水-乙醇二元体系共沸混合物的热力学研究

用全自动低温绝热量热计测定了水、乙醇以及水和乙醇组成的共沸混合物在不同温区的摩尔热容Cp,m. 建立了共沸混合物Cp,m与温度T的函数关系.结果表明,水和乙醇组成的共沸混合物在98.496 K发生玻璃态转化,在158.939 K 和270.95 K发生固-液相变.获得了其相应的相变焓和相变熵.计算了以298.15 K为基准的该共沸混合物的热力学函数和超额热力学函数.     

Gamma-hydroxyalkenals are oxidatively cleaved through Michael addition of acylperoxy radicals and fragmentation of intermediate beta-hydroxyperesters

Oxidative cleavage of arachidonate (C(20)) and linoleate (C(18)) phospholipids generates truncated C(8) or C(12) gamma-hydroxyalkenal phospholipids as well as C(5) or C(9) carboxyalkanoate phospholipids, which are abundant in atherosclerotic plaques. The gamma-hydroxyalkenals promote foam cell formation by scavenger receptor CD36-mediated endocytosis. The carboxyalkanoates are potent regulators of endothelial cell functions that may promote atherogenesis. We now report an unexpected biosynthetic interconnection; the carboxyalkanoates can be generated through oxidative cleavage of the gamma-hydroxyalkenals with the loss of three carbons. This unprecedented transformation is shown to involve Michael addition of an acylperoxy radical and fragmentation of the resulting beta-hydroxyperester.     

Pre-Column Derivatization of Amines with 1,2-Benzo-3,4-Dihydrocarbazole-9-Isopropyl Chloroformate Followed by LC-Fluorescence and LC-APCI-MS

A pre-column derivatization method for the sensitive determination of amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl chloroformate (BCIC-Cl) followed by high-performance liquid chromatography with fluorescence detection has been developed. Identification of derivatives is carried out by high performance liquid chromatography/atmospheric pressure chemical ionization (LC-APCI-MS-MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent is replaced by 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl functional group, which results in a sensitive fluorescence derivatizing reagent BCIC-Cl. BCIC-Cl can easily and quickly label amines. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography and show an intense protonated molecular ion corresponding m/z [MH]⁺ under APCI in positive-ion mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 260 corresponding to the cleavage of CH₂-OCO bond. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0–10.0. Maximal yields close to 100% are observed with a 3 to 4-fold molar reagent excess. In addition, the detection responses for BCIC derivatives are compared with those obtained using CEOC and FMOC as derivatization reagents. The ratios of I_BCIC/I_CEOC and I_BCIC/I_FMOC are, respectively, 1.23–3.14 and 1.25–3.08 for fluorescent (FL) responses (here, I is relative fluorescence intensity). Separation of the derivatized amines had been optimized on reversed-phase Eclipse XDB-C₈ column. Detection limits are calculated from 1.0 pmol injection, at a signal-to-noise ratio of 3, are 10.6–37.8 fmol. The mean interday accuracy ranges from 94 to 105% for fluorescence detection with the largest mean %CV<7.5. The mean interday precision for all standards is < 6.0% of the expected concentration. Excellent linear responses are observed with coefficients of > 0.9997. Revised: 12 December 2005 and 13 Febrauary 2006     

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.     

Novel Chiral Aminophosphine Ligand:Synthesis and Application in Saymmetric Catalytic Hydrogenation Reaction

A new chiral aminophosphine ligand 6,6′-dimethoxy-2,2′-bis(diphenylphosphinoamino)biphenyl(DMBDPPABP) was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its dervatives.The effects of solvent and reaction temperature on enantioselectivity were also studied.     

