硅胶担载四核羰基钴催化剂的EXAFS和IR研究

本文以透射法EXAFS和IR等手段研究了四核羰基钴金属簇Co_4(CO)_(10)(PPh)_2担载在SiO_2上以后及用于烯烃醛化反应前后的变化,确定了相应的结构参数并探讨了催化活性与结构的关系。     

Solvent extraction of uranium(VI) with benzyloctadecyldimethylammonium chloride (BODMAC) from highly concentrated chloride solution

The ²²²Rn emanation fraction (EF) released from the technically enhanced naturally occurring radioactive material (TE-NORM) wastes at certain sites of petroleum and gas production was determined. The samples were analyzed by γ-ray spectrometry to determine the activity concentration of the ²²⁶Ra content, of which the ²²²Rn emanation fraction was calculated. The results showed that the ²²²Rn emanation fraction differs in the oil and gas production sites and it is independent of the activity concentration of ²²⁶Ra. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparison between the SBR vulcanizates reinforced by magnesium methacrylate added directly or prepared in situ

The styrene-butadiene rubber (SBR) cured by dicumyl peroxide was reinforced by magnesium methacrylate [Mg(MAA)₂], which was added into SBR directly or prepared in situ in SBR through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA). The experimental results show that the SBR vulcanizates reinforced by Mg(MAA)₂ prepared in situ have better mechanical properties than those reinforced by Mg(MAA)₂ added directly. The SBR vulcanizates with Mg(MAA)₂ prepared in situ are semi-transparent, but those with Mg(MAA)₂ added directly are opaque. The Fourier transform infrared analysis shows that the polymerization conversion of Mg(MAA)₂ in the SBR vulcanizates with Mg(MAA)₂ prepared in situ is much higher than that in the SBR vulcanizates with Mg(MAA)₂ added directly. The scan probe microscopy photographs show that the particles in the SBR vulcanizates with Mg(MAA)₂ prepared in situ are much finer and disperse more evenly than that in the SBR vulcanizates with Mg(MAA)₂ added directly.     

Liquid chromatographic enantiomer resolution of N-fluorenylmethoxycarbonyl alpha-amino acids and their ester derivatives on polysaccharide-derived chiral stationary phases

The liquid chromatographic enantiomer separation of N-fluorenylmethoxycarbonyl (FMOC) protected alpha-amino acids and their ethyl ester derivatives was performed on polysaccharide-derived chiral stationary phases, Chiralcel OD, Chiralpak AD, and Chiralpak AS. In general, Chiralcel OD and Chiralpak AD showed good performance for resolution of N-FMOC alpha-amino acids and their ethyl esters, respectively. All investigated N-FMOC alpha-amino acid enantiomers were baseline separated on Chiralcel OD or Chiralpak AD, whereas N-FMOC alpha-amino acid ethyl ester enantiomers were baseline resolved (alpha = 1.15-3.03) on Chiralpak AD, except for two analytes. The L-enantiomers of all examined FMOC alpha-amino acid ethyl ester derivatives are preferentially retained on Chiralpak AD, while the elution orders of the other enantiomer separations are not consistent.     

Synthesis and Structure of [DB24C8)Na][Cd(SCN)3. Formation of a novel linear Cd...Cd...Cd chain with a mer-CdN3S3 coordination confirmation and new coiled [(DB24C8)Na]+ cation

