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51.
Intermolecular Stetter reaction of aromatic aldehydes with (E)-(2-nitrovinyl)cyclohexane catalyzed by thiazolium A has been developed. The reaction rate and efficiency are profoundly impacted by the presence of thiourea B. The reaction affords moderate to good yields of the Stetter product. Some factors influencing yield were discussed. 相似文献
52.
Metal Oxide Assisted Preparation of Core–Shell Beads with Dense Metal–Organic Framework Coatings for the Enhanced Extraction of Organic Pollutants 下载免费PDF全文
Mateo del Rio Dr. Carlos Palomino Cabello Veronica Gonzalez Dr. Fernando Maya Dr. Jose B. Parra Dr. Victor Cerdà Dr. Gemma Turnes Palomino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11770-11777
Dense and homogeneous metal–organic framework (MOF) coatings on functional bead surfaces are easily prepared by using intermediate sacrificial metal oxide coatings containing the metal precursor of the MOF. Polystyrene (PS) beads are coated with a ZnO layer to give ZnO@PS core–shell beads. The ZnO@PS beads are reactive in the presence of 2‐methylimidazole to transform part of the ZnO coating into a porous zeolitic imidazolate framework‐8 (ZIF‐8) external shell positioned above the internal ZnO precursor shell. The obtained ZIF‐8@ZnO@PS beads can be easily packed in column format for flow‐through applications, such as the solid‐phase extraction of trace priority‐listed environmental pollutants. The prepared material shows an excellent permeance to flow when packed as a column to give high enrichment factors, facile regeneration, and excellent reusability for the extraction of the pollutant bisphenol A. It also shows an outstanding performance for the simultaneous enrichment of mixtures of endocrine disrupting chemicals (bisphenol A, 4‐tert‐octylphenol and 4‐n‐nonylphenol), facilitating their analysis when present at very low levels (<1 μg L?1) in drinking waters. For the extraction of the pollutant bisphenol A, the prepared ZIF‐8@ZnO@PS beads also show a superior extraction and preconcentration capacity to that of the PS beads used as precursors and the composite materials obtained by the direct growth of ZIF‐8 on the surface of the PS beads in the absence of metal oxide intermediate coatings. 相似文献
53.
Miscible blends of poly(ethylene oxide) with brush copolymers of poly(vinyl alcohol)‐graft‐poly(l‐lactide) 下载免费PDF全文
Ainhoa Lejardi Jose‐Ramon Sarasua Agustin Etxeberria Emilio Meaurio 《Journal of Polymer Science.Polymer Physics》2016,54(13):1217-1226
Even though poly(ethylene oxide) (PEO) is immiscible with both poly(l ‐lactide) (PLLA) and poly(vinyl alcohol) (PVA), this article shows a working route to obtain miscible blends based on these polymers. The miscibility of these polymers has been analyzed using the solubility parameter approach to choose the proper ratios of the constituents of the blend. Then, PVA has been grafted with l ‐lactide (LLA) through ring‐opening polymerization to obtain a poly(vinyl alcohol)‐graft‐poly(l ‐lactide) (PVA‐g‐PLLA) brush copolymer with 82 mol % LLA according to 1H and 13C NMR spectroscopies. PEO has been blended with the PVA‐g‐PLLA brush copolymer and the miscibility of the system has been analyzed by DSC, FTIR, OM, and SEM. The particular architecture of the blends results in DSC traces lacking clearly distinguishable glass transitions that have been explained considering self‐concentration effects (Lodge and McLeish) and the associated concentration fluctuations. Fortunately, the FTIR analysis is conclusive regarding the miscibility and the specific interactions in these systems. Melting point depression analysis suggests that interactions of intermediate strength and PLOM and SEM reveal homogeneous morphologies for the PEO/PVA‐g‐PLLA blends. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1217–1226 相似文献
54.
Theoretical investigations on the insertion reaction mechanisms of three- membered-ring silylenoid H2 Si Li F with GeH 3R(R = F, OH, NH2) have been systematically carried out by combined density functional theory(DFT) and ab initio quantum chemical calculations. The geometries of all stationary points for these reactions were optimized using the B3 LYP method and then the QCISD method was used to calculate the single-point energies. The calculated results indicate that, there are one precursor complex(Q), one transition state(TS), and one intermediate(IM) which connect the reactants and the products along the potential energy surface. The insertion reactions of three-membered-ring silylenoid with Ge H3 R proceed in a concerted manner, forming H2RSi-Ge H3 and Li F. The calculated potential energy barriers of the three reactions are 29.17, 30.90, and 54.07 k J/mol, and the reaction energies for the three reactions are –127.05, –116.91, and –103.31 k J/mol, respectively. The insertion reactions in solvents are similar to those in vacuum. Under the same situation, the insertion reactions should occur easily in the following order: GeH 3-F GeH 3-OH GeH 3-NH2. The elucidations of the mechanism of these insertion reactions provided a new mode of silicon-germanium bond formation. 相似文献
55.
