Protonated diolefin complexes: Model systems for C?;h activation via metal complexation

On protonation of the diolefin complexes [M(C₅R₅)(diene)] (R = H, CH₃; M = Co, Rh, Ir; diene = 2,3-dimethylbutadiene, 1,3-cyclohexadiene) with HBF₄, cationic species are isolated which, at room temperature, show fluxional behaviour on the NMR time scale. Depending on R and M, three different ground states are observed for these cationic complexes in the NMR spectra at low temperatures. While for M = Ir a classical metal-hydride structure M–H is observed, the Co and Rh complexes show ground states with ‘agostic’ H-bridges M‥H‥C. The protonated species are characterized by ¹H-, ¹³C- and ¹⁰³Rh-NMR spectra. Total line-shape analysis of the ¹H and ¹³C spectra in the 298–154 K range gave the free enthalpies of activation ΔG ^≠ for methyl rotation and 1, 4-H shift in the agostic structures 2b , 2b′ , 2c , and 2c′ . The Rh complexes show the lowest ΔG^± values for the 1,4-H shift, and the strength of the agostic bond appears to decrease in the order CoC₅H₅ > CoC₅Me₅ > RhC₅H₅ > RhC₅Me₅. Only for R = H and M = Rh and in the presence of traces of Lewis bases (H₂O, Pyridine, or acetone), variable amounts of coordinatively saturated allyl complexes competing with the agostic species are observable. Morethan equimolar amounts of basic solvents lead to irreversible deprotonation and recovery of the starting complexes. Stable allyl-halide complexes are formed on reaction with HCI, while protonation with HBF₄, in the presence of CO, gives high yields of complexes [M(CO)(allyl)(C₅R₅)] [BF₄]. The different ground states observed for the protonated complexes and the dynamic behaviour in solution are compared with other hydride-transfer reactions observed in organometallic chemistry, specifically with the β-hydride elimination and the catalytic hydrogenation of olefins.     

Liquid Chromatography-Mass Spectrometry Hyphenation for Exhaustive and Unambiguous Characterization of Polyoxyethylene Surfactants

A rapid, specific and reliable high performance liquid chromatographic (HPLC) assay of sildenafil in pharmaceutical dosage forms has been developed and evaluated. Reversed phase chromatography was conducted using a mobile phase of methanol: water: acetonitrile (60:20:20) v/v/v, pH 6.1, 0.1% glacial acetic acid, and detection at λ 290 nm. The recovery and coefficient of variation from six tablets containing 50 mg of sildenafil were 100.90% and 0.45% respectively. Replicate regression analysis of three standard plots in the concentration range (0.01–0.2) μg mL^?1 obtained on three different days gave a correlation coefficient >0.999 and the coefficient of variation of the slopes <1.5%. The assay was precise within day and between days as indicated by ANOVA test. It is suggested that the proposed HPLC method should be used for routine quality control and dosage form assay of sildenafil citrate. The proposed method was also used to study the stability of sildenafil citrate in different dosage forms of the drug.     

联苯聚醚醚酮酮的合成与性能研究

用亲核取代路线合成了含亚联苯结构的新型聚醚醚酮酮（联苯ＰＥＥＫＫ），并对其基本性能进行了测定。结果表明，联苯ＰＥＥＫＫ的Ｔｍ比聚醚醚酮（ＰＥＥＫ）高７７℃，其Ｔｇ比ＰＥＥＫ的高４１℃，且保持了良好的力学性能，本文还对联苯ＰＥＥＫＫ的晶体结构进行了初步探讨。     

Analysis of functionalized polyisobutylenes by capillary SFC, SEC, HPLC, and CGC-MS after fraction collection

Summary An analytical strategy has been developed for analysis of polyisobutylenes partially functionalized with isothiocyanate groups ( ) by capillary supercritical-fluid chromatography (CSFC), size- exclusion chromatography (SEC), and reversed-phase liquid chromatography (RPLC). Fractions collected from semi-preparative RPLC and SEC were further characterized by capillary GC-MS (gas chromatography coupled with mass spectrometry). Complete characterization of the polymer was achieved by comparing the results obtained from the different techniques. The degree of polymerization and the relative quantity of the different series of macromolecular chains of polyisobutylene were estimated.     

