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31.
Summary Reactions of titanium(IV) isopropoxide with ethyl 1-hydroxycyclohexylacetate, ethyl 2-hydroxy-2-arylpropionate, ethyl 2-hydroxy-2-arylbutyrate and ethyl 2-hydroxy-2-arylhydrocinnamate have been studied in dry benzene in different molar ratios under strictly anhydrous conditions. The Ti(OPr-i)4-nLn type compounds, where L = hydroxy ester and n = 1 to 4, have been isolated and characterised by elemental analysis, molecular weight, i.r. and n.m.r. spectral studies. These products may be distilled unchanged under reduced pressure.Reprints of this are not available. 相似文献
32.
Single bacterial cells, each expressing a different library variant, were compartmentalized in aqueous droplets of water-in-oil (w/o) emulsions, thus maintaining a linkage between a plasmid-borne gene, the encoded enzyme variant, and the fluorescent product this enzyme may generate. Conversion into a double, water-in-oil-in-water (w/o/w) emulsion enabled the sorting of these compartments by FACS, as well as the isolation of living bacteria cells and their enzyme-coding genes. We demonstrate the directed evolution of new enzyme variants by screening >10(7) serum paraoxonase (PON1) mutants, to yield 100-fold improvements in thiolactonase activity. In vitro compartmentalization (IVC) of single cells, each carrying >10(4) enzyme molecules, in a volume of <10 femtoliter (fl), enabled detection and selection despite the fast, spontaneous hydrolysis of the substrate, the very low initial thiolactonase activity of PON1, and the use of difusable fluorescent products. 相似文献
33.
Shefali Pal Sailendra Nath Poddar Gurucharan Mukherjee 《Transition Metal Chemistry》1994,19(4):449-452
Summary Nickel(II) and palladium(II) complexes of the 1,3-di(o-aminophenylthio) propane (H2L1) and 1,2-di(o-aminophenylthio)xylene (H2L2) ligands have been prepared and characterized. The hydrobromide salt of H2L1 gave a 12 ligand-metal complex of PdII, whereas free H2L1 formed the usual 1:1 species. The reaction of Na2PdCl4 with H2L2 resulted in S,S-dealkylation of the ligand and formation of a mononuclear complex of the corresponding thiol, i.e. 2-aminobenzenethiol. NiCl2, NiBr2 and Ni(ClO4)2 did not react directly with H2L2. NiII is a fairly hard ion and therefore does not coordinate to the soft thioether moiety in H2L2 in the absence of soft anions which symbiotically motivate NiII to act as a soft acceptor. It thus does not react with H2L2 in the presence of hard ions such as Cl–, Br- and ClO
4
–
, but, the in situ reaction of the constituents produced the tetrahedral NiII complex, contrary to earlier reports of similar types of octahedral species. 相似文献
34.
The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride. 相似文献
35.
Kundu S Pal A Ghosh SK Nath S Panigrahi S Praharaj S Pal T 《Inorganic chemistry》2004,43(18):5489-5491
Ligands with a beta-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes from aqueous HAuCl(4) solution. Evolution of stable gold nanoparticles follows first order (k approximately equal to 10(-2) min(-1)) kinetics with respect to Au(0) concentration. Growth of particles of different shapes (spherical or triangular or hexagonal) goes hand in hand under the influence of different beta-diketones, which have excellent capping and reducing properties. Chlorine insertion was observed to take place in the beta-diketone skeleton. 相似文献
36.
Photoirradiation at >300 nm of aqueous suspensions of several natural crystal specimens and synthesized crystallites of mercury(II) sulfide (HgS) induced deaminocyclization of optically active or racemic lysine into pipecolinic acid (PCA) under deaerated conditions. This is the first example, to the best of our knowledge, of photoinduced chemical reactions of natural biological compounds over natural minerals. It was found that the natural HgS crystals had activity higher than those of synthesized ones but lower than those of other sulfides of transition metals, e.g., CdS and ZnS, belonging to the same II-IV chalcogenides. In almost all of the photoreactions, decompostion of HgS occurred to liberate hydrogen sulfide (H(2)S) and Hg(2+), and the latter seemed to have undergone in-situ reductive deposition on HgS as Hg(0) after a certain induction period (24-70 h) during the photoirradiation, as indicated by the darkened color of the suspensions. The formation of PCA, presumably through combination of oxidation of lysine and reduction of an intermediate, cyclic Schiff base, could also be seen after a certain induction time of the Hg(0) formation. This was supported by the fact that the addition of small amount of Hg(2+) (0.5 wt % of HgS) increased the PCA yield by almost 2-fold. We also tried to elucidate certain aspects of the plausible stereochemical reactions in relation to the chiral crystal structure of HgS. Although, in some experiments, slight enantiomeric excess of the product PCA was observed, the excess was below or equal to the experimental error and no other supporting analytical data could not be obtained; we cannot conclude the enantiomeric photoproduction of PCA by the natural chiral HgS specimen. 相似文献
37.
Tarducci C Badyal JP Brewer SA Willis C 《Chemical communications (Cambridge, England)》2005,(3):406-408
A substrate-independent method for Diels-Alder chemistry at solid surfaces is described for the first time. 相似文献
38.
O. M. Maikut R. G. Makitra E. Ya. Pal’chikova 《Russian Journal of General Chemistry》2007,77(12):2198-2202
The solubility of organic liquids in water and of water in organic liquids is primarily determined by the capability of organic liquids for hydrogen bonding. Adequate generalization of the solubility data is possible only with multiparameter equations taking also into account other properties of organic components, including the cohesion and molar volume. 相似文献
39.
The Ramanujan Journal - This paper provides elementary proofs for several types of congruences involving multipartitions and self-convolutions of the divisor function. Our computations use... 相似文献
40.