Lorenzo Milli Dr. Nicola Zanna Andrea Merlettini Matteo Di Giosia Dr. Matteo Calvaresi Prof. Maria Letizia Focarete Prof. Claudia Tomasini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12106-12112
We present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc‐l ‐Phe‐d ‐Oxd‐OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO‐loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO‐loaded hydrogel through π–π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO. 相似文献
56.
Dr. Jeanette E. Stok Dr. Sharon Chow Dr. Elizabeth H. Krenske Clementina Farfan Soto Csongor Matyas Prof. Raymond A. Poirier Prof. Craig M. Williams Prof. James J. De Voss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4408-4412
The cytochromes P450 are hemoproteins that catalyze a range of oxidative C?H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450cam (CYP101A1) and P450cin (CYP176A1)]‐generated arene oxide as a product of in vitro oxidation of tert‐butylbenzene. Computations (CBS‐QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450‐mediated transformations, suggesting that arene oxides can be unstable terminal products of P450‐catalyzed aromatic oxidation that can explain the origin of some observed metabolites. 相似文献
57.
58.
Specific Design of Titanium(IV) Phenolato Chelates Yields Stable and Accessible,Effective and Selective Anticancer Agents 下载免费PDF全文
Sigalit Meker Dr. Ori Braitbard Dr. Matthew D. Hall Prof. Jacob Hochman Prof. Edit Y. Tshuva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9986-9995
Octahedral titanium(IV) complexes of phenolato hexadentate ligands were developed and showed very high stability for days in water solutions. In vitro cytotoxicity studies showed that, whereas tetrakis(phenolato) systems are generally of low activity presumably due to inaccessibility, smaller bis(phenolato)bis(alkoxo) complexes feature high anticancer activity and accessibility even without formulations, also toward a cisplatin‐resistant cell line. An all‐aliphatic control complex was unstable and inactive. A leading phenolato complex also revealed: 1) high durability in fully aqueous solutions; accordingly, negligible loss of activity after preincubation for three days in medium or in serum; 2) maximal cellular accumulation and induction of apoptosis following 24–48 h of administration; 3) reduced impact on noncancerous fibroblast cells; 4) in vivo efficacy toward lymphoma cells in murine model; 5) high activity in NCI‐60 panel, with average GI50 of 4.6±2 μm . This newly developed family of TiIV complexes is thus of great potential for anticancer therapy. 相似文献
59.
Single crystals of a new silicate carbonate, K2Ca[Si2O5](CO3), have been synthesized in a multi-components hydrothermal solution with a pH value close to neutral and a high concentration of a carbonate mineralizer. The new compound has an axial structure (s.g. P6322) with unit cell parameters a = 5.04789 (15), c = 17.8668 (6) Å. Pseudosymmetry of the structure corresponds to s.g. P63/mmc which is broken only by one oxygen position. The structure consists of two layered fragments: one of the type of the mineral kalsilite (KAlSiO4) and the other of the high-temperature soda-like α-Na2CO3, Ca substituting for Na. The electro-neutral layer K2[Si2O5] (denoted K) as well as the layer Ca(CO3) (denoted S) may separately correspond to individual structures. In K2Ca[Si2O5](CO3) the S-K layers are connected together via Ca-O interactions between Ca atoms from the carbonate layer and apical O atoms from the silicate one, and also via K-O interlayer interactions. A hypothetical acentric structure, sp.gr. P-62c, is predicted on the basis of the order-disorder theory. It presents another symmetrical option for the arrangement of K-layers relative to S-layers. The K,Ca-silicate-carbonate powder produces a moderate SHG signal that is two times larger that of the α-quartz powder standard and close to other silicates with acentric structures and low electronic polarizability. 相似文献
60.
Selective Growth and Structural Analysis of Regular MnO Nanooctapods Bearing Multiple High‐Index Surface Facets 下载免费PDF全文
Although numerous morphologies of MnO nanostructures have been reported, an exact structural analysis and mechanistic study has been lacking. In the present study, the formation of regular MnO octapods was demonstrated in a simple procedure, comprising the thermal decomposition of manganese oleate. Because of their structural uniformity, an ideal three‐dimensional model was successfully constructed. The eight arms protruded from the cubic center with tip angles of 38° and surface facets of {311} and {533} with rounded edges. The concentrations of oleate and chloride ions were the determining factors for the octapod formation. Selective coordination of the oleate ions to the {100} faces led to edge growth along the <111> direction, which was then limited by the chloride ions bound to the high‐index surface facets. These structural and mechanistic analyses should be helpful for understanding the complex nanostructures and for tuning their structure‐related properties. 相似文献