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71.
Oxymethylene dimethyl ethers (OMEn; CH3(‐OCH2‐)nO‐CH3, n=3–5) are a novel class of sustainable synthetic fuels, which are of increasing interest due to their soot‐free combustion. Herein a novel anhydrous OMEn synthesis route is presented. Catalyzed by trimethyloxonium salts, dimethoxymethane takes up monomeric gaseous formaldehyde instantaneously and forms high purity OMEn at temperatures of 25–30 °C. This new anhydrous approach using molecular formaldehyde and catalytic amounts of highly active trimethyloxonium salts represents a promising new step towards a sustainable formation of OMEn emanating from CO2 and H2.  相似文献   
72.
The conjugation of cymantrene CpMn(CO)(3) to cell-penetrating peptide hCT(18-32)-k7 alters the intracellular distribution in MCF-7 cells compared to the unmodified peptide, as visualized by fluorescence microscopy, and leads to an increased nuclear accumulation; the peptide and cymantrene compound themselves are not toxic, but the bioconjugate shows a significant cytotoxicity with an IC(50) value of 36 micromol l(-1).  相似文献   
73.
Hydrogallation Reactions Involving the Monoalkynes H5C6‐C≡C‐SiMe3 and H5C6‐C≡C‐CMe3cis/trans Isomerisation and Substituent Exchange Phenyl‐trimethylsilylethyne, H5C6‐C≡C‐SiMe3, reacted with different dialkylgallium hydrides, R2Ga‐H (R = Me, Et, nPr, iPr, tBu), by the addition of one Ga‐H bond to its C≡C triple bond (hydrogallation). The gallium atoms attacked selectively those carbon atoms, which were also attached to trimethylsilyl groups. The cis arrangement of Ga and H across the resulting C=C double bonds resulted only for the sterically most shielded di(tert‐butyl)gallium derivative, while in all other cases spontaneous cis/trans rearrangement occurred with the quantitative formation of the trans addition products. The diethyl compound Et2Ga‐C(SiMe3)=C(H)‐C6H5 ( 2 ) gave by substituent exchange the secondary products EtGa[C(SiMe3)=C(H)‐C6H5]2 ( 7 , Z,Z) and Ga[C(SiMe3)=C(H)‐C6H5]3 ( 8 ). Interestingly, compound 8 has two alkenyl groups with a Z configuration, while the third C=C double bond has the cis arrangement of Ga and H (E configuration). The reversibility of the cis/trans isomerisation of hydrogallation products was observed for the first time. tert‐Butyl‐phenylethyne gave the simple addition product, R2Ga(C6H5)=C(H)‐CMe3 ( 9 ), only with di(n‐propyl)gallium hydride.  相似文献   
74.
The study explored the compatibility between the main product of Portland cement hydration and the main product of the alkali activation of fly ash: C–S–H and N–A–S–H gels, respectively. Both gels were synthesized with laboratory reagents at different pH values. Blends of the two were synthesized as well, using the sol–gel procedure. All the gels were characterized with Fourier transform IR spectroscopy (FTIR). The gels synthesized with this procedure were shown to precipitate together with a silica-rich gel. In addition, the pH level was found to play a determinant role in both C–S–H and N–A–S–H gel synthesis. The C–S–H gel is the major phase formed at pH > 11 and N–A–S–H gel for pH > 12. The results relating to the joint synthesis of the two (C–S–H and N–A–S–H) gels were not conclusive. Technique used for the characterization failed to differentiate between them in the blended material.
Ines García-LodeiroEmail:
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75.
Rhizopus oryzae lipase (ROL) was immobilized by adsorption onto oxidized cellulose fibers and regenerated films. The maximum adsorption level increases with the raise in the amount of carboxylic groups on cellulose surface confirming that adsorption is being governed mainly by electrostatic interaction between the enzyme and the substrate. This hypothesis was further confirmed by zeta-potential measurements showing a decrease in the zeta-potential of the fibers after enzyme adsorption. XPS analysis showed an intensification of the N 1s peak attesting the presence of the enzyme on the surface. The effect of temperature, pH and solvent polarity on the immobilized enzyme activity and stability was investigated. The catalytic esterification of oleic acid with n-butanol has been carried on using hexane as an organic solvent. A high conversion yield was obtained (about 80%) at 37 degrees C with a molar ratio of oleic acid to butanol 1:1 and 150IU immobilized lipase. The adsorption achieved two successive cycles with the same efficiency, and started to lose its activity during the third cycle.  相似文献   
76.
The (1)H and (13)C NMR chemical shifts and coupling constants of a series of organoarsenic compounds were calculated with DFT methods and compared with available experimental spectra. We show that non-relativistic methods successfully model the NMR spectra of these molecules; relativistic spin-orbit effects are small but appreciable for (13)C shifts, and their inclusion is beneficial. Application of the same methods of calculation to the intriguing natural polyarsenic compound arsenicin A allowed several viable alternative structures to be ruled out and thereby confirmed the previously suggested adamantane-like structure of arsenicin A. These results not only reinforce the known predictive power of DFT NMR calculations, but also open the way for the investigation of other naturally occurring molecules with unusual structures outside the scope of empirical methods.  相似文献   
77.