Total synthesis of crotophorbolone

As a natural diterpenoid, crotophorbolone possesses a challenging trans,trans-5/7/6 framework decorated with six contiguous stereogenic centers and is structurally and biogenetically related to tigliane-type diterpenoids with intriguing bioactivities such as phorbol and prostratin. Based on the convergent strategy, we completed an eighteen-step total synthesis of crotophorbolone starting from (−)-carvone and (+)-dimethyl-2,3-O-isopropylidene-l-tartrate. The key elements of the synthesis involve expedient installation of the six-membered ring and the five-membered ring with multiple functional groups at an early stage, cyclization of the seven-membered ring through alkenylation of the ketone between the five-membered ring and the six-membered ring, functional group-sensitive ring-closing metathesis and final selective introduction of hydroxyls at C₂₀ and C₄.

Convergent total synthesis of crotophorbolone was accomplished in 18 longest linear steps. Observation of unexpected thermodynamic stability of a cis,trans-5/7/6 tricycle would benefit synthetic design of tigliane- and daphnane-related diterpenoids.     

Phase behaviour and microstructures of microemulsions (I)

By the orthogonal design, the optimal formation conditions for the middle-phase microemulsions in the system dioctadecyldimethylammonium chloride (DODMAC)/ sodium dodecyl sulfate (SDS)/n-butanol/n-hep-tane/brine were obtained as follows: W_DODMAC: W_SDS = 1:4-1:5,C _π-butanol (%) = 11.0-12.0, andC _NaCl (%) = 3.25 Investigations have been made on the effects of the concentrations of NaCl and n-butanol (l.0%-14.0%), the ratios ofWDODMAC: to W_SDS, and the kinds of alcohols (n-propanol, n-butanol, and n-pentanol) on the formation, the phase behaviour, the ultralow interfacial tensions, the optimal salinity (S^*), and the length of salinity (δS). Some rules and data were worked out about the formation and characteristics of the middle-phase microemulsions. The mi-crostructures of the middle-phase microemulsions were also studied by using FT-IR, ESR, and freeze fracture electron microscopy techniques. The results from the three methods show that the microstructures of the middlephase mi-croemulsions undergo the change from O/W to bicontinuous (B.C.) and to W/O. The distribution rule of the orga-nized molecule assemblies in the middle-phase microemulsions is conducible to constructing the model of microemulsion systems, to recognizing the microstructures of the middle-phase microemulsions, and to setting forth the relationship between the microstructures and macro-properties of rnicroemulsions. Project supported by the Niltional Natural Science Foundation of China and the Chinese Postdoctoral Science Foundation.     

超声辐射下某些含官能团化合物与二氯卡宾的反应

超声辐射在有机反应中的应用日趋广泛。我们曾报道了超声辐射与相转移催化相结合产生二氯卡宾和二溴卡宾的方法及其与烯烃加成反应的结果。该法比单纯使用相转移催化剂或超声辐射更为可取。本文进一步将它用于二氯卡宾与某些含官能团化合物的反应,考察超声辐射的影响。反应是在固-液两相条件下进行的,即以粉末状氢氧化钠为碱,氯仿过量兼作溶剂。结果表明,超声辐射对各类化合物反应的影响有相当明显的差异。     

新型陶瓷材料的光激励发光性质研究

针对以往电子俘获光存储材料存在的问题，利用高温固相反应发制备了一种Eu^2 掺杂的氟氧化物玻璃陶瓷，研究表明在该材料中具有光激励发光(PSL)特性，并可用于电子俘获光存储。XRD分析表明该材料含有大量的BaF2微晶。根据其与BaF2相似的发光特性，推断玻璃陶瓷的PSL有可能来源于微晶中Eu^2 的5d-4f发射。但是决定光激励发光过程中的电子(空穴)陷阱的存在方式、电子迁移途径都有待进一步探讨的问题。与传统的BaFCl：Eu相比，这种材料的光激励发光衰减速度较慢。     

用TMS—2型热机分析仪测量热释蠕变

对已经商品化的Perkin-Elmer TMS-2型热机分析仪进行改进,用来测量聚合物材料的热释蠕变行为。按照7SCr分步加载的程序,用弯曲法测量了-83～300℃温度范围内低密度聚乙烯的玻璃化转变松弛过程,并从TSCr谱上计算其相应的分子参数,实验结果与用扭转的TSCr方法所得结果相等,因此这是一种研究聚合物材料松弛行为的方便可行的技术。