Reversed impregnation

The hydration of triple bonds is generally carried out with mercuric ion salts (often the sulfate or acetate) as catalysts. Mercuric oxide in the presence of an acid is also a common reagent. Since the addition follows Markovnikov s rule, only acetylene gives an aldehyde. All other triple-bond compounds give ketones (for a method of reversing the orientation for terminal alkynes, see 15-16). With allqmes of the form RC=CH methyl ketones are formed almost exclusively, but with RC=CR both possible products are usually obtained. The reaction can be conveniently carried out with a catalyst prepared by impregnating mercuric oxide onto Nafion-H (a superacidic perfluorinated resinsulfonic acid). ... 

A series of CoSx-MoSx/NaY catalysts was synthesized by intoducing Co(CO)3NO into MoSx/NaY evacuated at 673 K for 1 h, followed by second programmed sulfidation procedures. MoSx-CoSx/NaY catalysts were prepared in the reversed order of the metal sulfide accommodations into the zeolite cavities. When Co2(CO)g was used as the Co precursor, MoSx/NaY was impregnated with COj(CO)g dispersed in n-hexane, followed by evacuation at room temperature to remove the solvent. Co2(CO)g/MoSx/NaY was subsequently sulfided at 673 K to give CoSx/MoSx/NaY. The catalyst composition was determined by AAS and ICP. 

Figure 2 schematically presents a synthetic strategy for the preparation of the structured catalyst with ME-derived palladium nanoparticles. After the particles formation in a reverse ME [23], the hydrocarbon is evaporated and methanol is added to dissolve a surfactant and flocculate nanoparticles, which are subsequently isolated by centrifugation. Flocculated nanoparticles are redispersed in water by ultrasound giving macroscopically homogeneous solution. This can be used for the incipient wetness impregnation of the support. By varying a water-to-surfactant ratio in the initial ME, catalysts with size-controlled monodispersed nanoparticles may be obtained. 

A simple and rapid method of separating optical isomers of amino acids on a reversed-phase plate, without using impregnated plates or a chiral mobile phase, was described by Nagata et al. [27]. Amino acids were derivatized with /-fluoro-2,4-dinitrophenyl-5-L-alanine amide (FDAA or Marfey s reagent). Each FDAA amino acid can be separated from the others by two-dimensional elution. Separation of L- and D-serine was achieved with 30% of acetonitrile solvent. The enantiomers of threonine, proline, and alanine were separated with 35% of acetonitrile solvent and those of methionine, valine, phenylalanine, and leucine with 40% of acetonitrile solvent. The spots were scraped off the plate after the... 

The most widely used approach for the separation of enantiomers by TLC is based on a ligand exchange mechanism using commercially available reversed-phase plates impregnated with a solution of copper acetate and (2S,4R,2 RS)-4-hydroxy-l-(2-hydroxydodecyl)proline in optimized amounts. Figure 7.9 (10,97,98,107-109). Enantiomers are separated based on the differences in the stability of the diastereomeric complexes formed between the sample, copper, and the proline selector. As a consequence, a prime requirement for separation is that the seumple must be able to form complexes with copper. Such compounds include... 

Tap water Extract compound with solid-phase extraction technique that uses a membrane impregnated with reverse-phase particles elute with acetonitrile LC Low ppb (pg/L) 82-93 Hagen et al. 1990... 

Bimetallic particles with a very narrow size distribution of circa 1.5 nm have been prepared by decarbonylation under H2 at 400 °C of the impregnated Ru5PtC(CO)i6 on carbon black. EXAFS data indicate that a surface segregation of Pt on the fee Ru structure occurs in the bimetallic nanoparticles. Moreover, they undergo reversible oxidation, forming a MO surface and a core of metal [62]. 

Direct chromatographic determination of octanol-water partition coefficients has been attempted using a Corasil I column impregnated with octanol (287) or a reversed-phase column which had been coated with octanol (288). In either case, the sample was injected into an aqueous mobile phase. When the octanol-coated octyidecyl silica support was used, the... 

Surface engineering of polymers by infusion. Supercritical-fluid contact can reversibly swell some polymer surfaces and films thus helping to enhance impregnation by monomers with subsequent polymerization to form nanocomposite anchored layers. - ... 

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