Sahli  Ines  Ghodbane  Ouassim  Abdellaoui  Mohieddine 《Ionics》2016,22(10):1973-1983

The elaboration of LaZr2Cr4Ni5-based intermetallic compound was performed by mechanical alloying from LaNi5 and ZrCr2 precursors and characterized as active materials of negative electrodes in nickel-metal hydride (Ni-MH) batteries. The effect of the milling duration on the phase composition was investigated. The structural properties of the formed phases were determined by X-ray diffraction and quantified from the Rietveld refinement data. The increase of the milling time up to 40 h leads to the highest abundance of the LaZr2Cr4Ni5 phase, estimated at a weight content of 60.6 %, and a complete elimination of the LaNi5 intermetallic precursor. The chronopotentiometry, cyclic voltammetry, and chronoamperometry techniques were applied to characterize the electrochemical behavior of prepared LaZr2Cr4Ni5-based compounds. The maximum discharge capacity was 152 mAh g−1, and a high electrochemical stability was obtained in the alkaline solution. The value of the hydrogen diffusion coefficient is equal to 2.1 × 10−8 cm2 s−1, reflecting an appropriate electrochemical hydrogenation kinetic in the LaZr2Cr4Ni5-based compounds.

  相似文献   
78.
In an earlier publication (J. Am. Chem. Soc. 2002 , 124, 7111) we showed that polymeric cationic [Ag(P4S3)n]+ complexes (n=1, 2) are accessible if partnered with a suitable weakly coordinating counterion of the type [Al(ORF)4]? (ORF: poly‐ or perfluorinated alkoxide). The present work addresses the following questions that could not be answered in the initial report: How many P4S3 cages can be bound to a Ag+ ion? Why are these complexes completely dynamic in solution in the 31P NMR experiments? Can these dynamics be frozen out in a low‐temperature 31P MAS NMR experiment? What are the principal binding sites of the P4S3 cage towards the Ag+ ion? What are likely other isomers on the [Ag(P4S3)n]+ potential energy surface? Counterion influence: Reactions of P4S3 with Ag[Al{OC(CH3)(CF3)2}4] (Ag[hftb]) and Ag[{(CF3)3CO}3Al‐F‐Al{OC(CF3)3)}3] (Ag[al‐f‐al]) gave [(P4S3)Ag[hftb]] ( 7 ) as a molecular species, whereas [Ag2(P4S3)6]2+[al‐f‐al]?2 ( 8 ) is an isolated 2:1 salt. We suggest that a maximum of three P4S3 cages may be bound on average to an Ag+ ion. Only isolated dimeric dications are formed with the largest cation, but polymeric species are obtained with all other smaller aluminates. Thermodynamic Born–Haber cycles, DFT calculations, as well as solution NMR and ESI mass spectrometry indicate that 8 exhibits an equilibrium between the dication [Ag2(P4S3)6]2+ (in the solid state) and two [Ag(P4S3)3]+ monocations (in the gas phase and in solution). Dynamics: 31P MAS NMR spectroscopy showed these solid adducts to be highly dynamic, to an extent that the 2JP,P coupling within the cages could be resolved (J‐res experiment). This is supported by DFT calculations, which show that the extended PES of [Ag(P4S3)n]+ (n=1–3) and [Ag2(P4S3)2]+ is very flat. The structures of α‐ and γ‐P4S3 were redetermined. Their variable‐temperature 31P MAS NMR spectra are discussed jointly with those of all four currently known [Ag(P4S3)n]+ adducts with n=1, 2, and 3.  相似文献   
79.
A new skeleton of an O-heteroside natural substance named zinolol, the first representative of a new class of aminated hydroxyhydroquinone, has been isolated from the whole plant Anagallis monelli. Its structure has been established by one and two dimensional NMR spectroscopic procedures. Antioxidant, mutagenic, antimutagenic activities were realised and positive results were recorded.  相似文献   
80.
What is the preferred coordination site of CI3+? Recent computational work suggested the iodine atoms of the Lewis acid CI3+ to be more electrophilic than the classically expected carbon atom, e.g. the complex with water is of type I2C-I...OH2+ and not the classically expected I3C-OH2+. If this structure is correct, one may also anticipate reactions of CI3+ as an I+ donor. Thus, we were interested in investigating the chemistry of CI3+ in the room-temperature stable salt [CI3]+[pftb](-) ([pftb](-) = [Al(OC(CF3)3)4]-) with weak nucleophiles that i) mimic water (OEt2) or ii) are electronically deactivated weak nucleophiles (PX3, X = Cl-I; AsI3). One question was: is it possible to obtain iodine-coordinated Lewis acid-base adducts of the CI3+ cation? With Et2O as a base, the cation behaves as a strong Lewis acid and cleaves the ether to give I3C-OEt, C2H4 and [H(Et2O)2]+. By contrast PX3 and AsI3 coordinate to the CI3+ cations and the adducts have classical, carbon-bound ethane-like structures, as proven by X-ray single-crystal diffraction, IR, UV-Vis and NMR spectroscopy. From variable temperature 13C NMR studies, it followed for the I3C-AsI3+ salt that the equilibrium between CI3+ and AsI3 is reversible and temperature dependent in solution. The I3C-PI3+ salt decomposes at room temperature giving PI4+ and C2I4, likely through an iodine coordinated I2C-I[dot dot dot]PI3+ intermediate. Thus CI3+ may also act as an I+ donor. All reactions are in agreement with ab initio quantum chemical calculations at the MP2/TZVPP level and assignments of experimental spectra were aided by quantum chemistry.  相似文献   
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