水化Na-蒙脱石和Na/Mg-蒙脱石的分子动力学模拟

利用分子动力学方法(MD)研究了Na-蒙脱石和Na/Mg-蒙脱石层间的补偿阳离子和水分子的结构及扩散性质. 模拟结果表明, 在一定水含量范围内Na-蒙脱石和Na/Mg-蒙脱石表现出不同的膨胀形式, 特别是层间水分子数目在48～72之间时, Na/Mg-蒙脱石的层间距比Na-蒙脱石有较为明显的增大. Na/Mg-蒙脱石两层水化物的层间水分子与Mg2+形成了明显的两层水合壳; 而与Na+只形成了一层平面的水合壳. 在Na/Mg-蒙脱石中, Na+和 Mg2+的扩散方式不同, Na+的扩散范围相对更广, 自扩散系数更大. Na/Mg-蒙脱石比相同水含量下的Na-蒙脱石层间水的自扩散系数小. 由于Mg2+和Na+对层间结构的强烈影响, 从而使有少量Mg2+取代Na+的Na/Mg-蒙脱石与Na-蒙脱石表现出不同的膨胀性质和层间物质的扩散性质.     

4,4'-二氨基二苯醚二苯酮固化环氧树脂/粘土纳米复合材料的研究

采用离子交换法, 用十六烷基三甲基溴化铵处理钙基蒙脱土(MMT), 使蒙脱土的层间距由1.49 nm扩大到2.21 nm, 制备了环氧树脂/ BADK/MMT纳米复合材料, 并用XRD等手段研究了有机蒙脱土在环氧树脂中的插层及剥离行为. 研究结果表明, 蒙脱土含量及环氧树脂与有机土的混合温度和时间均对固化后复合材料的剥离产生影响, 只有在特定条件下才能得到剥离型纳米复合材料.     

聚醚醚酮酮等温结晶动力学的研究

聚醚醚酮酮等温结晶动力学的研究陈艳，王军佐，曹俊奎，那辉，吴忠文（吉林大学化学系，长春，１３００２３）关键词聚醚醚酮酮，等温结晶动力学，差示扫描量热法聚醚醚酮酮（ＰＥＥＫＫ）是在聚醚醚酮（ＰＥＥＫ）基础上开发成功的一种耐热高分子材料。它保持了ＰＥＥＫ...     

流动相组成对有机硒手性化合物拆分的影响

 在自制的涂敷型纤维素 三 (3,5 二甲基苯基氨基甲酸酯 ) (CDMPC)手性固定相上拆分了一些结构相似的有机硒手性化合物 ,详细考察了三元流动相对手性拆分的影响 ,并探讨了溶质分子与手性固定相相互作用的模式。实验结果表明 :在二元流动相中加入极少量的质子性改性剂 (醇 )或非质子性改性剂 (乙腈 ) ,可使溶质的保留和手性拆分发生较大的变化。     

Terpenes and terpene derivatives - XV. [1 ] Synthesis of 4,8-dimethyl-2-(2-methyl-1-propenyl)--1-oxaspiro(4.5]dec-7-ene (“bisabolene oxide”)

Starting from the ketones $\text{3}$ and $\text{4}$ the synthesis of six spiro ethers with an l-oxaspiro[4.5]decane skeleton is described. Five of them, $\text{9a}$,$\text{b}$, $\text{10a}$,$\text{19}$ and $\text{19}$ represent typical partial structures of the sesquiterpenoid spiro ether $\text{1}$. The unambiguous synthesis of $\text{1}$ shows a previous assignment of “'bisabolene oxide“' to structure $\text{1}$ to be wrong.     

含联苯结构聚醚醚酮酮共聚物和共混物的制备及性能研究

聚醚醚酮（PEEK）是八十年代初投入市场的全芳香结构热塑性耐高温特种工程塑料，它的7’。一143“C，Tm一334C“‘，最大结晶度为48％，典型制品结晶度为20％～30％［”．PEEK可用通常的设备成型，其制件、纤维、涂料及复合材料在电子电器、机械设备、交通运输、宇航、原子能工程、军事等领域有广泛的用途［’j．聚醚醚酮酮（PEEKK）是继PEEK之后，由德国Hoechst公司开发出来的又一种全芳香结构热塑性耐高温特种工程塑料［‘j．为了研究该类聚合物的结构和性能的关系，我们在实验室中合成了PEEKK和含联苯结构聚醚醚酮酮（PE－＊…