A-vinyl pyrrolidone

Pt/Pd bimetallic nanoparticles can be prepared by refluxing the alcohol/water (1 1, v/v) solution of palla-dium(II) chloride and hexachloroplatinic(IV) acid in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) at ca. 95 °C for Ih [15,16,48]. The resulting Pd/Pt nanoparticles have a Pt-core/Pd-shell structure with a narrow size distribution and the dispersion is stable against aggregation for several years. The core/shell structure was confirmed by the technique of EAXFS. Composition of Pt/Pd nanoparticles can be controlled by the initially feed amount of two different metal ions, i.e., in this case one... 

In Figure 12a (Pd Pt = 1 2) and 12b (Pd Pt = 1 1), only the spectral feature of CO adsorbed on the Pt atoms, i.e., a strong band at 2068 cm and a very weak broad band at around 1880 cm was observed, while that derived from CO adsorbed on Pd atoms at 1941 cm is completely absent, which proved that the Pd-core has been completely covered by a Pt-shell. Recently we also characterized Au-core/Pd-shell bimetallic nanoparticles by the CO-IR [144]. Reduction of two different precious metal ions by refluxing in ethanol/ water in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, the bimetallic nanoparticles with a Au-core/Pd-shell structure are usually produced. In contrast, it is difficult to prepare bimetallic nanoparticles with the inverted core/shell, i.e., Pd-core/Au-shell structure. A sacrificial hydrogen strategy is useful to construct the inverted core/shell structure, where the colloidal dispersions of Pd cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly... 

In 1989, we developed colloidal dispersions of Pt-core/ Pd-shell bimetallic nanoparticles by simultaneous reduction of Pd and Pt ions in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) [15]. These bimetallic nanoparticles display much higher catalytic activity than the corresponding monometallic nanoparticles, especially at particular molecular ratios of both elements. In the series of the Pt/Pd bimetallic nanoparticles, the particle size was almost constant despite composition and all the bimetallic nanoparticles had a core/shell structure. In other words, all the Pd atoms were located on the surface of the nanoparticles. The high catalytic activity is achieved at the position of 80% Pd and 20% Pt. At this position, the Pd/Pt bimetallic nanoparticles have a complete core/shell structure. Thus, one atomic layer of the bimetallic nanoparticles is composed of only Pd atoms and the core is completely composed of Pt atoms. In this particular particle, all Pd atoms, located on the surface, can provide catalytic sites which are directly affected by Pt core in an electronic way. The catalytic activity can be normalized by the amount of substance, i.e., to the amount of metals (Pd + Pt). If it is normalized by the number of surface Pd atoms, then the catalytic activity is constant around 50-90% of Pd, as shown in Figure 13. 

A related Heck reaction of substituted o-bromoacetanilides with styrenes followed by selenium-induced cyclization of the resulting o-styiylacetanilides gives 2-arylindoles [378], Substituted o-bromonitrobenzenes react with ethyl vinyl ether under the influence of Pd(OAc)2 to give the corresponding o-ethoxyethenylnitrobenzenes. Zinc reduction then yields indoles [379]. The one-step Pd-catalyzed conversion of o-bromoanilines to indoles 302 with enamines (or with A/-vinyl-2-pyrrolidone) has been reported [380]. 

Crospovidone is a cross-linked homopolymer of A-vinyl-2-pyrrolidone. Acetylene and formaldehyde react to form butynediol. Hydrogenation and subsequent cyclodehydrogenation gives butyrolactone. The reaction of butyrolactone with ammonia produces pyrrolidone, which is vinylated with acetylene under pressure. The linear polymerization of the vinylpyrrolidone yields polyvinylpyrrolidone, a soluble binder, whereas the popcorn (branched) polymerization yields crospovidone, an insoluble... 

A-Vinyl-2-pyrrolidone (1.8 mol), 2,2 -azobis(2-methyl-N-(2-hydroxyethyl)-propio-namide) (0.018 mol), and 2-mercaptoethanol (0.072 mol) were dissolved in 3000 ml of 2-propanol degassed for 1 hour. The free radical polymerization was carried out at reflux while stirring for 44 hours. The mixture was concentrated and then dissolved in 400 ml of 4-methyl-2-pentanone and slowly precipitated into 5000 ml of t-butyl methyl ether. The suspension was filtered and the filter cake washed twice with 200 ml of -butyl methyl ether. The solid was purified by dissolving in 400 ml of... 

Preparation of poly(A-vinyl-2-pyrrolidone)-b-poly(D,L-lactide)... 

Information available in 1995 indicated that A-vinyl-2-pyrrolidone was produced in four countries (China, Germany, United Kingdom, United States) (Chemical Information Services, 1995). 

According to the 1981-83 National Occupational Exposure Survey (NOES, 1997), approximately 6000 workers in the United States were potentially exposed to A-vinyl-2-pyrrolidone (see General Remarks). 

No international guideline for A-vinyl-2-pyrrolidone in drinking-water has been established (WHO, 1993). 

Groups of 30 male and 30 female Sprague-Dawley rats, 37-39 days of age, were administered A-vinyl-2-pyrrolidone (purity, 99.9%) by whole-body inhalation at concen-... 

A-Vinyl-2-pyrrolidone was tested for carcinogenicity in one experiment in rats by... 

