process and show that unexpectedly the reaction only takes place in the presence of catalytic amounts of a benzoic acid. Furthermore, contrary to other transition metals, the arylation site selectivity is governed by both electronic and steric factors. Stoichiometric and NMR mechanistic studies support a catalytic cycle that involves a well-defined η6-arene-ligandfree Ru(II) catalyst. Indeed, upon initial pivalate-assisted C−H activation, the aryl-Ru(II) intermediate generated is able to react with an aryl bromide coupling partner only in the presence of a benzoate additive. In contrast, directing-group-containing substrates (such as 2-phenylpyridine) do not require a benzoate additive. Deuterium labeling and kinetic isotope effect experiments indicate that C−H activation is both reversible and kinetically significant. Computational studies support a concerted metalation−deprotonation (CMD)-type ruthenation mode and shed light on the unusual arylation regioselectivity.
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    Site-selective catalytic carboxylation of unsaturated hydrocarbons with CO2 and water
    (American Chemical Society, 2017-08-16) Gaydou, Morgane; Moragas, Toni; Juliá Hernández, Francisco; Martin, Ruben; Química Inorgánica
    A catalytic protocol that reliably predicts and controls the site-selective incorporation of CO2 to a wide range of unsaturated hydrocarbons utilizing water as formal hydride source is described. This platform unlocks an opportunity to catalytically repurpose three abundant, orthogonal feedstocks under mild conditions.
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    Walking metals for remote functionalization
    (American Chemical Society, 2018-02-08) Sommer, Heiko; Juliá Hernández, Francisco; Martin, Ruben; Marek, Ilan; Química Inorgánica
    The distant and selective activation of unreactive C−H and C−C bonds remains one of the biggest challenges in organic chemistry. In recent years, the development of remote functionalization has received growing interest as it allows for the activation of rather challenging C−H and C−C bonds distant from the initiation point by means of a “metal-walk”. A “metal-walk” or “chain-walk” is defined by an iterative series of consecutive 1,2- or 1,3-hydride shifts of a metal complex along a single hydrocarbon chain. With this approach, simple building blocks or mixtures thereof can be transformed into complex scaffolds in a convergent and unified strategy. A variety of catalytic systems have been developed and refined over the past decade ranging from late-transition-metal complexes to more sustainable iron- and cobalt-based systems. As the possibilities of this field are slowly unfolding, this area of research will contribute considerably to provide solutions to yet unmet synthetic challenges.