189,028 research outputs found
Cleaner Routes for Friedel-Crafts Acylation
No full textFriedel-Crafts acylation is among the most fundamental and useful reactions to yield aromatic ketones but it is one of the less acceptable in terms of unwanted polluting by-products or atom economy because of the overconsumption of catalyst which is used in stoichiometric quantities in the conventional process. This route is nevertheless widely used in the fine chemical industry.In recent years, awareness of the impact of industrial activities on the environment has led chemists to work on new chemical routes, less dangerous and more environmentally friendly.We considered here the acylation of a benzofurane derivative by an acyl chloride, as an intermediary step for a pharmaceutical product. In this study, one of the first alternatives was to replace conventional catalysts (FeCl3 or AlCl3), by reusable solid catalysts. Indeed, a wide variety of new solid catalysts, more efficient and less polluting, has now emerged (zeolites, ion-exchange resins…). In this work, these catalysts were first tested in “conventional” conditions, i.e., using an organic solvent (1,2-dichlorobenzene in our case), to determine the best one, in terms of reactivity, lifetime and reusability. The zeolite Y was found the most appropriate.However, the use of an organic solvent still remains questionable and the use of supercritical carbon dioxide as the solvent was also considered. Its inherent properties include non-flammability, mild critical conditions, tuneable solubility near to the critical point and very low environmental impact. The reaction was operated using a continuous high pressure fixed bed. Results concerning yield and selectivity are presented
La « crise » des U. P. hors de France
No full textFriedel Victor-Henri. La « crise » des U. P. hors de France. In: Revue internationale de l'enseignement, tome 46, Juillet-Décembre 1903. pp. 532-534
Géochimie et hydrogéologie des enveloppes aqueuses et des eaux thermales par P. Urbain,1967
No full textFriedel Jacques. Géochimie et hydrogéologie des enveloppes aqueuses et des eaux thermales par P. Urbain,1967. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 91, 1, 1968. p. 108
Friedel-Craft and Atom Transfer Radical Polymerization for Membrane and Inorganic Nanoparticles
No full textThis dissertation explores various facets of polymer science, including methods for synthesis, control of polymer sequencing, organic-inorganic nanoparticle synthesis, and the application of polymer membranes. Chapter 1 provides an overview of polymer development, encompassing both chain growth and step growth polymerization methods, along with recent developments and advancements in the field. Additionally, it briefly outlines techniques for synthesizing organic-inorganic nanoparticles and its corresponding applications. In Chapter 2, attention is focused on the synthesis of polymeric membranes for alkaline exchange applications. A detailed examination of the structure-properties relationship is conducted by introducing membranes with varying percentages of charged groups. Furthermore, block copolymers are synthesized to enhance conductivity by facilitating the formation of ion channels. Comprehensive characterization techniques, including measurements of molecular weight, morphology, conductivity, and stability, are employed to validate the membranes' performance. Chapter 3 describes an intriguing discovery of through-space conjugation, exhibited by monomers and oligomers that were produced by acid-catalyzed Friedel-Craft hydroxylation of 1,4-disubstituted benzene and benzaldehyde derivatives. The compounds emit blue light under 300 nm UV irradiation, and the mechanism was explored through structural variation and experimental data analysis. Chapter 4 employs the spytag spycatcher method to modify polymer layers on a nanoparticle, enabling attachment of diverse functional proteins for tailored applications. Additionally, the chapter discusses the recycling of rare earth elements through the coating of magnetic nanoparticles with the protein LanM, facilitating the selective adsorption of these elements from waste streams, followed by their easy recovery under acidic conditions.</p
Sur un gisement de stannine en France
No full textFriedel Georges. Sur un gisement de stannine en France. In: Bulletin de la Société française de Minéralogie, volume 35, 5, 1912. p. 236
Sur la croissance et la décroissance des cristaux (note rectificative)
No full textFriedel Georges. Sur la croissance et la décroissance des cristaux (note rectificative). In: Bulletin de la Société française de Minéralogie, volume 50, 7-8, 1927. p. 464
Italie
No full textFriedel V.-H. Italie. In: La revue pédagogique, tome 51, Juillet-Décembre 1907. p. 289
Italie
No full textFriedel V.-H. Italie. In: La revue pédagogique, tome 51, Juillet-Décembre 1907. p. 289
Italie
No full textFriedel V.-H. Italie. In: La revue pédagogique, tome 51, Juillet-Décembre 1907. p. 386
Hydroarylation of Alkenes by protonation/Friedel-Crafts Trapping – HFIP-Mediated Access to Per-Aryl Quaternary Stereocentres
No full text
Upon treatment with a combination of HFIP
and a strong Brønsted acid, alkenes behave as Brønsted bases and protonate to give
carbocations which can be trapped by electron rich arenes. The reaction constitutes
a Friedel-Crafts (FC) hydroarylation which proceeds with Markovnikov
selectivity and is orthogonal to traditional metal catalyzed processes. The
products contain polyarylated quaternary carbon atoms which are difficult to
obtain via alternative methods. Intermolecular
transfer hydrogenation and
hydrothiolation are also demonstrated.
</div
- …
