Mesoporous hollow silica spheres as micro-water-tanks in proton exchange membranes

In order to decrease the swelling of Nafion^® and reduce the dependency of proton conductivity on high relative humidity (RH), mesoporous hollow silica spheres were synthesized and dispersed in Nafion matrix as micro-water-tanks in the proton exchange membranes (PEM). The morphologies of MHSi and Nafion/MHSi composite membranes are characterized by SEM and TEM. The effects of MHSi on water uptake, swelling, dehydration rate and proton conductivity of the composite membranes were investigated. The results show that, with a suitable portion of MHSi in the membrane, composite PEMs with enhanced water uptake, reduced swelling and improved proton conductivity are obtained.     

Micro-Raman studies on the conformational behaviors of monosodium glutamate in dehydration process

The conformational behaviors of monosodium glutamate（MSG） in a dehydration process were studied by Micro-Raman spectroscopy in combination with Hartree-Fock calculations using 6-31+G^* method.The dehydration process of the MSG droplet was performed by decreasing the ambient relative humidity（RH）.The intensity ratio of the 935 cm^-1 band to 884 cm^-1 band(I₉₃₅/ I₈₈₄) kept decreasing when RH decreased.By optimizing the geometries with different fixed dihedral angles,the downtrend of(I₉₃₅/ I₈₈₄) is found to be due to the reduction of MSG molecular volume.     

Utilization of perfluoroalkanoate-derived aluminium acetals as the convenient fluorinated aldehyde precursors

Aluminium acetals from the DIBAL partial reduction of perfluoroalkanoates 1 were successfully employed as the convenient and useful fluorinated aldehyde precursors, and reactions of such intermediates with sodium salts from some β-dicarbonyl compounds 2 as well as their possible utility as the Michael acceptors after transformation to the corresponding alkylidene malonates 8 were also demonstrated.     

A new synthesis of 5-hydroxy-6-methyluracil

Dehydration of 5,6-dihydro-5,6-dihydroxy-6-methyl- and 5,6-dihydro-5,6-dihydroxy-1,3,6-trimethyl-uracil in 0.4 M aqueous sulfuric acid gives 5-hydroxy-6-methyl- and 5-hydroxy-1,3,6-trimethyluracil in quantitative yields. Two possible mechanisms have been examined using the mPW1k/6-311+G(2df,2pd)//mPW1k/6-31+G(d,p) method for the transformation of methylated and non-methylated 5,6-dihydro-5,6-dihydroxy-6-methyluracils into the corresponding 5-hydroxy-6-methyluracils. The first is a hydride C5-C6 shift occurring in concert with the loss of a water molecule and formation of the corresponding protonated 5,6-dihydro-5-oxo-6-methyluracils. The second is an acid-catalyzed dehydration reaction to yield 5-hydroxy-6-methyluracils. The calculations demonstrated that the second pathway was energetically most favorable.     

Polyfluoroorganoboron‐Oxygen Compounds. 1 Polyfluorinated Aryl(dihydroxy)boranes and Tri(aryl)boroxins

A general preparative procedure for polyfluorinated aryl(dihydroxy)boranes C₆H_5‐nF_nB(OH)₂ (n = 3 — 5) is described. Polyfluorinated aryl(dihydroxy)boranes are easily dehydrated to the corresponding tri(aryl)boroxins (C₆H_5‐nF_nBO)₃ by thermal or chemical treatment. The property of the acids C₆H_5‐nF_nB(OH)₂ to condensate depends on the number and on the position of the fluorine atoms in the aryl group. Examples of both classes of boron compounds were isolated as pure individuals and characterized by multinuclear NMR spectroscopy.     

加压条件下负载型杂多酸复合催化剂催化甲醇脱水制备二甲醚

合成了负载型杂多酸复合催化剂HSiW-La2O3/ γ-Al2O3,并用吡啶吸附IR光谱、NH32－TPD、N2吸附、UV－DRS、XPS和XRD等手段,对催化剂进行了表征,该催化剂具有中孔结构,表面上具有L酸和B酸,酸分布以弱酸为主,探讨了杂多酸含量,反应压力,反应温度入质量空速对甲脱水制备二甲醚转化率与选择性的影响,实验表明,当HSiW含量为105－16％时,催化剂活性,反应的最佳条件为压力0．75－0．85MPa(gauge),温度280－320℃,质量空速（MHSV）为1．5－2．5h^1。     

Differences in thermal decomposition of Ag(I), Mn(II), Fe(II) and Fe(III) complexes of cyclic dithiocarbamates

The thermal decomposition of pyrrolidinedithiocarbamate (Pyr) and piperidinedithiocarbamate (Pip) complexes of Ag(I), Mn(II), Fe(II) and Fe(III) have been investigated by thermogravimetry and differential scanning calorimetry. The decomposition intermediates and final products were identified from their X-ray diffraction patterns. Changes in their IR spectra were correlated with their thermogravimetric profiles. The hydrated compounds decomposed without loss of water and oxides were detected as the final decomposition products even in nitrogen atmosphere.     

Ac2O/K2CO3/DMSO: an efficient and practical reagent system for the synthesis of nitriles from aldoximes

The transformation of aldoximes to nitriles using acetic anhydride as dehydration agent under mild reaction conditions is reported. The reaction, which proceeds under weak alkaline condition, allows for the conversion of a range of aldoximes including aromatic aldoximes, alphatic aldoximes, and heterocyclic aldoximes in good to excellent yields. This method has also been successfully applied to the synthesis of calcium channel blocker nilvadipine in pilot scale.     

聚(N-甲基丙烯酰-L-β-异丙基天冬酰胺)温敏性驱动力研究

结合紫外-可见光(UV-Vis)、圆二色谱(CD)、动态光散射(DLS)、升温核磁氢谱(1H-NMR)以及溶剂同位素效应研究了聚(N-甲基丙烯酰-L-β-异丙基天冬酰胺),简称为PA48,温敏行为的驱动力因素.浊度实验表明聚合物在酸性水溶液呈现可逆的LCST型温敏性.例如在pH=1时浊点(CP)为39.9℃,降温过程有0.9℃的滞后;CD实验表明吸收波长在温度升高时基本不变;溶剂同位素实验表明PA48在重水中的CP比轻水中低6.0℃;DLS结果表明在溶液温度低于CP时PA48以单分子链存在,而当温度接近CP时形成聚集体,进一步升高温度时聚合物发生去水合化作用从而相分离;变温1H-NMR表明聚合物去水合化顺序为疏水性骨架链,亲水性天冬氨酸侧链.研究表明聚合物温敏行为由疏水相互作用驱动并伴随着去水合化与相分离过程.     

Efficient condensation of carboxylic acids with alcohols catalyzed by fluorous ammonium triflates

The use of fluorous ammonium salts as metal-free catalysts for the direct condensation of equimolar amounts of carboxylic acids and aliphatic alcohols has been investigated. Esterification reactions were thus conveniently carried out under mild fluorous biphasic conditions, in the presence of 1 mol % of fluorous ammonium triflate and without recourse to any additional water removal technique. Good to excellent ester yields were obtained in the case of primary and secondary aliphatic alcohols. The fluorous salt was easily recovered by simple phase separation and reused at least three times without considerable loss of activity.