α-二亚胺钴配合物催化1,3-丁二烯高活性与高顺式-1,4选择性聚合

合成了一系列α-二亚胺钴配合物[ArN=C(Me)-(Me)C=NAr]CoCl₂(Ar=C₆H₅, 3a; 4-MeC₆H₄, 3b; 4-MeOC₆H₄, 3c; 4-FC₆H₄, 3d; 4-ClC₆H₄, 3e; 2-MeC₆H₄, 3f; 2-EtC₆H₄, 3g; 2-ⁱPrC₆H₄, 3h; 2,4,6-Me₃C₆H₂, 3i; 2,6-Et₂C₆H₃, 3j; 2,6-ⁱPrC₆H₃, 3k)和作为对比的吡啶双亚胺二氯化钴配合物(4a), 并用X射线单晶衍射方法研究了配合物3i, 3k和4a的分子结构. α-二亚胺钴配合物在倍半乙基氯化铝的作用下对丁二烯聚合有较高的催化活性,得到的顺式-1,4结构含量达98%,且有较高分子量(M_n≈1×10⁴-1×10⁵)的聚丁二烯. 配体的电子效应影响催化剂的活性及顺式-1,4选择性, 而配体的空间位阻对丁二烯聚合几乎没有影响. 详细研究了聚合时间、聚合温度、烷基铝助催化剂及铝比等条件对丁二烯聚合行为的影响.     

Micelle nano-reactors as mediators of water-insoluble ligand complexation with Cu(II) ions in aqueous medium

Complexation reactions between water-soluble and -insoluble reactants were shown to occur in aqueous media in the presence of normal or reverse surfactant micelles, in significantly higher yields at lower temperatures compared to those achieved in neat organic solvents. The highest yield enhancement in the complexation of novel water-insoluble bis(2-amino-1,3,4-thiadiazolyl)methane and 1,4-bis(2-amino-1,3,4-thiadiazolyl)benzene ligands with Cu(II) ions was achieved in the sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-heptane-water reverse micellar system at the hydration ratio of 15. The results revealed that AOT normal micelles cause a change in the reaction mechanism together with the enhancement of the complex formation. The observed micellar effects were rationalized on basis of the properties of bulk solvents, surfactants and ligands, considering the solvation and hydration ratios of reverse micelles. The results have proved the dependence of complex yield on the amount and accordingly also on the properties of water in the micellar core, indicating that the yield can be maximized by the optimization of the hydration ratio.     

苯甲酰二茂铁修饰碳纳米管糊电极电催化测量蛋氨酸浓度(英文)

A benzoylferrocene modified multi‐wall carbon nanotube paste electrode for the measurement of methionine (MET) concentration is described. MET electrochemical response characteristics of the modified electrode in a phosphate buffer solution of pH 7.0 were investigated by cyclic voltammetry, square wave voltammetry, and chronoamperometry. Under optimized conditions, the square wave voltammetric peak current of MET increased linearly with MET concentration in the range of 1.0×107 to 2.0×104 mol/L. The detection limit was 58.0 nmol/L MET. The diffusion coefficient (D=5.62×106cm2/s) and electron transfer coefficient (α=0.4) for MET oxidation were also determined. The sensor was successfully applied for the measurement of MET concentration in human urine.     

Co2C上CO的程序升温脱附和程序升温表面反应研究

采用CO与金属Co在473K反应400h以上合成了Co₂C样品,采用X射线衍射、透射电镜和CO程序升温还原对样品进行了表征,并采用CO程序升温脱附和CO程序升温表面反应研究了Co₂C对CO的吸附及其加氢活化行为. 结果表明,Co₂C微观结构由体相和表面钝化层两部分组成. 表面钝化层可被CO于477K左右去除. CO在Co₂C上有2个脱附峰,其中低温脱附峰可能源于Co₂C上吸附的CO,而高温脱附峰可能对应于残留于Co₂C晶格内的CO. Co₂C上吸附的CO可与H₂反应生成醇.     

