Search results for "olefin"
showing 10 items of 147 documents
Effect of AlR3 (R = Me, Et, iBu) addition on the composition and microstructure of ethylene/1-olefin copolymers made with post-metallocene complexes …
2018
The effect of trialkylaluminum compound (AlR3, where R = Me, Et, iBu) addition on the performance of the [LigZrCl]2(μ-O)/AliBu3/Ph3CB(C6F5)4 and LigTiCl2/AliBu3/Ph3CB(C6F5)4 (Lig = Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)2) catalysts in ethylene/1-olefin copolymerization was investigated. The presence of AlMe3 in the feed during the copolymerization process catalyzed by the diamine-bis(phenolate) zirconium catalyst greatly increases the amount of incorporated comonomer and leads to microstructural changes, e.g., the formation of blocky and alternating sequences of 1-olefin units. Moreover, the use of AlMe3 limits the reaction yield and decreases the molecular weight of the produced copolymers. Th…
Mejora en la detección y el tratamiento de datos en técnicas de separación a alta temperatura para la caracterización de poliolefinas
2014
La Tesis Doctoral es una contribución al reconocimiento de la importancia de la caracterización de la interdependencia entre la masa molecular y la composición química en poliolefinas, y del potencial de los detectores de absorción infrarroja (IR) de filtros en este campo. El uso de este tipo de detectores acoplados a la técnica de separación por masas moleculares GPC/SEC (Gel permeation chromatography/Size exclusion chromatography) se ha ido popularizando en los últimos años, al ponerse en valor el tipo de información que proporcionan, y se prevé que la tendencia se acentúe en el futuro, con la extensión de su aplicación como detectores duales de concentración y de composición química en o…
Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation
2015
An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with…
The fluxional behaviour of η6(bicyclo[6.2.0]deca-2,4,6-triene) hexacarbonyl diruthenium (Ru-Ru) by 1H and 13C NMR techniques
1977
Abstract The variable temperature 1 H NMR spectra of [Ru 2 (CO) 6 η 6 -C 10 H 12 )] (C 10 H 12 = bicyclo [6.2.0]-deca-2,4,6-triene) shows that this molecule undergoes the fluxional behaviour previously reported for [M 2 (CO) 6 (η 6 -polyolefin)] complexes (M = Fe, Ru) which have in the solid an asymmetric skew-type structure. The use of 13 C NMR techniques, employed for the first time for a diruthenium complex of the above type, allows a comparison of the mechanism of the fluxional process with that of the diiron analog. Although the observed line shape changes of the carbonyl resonances in the two complexes are somewhat different the process are basically the same. In the case of the dirut…
Diversity-Oriented Synthesis of Highly Functionalized Alicycles across Dipolar Cycloaddition/Metathesis Reaction
2021
AbstractThis Account gives an insight into the selective functionalization of some readily available commercial cyclodienes across simple chemical transformations into functionalized small-molecular scaffolds. The syntheses involved selective cycloadditions, followed by ring-opening metathesis (ROM) of the resulting azetidin-2-one derivatives or isoxazoline frameworks and selective cross metathesis (CM) by discrimination of the C=C bonds on the alkenylated heterocycles. The CM protocols have been described when investigated under various conditions with the purpose on exploring chemodifferentiation of the olefin bonds and a study on the access of the corresponding functionalized β-lactam or…
ChemInform Abstract: First Synthesis of Medium-Sized Ring Allenyl Lactams.
2012
Medium-sized lactams bearing an axially chiral allene unit have been synthesized by using an aza-ketene Claisen rearrangement. Starting from 2-alkynylpiperidines or 2-alkynylazepines, ring enlargement enabled the highly diastereoselective formation of 10- or 11-membered lactams with a 4,5-allene subunit. X-ray analysis of the allenylacezinone showed the presence of a strained cumulated olefin system with a defined arrangement of the functional groups. The cyclic allenes were found to be stable upon heating up to 50 °C.
First Synthesis of Medium-Sized Ring Allenyl Lactams
2011
Medium-sized lactams bearing an axially chiral allene unit have been synthesized by using an aza-ketene Claisen rearrangement. Starting from 2-alkynylpiperidines or 2-alkynylazepines, ring enlargement enabled the highly diastereoselective formation of 10- or 11-membered lactams with a 4,5-allene subunit. X-ray analysis of the allenylacezinone showed the presence of a strained cumulated olefin system with a defined arrangement of the functional groups. The cyclic allenes were found to be stable upon heating up to 50 °C.
A Straightforward Electroactive π-Extended Tetrathiafulvalene (exTTF) Building Block
2012
The synthesis and X-ray structure of a new and readily available exTTF derivative (6) bearing a methyltriphenylphosphonium bromide moiety as a new building block for the construction of electroactive molecules is reported. The phosphonium salt 6, which was prepared in one step from 2-hydroxymethyl-exTTF as a stable yellow solid in 84 % yield, efficiently undergoes Wittig olefination reactions with a variety of aldehydes to predominantly form the E isomer. Electronic spectra and cyclic voltammetry of the novel compounds reveal the electronic communication between the electroactive units.
Janus Micelles Induced by Olefin Metathesis
2008
A facile one-step procedure for hydrophobic modification and simultaneous TEM contrast enhancement via a regioselective olefin metathesis reaction using Grubbs' catalyst is presented. Polyether diblock copolymers were investigated, and both the chain ends of the hydrophilic and the hydrophobic block were hydrophobically modified. Modification of the hydrophilic block results in nonsymmetric supramolecular structures (Janus micelles) which self-assemble into larger hierarchically organized super-micelles.