We report herein a novel coordination solid, [(DB24C8)Na][Cd(SCN)3] (6) (DB24C8 denotes dibenzo-24-crown-8), which exhibits a new type of [Cd(SCN)3-]infinity chain with two unusual stereochemical characteristics: (1) a mer-CdN3S3 coordination and (2) a linear Cd chain with a Cd...Cd...Cd angle of 180 degrees. In addition, the [(DB24C8)Na]+ monocation adopts a new structural type-a coiled structure-for the combination of crown ether DB24C8 and alkali metal Na+. The title compound crystallizes in a monoclinic unit cell of C2/c space group symmetry with lattice parameters a = 16.110(8) A, b = 20.380(5) A, c = 11.01(1) A, beta = 119.87(3) degrees, and Z = 4. The arrangement of the [Cd(SCN)3-](infinity) chains in the crystal lattice in the title compound is approximately hexagonal, creating triangular channels which are filled with [(DB24C8)Na]+ monocations. It was previously reasoned by us that the coiled [(DB24C8)Na]+ monocation, which lacks inversion or mirror symmetries, should enhance the tendency for the formation of the noncentrosymmetric space group of the title crystal, making it a potential second-order nonlinear optical crystal. Interestingly, however, the title compound crystallizes in a centrosymmetric space group (C2/c) and gives rise to no second harmonic generation (SHG). Previously known [Cd(SCN)3-](infinity) chains adopt fac-CdN3S3 coordination and a zigzag Cd chain configuration with a Cd...Cd...Cd angle of 165 degrees. The zigzag chains can align in either parallel or antiparallel fashion, resulting in efficient or no SHG effects, respectively. The linear Cd.Cd.Cd chain configuration observed in the title compound, on the other hand, makes it indistinguishable between parallel and antiparallel alignments. It is concluded that, to ensure the formation of noncentrosymmetric space groups, it is necessary to employ optically pure chiral cations as spacers and/or controllers. Furthermore, to enhance the nonlinear optical responses, [Cd(SCN)3-]infinity chains with fac-CdN3S3 coordination and parallel alignments of the zigzag Cd chains should be used.     

Interface characteristics in diffusion bonding of Fe3Al with Cr18-Ni8 stainless steel

Fe3Al and Cr18-Ni8 stainless steel were diffusion-bonded in vacuum and a Fe3Al/Cr18-Ni8 interface with reaction layer was formed. Microstructure in the reaction layer at Fe3Al/Cr18-Ni8 interface was analyzed by means of scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The growth of reaction layer with heating temperature (T) and holding time (t) was researched. The results indicate that FeAl, Fe3Al, Ni3Al, and alpha-Fe (Al) solid solution are formed in the reaction layer. These phases are favorable to promote the element diffusion and to accelerate the formation of the reaction layer at Fe3Al/Cr18-Ni8 interface. The growth of reaction layer obeys the parabolic law and its thickness (X) is expressed by X2 = 7.5 x 10(-4)exp(-83.59/RT)(t - t0).     

A delicate balance of energetics. Subtleties associated with alpha-ketol-based bridge migration to afford 9-keto-10beta-p-methoxybenzyloxytaxanes

The feasibility of the title reaction has been pursued for the purpose of advancing a concise total synthesis of Taxol. Of the two closely related series examined, the first featured an exo-methylene group at C4. The second consisted of an alpha-epoxide at that site. Strikingly, the olefinic construct proved inert to attempted alpha-ketol rearrangement. In contrast, the oxiranyl derivative isomerized smoothly. The reaction sequence associated with arrival at taxane 18 is short (15 steps from a D-camphor derivative) and notably efficient. The thermodynamic issues that are raised by this investigation have been clarified by an assessment of molecular mechanics-derived (MM3) steric energy calculations.     

八—4—(四氢糠氧基)双酞菁衍生物钕(Ⅲ)、铕(Ⅲ)的合成和LB膜的气敏性

八—４—（四氢糠氧基）双酞菁衍生物钕（Ⅲ）、铕（Ⅲ）的合成和ＬＢ膜的气敏性张引＊辛春梅王丹（吉林省教育学院化学系，长春１３００２２）梁冰洁＊＊陈文启席时权（中科院长春应用化学研究所，长春１３００２２）关键词：希土双酞菁衍生物ＬＢ膜气敏性荧光性紫外可见...     

N-（4＇-取代嘧啶-2＇-基）-取代苯氧基磺酰脲的合成及除草活性

光谱;N-（4＇-取代嘧啶-2＇-基）-取代苯氧基磺酰脲的合成及除草活性