Search results for "hydrogenation"

A combined NMR, DFT, and X-ray investigation of some cinchona alkaloid O-ethers.

2008

Structures and conformational behavior of several cinchona alkaloid O-ethers in the solid state (X-ray), in solution (NMR and DFT), and in the gas phase (DFT) were investigated. In the crystal, O-phenylcinchonidine adopts the Open(3) conformation similar to cinchonidine, whereas the O-methyl ether derivatives of both cinchonidine and cinchonine are packed in the Closed(1) conformation. Dynamic equilibria in solutions of the alkaloids were revealed by combined experimental-theoretical spin simulation/iteration techniques for the first time. In the (1)H NMR spectra in CDCl3 and toluene-d8 at room temperature, Closed(1) conformation was observed for the O-silyl ethers as a separate set of sign…

Enzymatic and pharmacokinetic studies on the metabolism of branched chain alpha-keto acids in the rat.

1983

Michaelis-constants and enzyme activities for dehydrogenation and transamination of the three branched chain alpha-keto acids in liver, kidney, skeletal muscle, and brain of rats are reported. After oral load only 11-22% of the keto acids pass the liver unchanged. Blood levels in pharmacokinetic and absorption studies are related to the Michaelis-constants. At the low keto-acid concentrations after oral application, dehydrogenation in the non-hepatic tissues is supposed to prevail over transamination. Data on feed efficiency of branched chain alpha-keto acids reported in the literature support this view. The chance for transamination is better after intravenous administration. The transfera…

Dietary Fatty Acids in Metabolic Syndrome, Diabetes and Cardiovascular Diseases

2011

In the last few decades, the prevalence of overweight and essential obesity has been undergoing a fast and progressive worldwide increase. Obesity has been in turn linked to type II diabetes, with the total number of diabetic patients worryingly increasing, in the last fifteen years, suggesting a pandemic phenomenon. At the same time, an increase in the prevalence of cardiovascular diseases has been also recorded. Increasing evidence suggests that the diet is involved in such escalation. In particular, the progressive globalization of food industry allowed massive supply, at a relatively low price, of a great variety of pre-packed food and bakery products, with very high energy content. Mos…

Metal‐ and Reagent‐Free Anodic Dehydrogenative Cross‐Coupling of Naphthylamines with Phenols

2018

Pd supported on magnetic carbon coated halloysite as hydrogenation catalyst: Study of the contribution of carbon layer and magnetization to the catal…

2019

Abstract In this article, a magnetic carbon-coated halloysite nanoclay (Hal) was prepared through introduction of hydrothermally carbonized glucose (Glu) on Hal followed by the immobilization of magnetic nanoparticles (MNPs) and incorporation of resorcinol-formaldehyde polymeric shell (RF) and carbonization. The resulting composite was then successfully applied for the immobilization of Pd nanoparticles to afford Pd@Hal@Glu-Fe-C that could efficiently promote hydrogenation of nitroarenes in the aqueous media at low temperature. The catalyst exhibited high selectivity toward nitro group. Moreover, it was highly recyclable with low MNPs and Pd leaching. To elucidate the contribution of each c…

Oxidative dehydrogenation of ethane on Te-containing MoVNbO catalysts

2004

Abstract Ethylene has selectively been obtained during the oxidative dehydrogenation of ethane on a Mo–V–Te–Nb–O mixed oxide catalyst. The catalyst was prepared hydrothermally and heat-treated at 600 °C for 2 h in a N2-stream. For comparison, undoped and Te-doped Mo–V–Nb–O catalysts and Mo–V–Te–O and Mo–Te–Nb–O mixed oxides have also been prepared. The catalytic performance of the Mo–V–Nb–Te–O mixed oxide catalyst cannot be explained by the incorporation of Te on the surface of a Mo–V–Nb–O mixed oxide but by the presence of an orthorhombic Te2M20O57 (M=Mo, V, Nb) crystalline phase. The role of tellurium in these catalysts is also discussed.

Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions

2020

The vast potential of organic materials for electronic, optoelectronic and spintronic devices entails substantial interest in the fabrication of π-conjugated systems with tailored functionality directly at insulating interfaces. On-surface fabrication of such materials on non-metal surfaces remains to be demonstrated with high yield and selectivity. Here we present the synthesis of polyaromatic chains on metallic substrates, insulating layers, and in the solid state. Scanning probe microscopy shows the formation of azaullazine repeating units on Au(111), Ag(111), and h-BN/Cu(111), stemming from intermolecular homo-coupling via cycloaddition reactions of CN-substituted polycyclic aromatic az…

Atomically Precise, Thiolated Copper–Hydride Nanoclusters as Single-Site Hydrogenation Catalysts for Ketones in Mild Conditions

2019

Copper-hydrides are known catalysts for several technologically important reactions such as hydrogenation of CO, hydroamination of alkenes and alkynes, and chemoselective hydrogenation of unsaturated ketones to unsaturated alcohols. Stabilizing copper-based particles by ligand chemistry to nanometer scale is an appealing route to make active catalysts with optimized material economy; however, it has been long believed that the ligand-metal interface, particularly if sulfur-containing thiols are used as stabilizing agent, may poison the catalyst. We report here a discovery of an ambient-stable thiolate-protected copper-hydride nanocluster [Cu25H10(SPhCl2)18]3- that readily catalyzes hydrogen…

The Hydrogen‐Storage Challenge: Nanoparticles for Metal‐Catalyzed Ammonia Borane Dehydrogenation

2021

International audience; Dihydrogen is one of the sustainable energy vectors envisioned for the future. However, the rapidly reversible and secure storage of large quantities of hydrogen is still a technological and scientific challenge. In this context, this review proposes a recent state-of-the-art on H 2 production capacities from the dehydrogenation reaction of ammonia borane (and selected related amine-boranes) as a safer solid-source of H 2 by hydrolysis (or solvolysis), according to the different developed nanoparticle-based catalysts. The review groups the results according to the transition metals constituting the catalyst according a special view to current cost/availability consid…

Mixed oxide Ti Si O prepared by non-hydrolytic Xerogel method as a diluter of nickel oxide for the oxidative dehydrogenation of ethane

2018

Abstract Mixed Ti Si O materials prepared by non-hydrolytic xerogel method have been employed as diluters for nickel oxide and used in the catalytic oxidative dehydrogenation of ethane. These catalysts have been characterized by several physicochemical techniques such as N2 adsorption, XRD, TPR, TEM, HR-TEM, and XPS. Supported nickel oxide catalysts have been reported to be efficient but only if the nature and the amount of support are controlled. In the present article it is shown that highly loaded (80 wt% NiO) nickel catalysts are more efficient when diluted on mixed Ti Si O materials with appropriate Ti/Si ratios than on pure TiO2 and SiO2 diluters. The catalytic results have been expla…