串联双釜连续反应装置中Ru-Co-B/ZrO2上苯选择加氢制环己烯

采用化学还原法制备了苯选择加氢制环己烯催化剂Ru-B/ZrO₂,考察了Cr,Mn,Fe,Co,Ni,Cu和Zn等过渡金属的添加对Ru-B/ZrO₂催化剂性能的影响.结果表明,这些过渡金属的添加均可提高Ru-B/ZrO₂催化剂中的B含量.B的修饰及第二种金属或金属氧化物的集团效应和配位效应导致Ru-B/ZrO₂催化剂活性降低和环己烯选择性升高.当Co/Ru原子比为0.06时,Ru-Co-B/ZrO₂催化剂上反应25min苯转化率为75.8%时,环己烯选择性和收率分别为82.8%和62.8%.在双釜串联连续反应器中和优化反应条件下,Ru-Co-B/ZrO₂催化剂使用419h内苯转化率稳定在40%左右,环己烯选择性和收率分别稳定在73%和30%左右.     

ZSM-5沸石结晶度对乙苯叔丁基化对位选择性的影响(英文)

Highly crystalline ZSM-5 zeolites are important for para-selective alkylation of alkyl aromatics, because they carry few external acid sites for isomerization of p-dialkyl products. Such zeolites (Si/Al = 25, 50, and 75) were synthesized in a fluoride medium between pH 4 and 6. Their crystallinities, crystal sizes, and surface areas were higher than those of a commercial ZSM-5 zeolite. Their para selectivities in alkylation were tested for vapor-phase tert-butylation of ethylbenzene between 200 and 400 °C. As expected, all the catalysts showed more than 90% para selectivity. At 300 °C, ethylbenzene conversion decreased in the order ZSM-5(25, commercial) > ZSM-5(25) > ZSM-5(50) > ZSM-5(75). The catalysts had weak, medium, and strong acid sites, but all the acid sites of ZSM-5(75) were weaker than those of ZSM-5(25) and ZSM-5(50). The high activity of commercial ZSM-5 was caused by its strong acid sites being stronger than those of the synthesized zeolites. Although the activity of the commercial catalyst was higher than those of the present catalysts, the selectivity for 4-t-butylethylbenzene (4-t-BEB) was low. The optimum feed ratio (ethylbenzene:t-butyl alcohol) was 2:1 and the feed rate was 1.65 h?1 for high ethylbenzene conversion and 4-t-BEB selectivity. Time-on-stream studies showed slow catalyst deactivation. Highly crystalline ZSM-5 zeolites are therefore better than a commercial zeolite for para-selective alkylation of alkyl aromatics. They do not require much post-modification for high para selectivity. A fluoride medium is therefore better than an alkaline medium for obtaining highly crystalline para-selective ZSM-5 zeolites.     

A new sesquiterpene from the roots of Vladimiria souliei

A new sesquiterpene, named vladimenal (1), was isolated from the roots of Vladimiria souliei. The structure was elucidated on the basis of spectroscopic analysis.     

Radiation induced chain addition of allylbenzene to 1,4-dioxane

Radiation induced chain addition of allylbenzene to 1,4-dioxane has been studied by IR-, UV-, mass-, NMR- and ESR-spectrometry. Efficiency of the addition depends on the concentration of monomer and it has an optimum atC _monom<0.125M. Apparently, upper concentration limit of the reaction is caused by absorbed energy transfer on the molecule, of monomer followed by energy deactivation. Radiation-chemical yields of the product are 12 and 31 molec./100 eV for 0.125M and 0.07M solution, respectively. The value ofG _prod. is an evidence of chain character of the process.     

Traceability of absorbed dose in photon radiation therapy: from primary standard to patient treatment

The relevant standard quantity for radiation therapy is the absorbed dose to water. This quantity refers to the amount of energy locally absorbed in a small volume of water divided by the mass of this volume. The aim of this paper is to present a short overview on the establishment of traceability to national standards of absorbed doses delivered to patients in radiation therapy. The approach used at LNE-LNHB, the French national metrology laboratory for ionizing radiation, to determine the reference value of absorbed dose to water is presented and the chain of traceability from the reference value to the treatment of the patient is described.     

Synthesis of novel 15-membered macrolide dimers

A series of novel dimers of 15-membered macrolides was synthesized and evaluated.The dimers exhibited excellent activity against erythromycin-susceptible S.pneumonia,but did not show any improved activity against erythromycin-resistant S. pneumoniae encoded by erm gene.