A -Vinyl-2-pyrrolidone metabolites and polyvinyl pyrrolidone are excreted mainly in urine. Inhalation of low concentrations of A -vinyl-2-pyrrolidone by rats can cause nasal cavity inflammation, atrophy of olfactory epithelium and hyperplasia of the basal cells of the respiratory and olfactory epithelium. In humans and experimental animals, polyvinyl pyrrolidone accumulates in vacuoles of cells of many organs and, in humans, may be accompanied by pulmonary fibrosis and pneumonia. There have been no genetic toxicity studies with either compound. 

There is limited evidence for the carcinogenicity of A -vinyl-2-pyrrolidone in experimental animals. 

A possible reaction course comes to mind. The A-vinyl-2-pyrrolidone also possesses at the oxygen a nucleophilic center which could attack the electrophilic carbene carbon and could release the carbene ligand from the metal. The intermediate product formed—irrespective of whether it is an open chain or a six-membered ring—then undergoes a heterolytic fragmentation by splitting similar to that observed by Grob (84) (Fig. 7). 

Fig. 7. Hypothesis concerning the course of the reaction during the treatment of pen tacarbonylfmethoxy (phenyl) carbene]chromium (0) with A-vinyl-2-pyrrolidone and -substituted iV-vinylpyrrolidones under normal pressure.

Ethylene dimethacrylate-methyl methacrylate Ethylene dimethacrylate 1,3-Butylene dimethacrylate Acrylonitrile a-Chloroacrylonitrile Vinyl acetate Styrene Vinyltoluene Divinylbenzene A -Vinyl-2-pyrrolidone 4-Vinylpyridine Diallyl phosphite Triallyl phosphate Butenediol... 

Regarding the initiation process of polymerization, it can be started by y-radiation. It is a method that has been used for the synthesis of hydrogels of PEO as well as hydrogels based on vinyl monomers " in this latter case, azo-compounds such as 2,2-azo-isobutyroni-trile (AIBN)f or 2,2 -azobis (2-amidine-propane) dihydrochloride or V-SO, and aqueous salt solutions such as aqueous ammonium peroxodisulfate are also used. Among the monomers most used in the preparation of hydrogels through free-radical polymerization are 2-hydroxyethyl methacrylate (HEMA) and A-vinyl-2-pyrrolidone (VP). ... 

As we have seen in Figure 5 the local densities of state in ordered 1 1 alloys AB are different on the two different sites (one site for constituent A, the other for B). It is easy to understand that in a disordered alloy of the same overall composition, there will be many different sites for each of the constituents, depending on, e.g., the composition of the surrounding layer of atoms. Indeed, the NMR lines in alloys are always broader than those in pure metals. A further complication is added when we make small particles of disordered alloys. The catalytic activity of Pti- Pd protected by films of poly(A-vinyl-2-pyrrolidone) (PVP) varies strongly with composition [75]. One would like to study both metals by NMR, but unfortunately lo pd NMR is very difficult and has not been attempted on small particles. Some information on small palladium particles is available from susceptibility measurements on catalysts [76] and on cluster molecules [77]. In both cases it was concluded that the susceptibility of the surface atoms is less than that of the bulk, just as is found for platinum particles from their NMR data. It is then reasonable to assume that in these systems the Pd susceptibility heals back when going from the surface to the interior, and that also for Pti Pdx particles an expression like Eq. (17) is valid. 

Guthrie and co-workers have used an anthraquinone dye to photosensitize the grafting of A -vinyl-2-pyrrolidone onto cotton. The dye (10) sensitizes in two... 

Fluorescence polarization studies have also provided valuable information on excimer formation, energy migration, and molecular mobility in polymers. The role of hydrophobicity was analysed for mixtures of poly(methacrylic acid) and poly(A-vinyl-2-pyrrolidone) in solution, and the motion of 8-anilino-l-naphthalenesulphonic acid covalently bound to poly(methacrylic acid) has been... 

Kitano S, Koyama Y, Kataoka K, Okano T, Sakurai Y. A novel drug delivery system utilizing a glucose responsive polymer complex between polyCvinyl alcohol) and poly(A -vinyl-2-pyrrolidone) with a phenylboronic acid moiety. J Contr Rel 1992 19 162-170. 

Considerable potential is associated with the catalytic applications of Ag NPs, and there are several reports on the research in this field. The oxidation of ethylene, catalyzed by polyacrylic acid (PAA)-Ag nanoclusters, was performed in glycol under 1 atm of ethyleneioxygen. Products were identified as ethylene oxide by analysis with gas chromatography. Ag nanoclusters thus prepared had higher catalytic activity than a commercial silver catalyst. The oxidation rate catalyzed by the PAA-Ag nanoclusters remarkably inaeased with inaeasing reaction temperature. PAA-protected Ag nanoclusters had much higher activity than poly(A-vinyl-2-pyrrolidone)-protected particles at high temperatures. The addition of both caesium and rhenium ions eminently increased the catalytic activity of PAA-Ag nanoclusters (Shiraishi and Toshima 2000, Toshima et al. 2001). 

AC1 Acikses, A., Kaya, I., Sezek, U., and Kirilrrris, C., Syrrthesis, characterization and thermodynamic properties of poly(3-mesityl-2-hydroxypropyl methacrylate-co-A-vinyl-2-pyrrolidone). Polymer, 46, 11322, 2005. 

DH Dincer, S., Rzaev, Z.M.O., and Piskirr, E., Synthesis and characterization of stimrrli-responsive poly(A -isopropylacrylarrride-co-A-vinyl-2-pyrrolidone), J. Polym. Res., 13, 121, 2006. 

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