Concise synthesis of acyl migration-blocked 1,1-difluorinated analogues of lysophosphatidic acid

Lysophosphatidic acid (LPA, 1- or 2-acyl-sn-glycerol 3-phosphate) is an important phospholipid mediator produced by activated platelets and by ovarian cancer cells. Efforts to understand LPA signaling through G-protein-coupled receptors are hampered by the facile acyl migration that results in equilibration to a mixture of the 1- or 2-acyl species under physiological conditions. We describe a new and efficient route to enantiomerically homogeneous lysophospholipid analogues from D-mannitol 1,2:5,6-bis-acetonide to give two 1,1-difluorodeoxy analogues of (2R)-acyl-sn-glycerol 3-phosphate. These compounds are migration-blocked analogues of the labile sn-2 LPA species. The (19)F NMR of diastereotopic fluorines of the difluoromethyl group shows an unexpected solvent dependence.     

The Surface Imprinted Polystyrene Beads Prepared via Emulsion Templates

In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788),the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer,cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed.     

Synthesis and Structures of Titanosiloxane Cage Compounds

Reaction of (triphenylmethyl)silanetriol (1) with cyclopentadienyltitanium trichloride (CpTiCl₃) in the presence of triethylamine as a HCl scavenger gave both compounds of a partial open-cage type {[Ph₃CSiO(OH)]₃(Ph₃CSiO_3/2)(CpTiO_3/2)₄} (2) and cube type (Ph₃CSiO_3/2CpTiO_3/2)₄ (3). The 1:1 reaction of 1 and CpTiCl₃ in toluene solvent at reflux temperature for 3 d afforded compounds 2 (22%) and 3 (36%). When 1 is reacted with a 1.5 fold excess of CpTiCl₃ under the same conditions, compound 3 was obtained in high yield (81%) along with 2 in trace quantities. Compounds 2 and 3 were fully characterized by the analyses of ¹H, ¹³C, ²⁹Si NMR, IR, and FAB MS data. The solid-state structure of 3 was determined by a single crystal X-ray diffraction study. Compound 3 had shown to have catalytic activity for the oxidation of alkenes such as 1-octene, cyclooctene, and norbornene with t-butyl hydrogen peroxide. The effect of solvent was observed in this epoxidation reaction. The order of reactivity were decreased as follows: CHCl₃ > hexane THF.     

新显色剂2-[2-(5-溴-噻唑)偶氮]-5-二甲氨基苯甲酸与铑的显色反应的研究

本文研究了新显色剂5-Br-TAMB与铑(Ⅱ)的显色反应。在pH5.0～7.0的水溶液中,铑(Ⅱ)与5-Br-TAMB形成1:2型稳定的蓝色配合物,其最大吸收波长为674nm,表观摩尔吸光系数为1.1×10~5L·mol~(-1)·cm~(-1),铑(Ⅱ)含量在0～12μg/ml范围内服从比耳定律。采用加入适量EDTA的方法消除了Cu~(2+)、Co~(2+)、Ni~(2+)等干扰离子。建立了一个在二元配合物体系中具有高灵敏度及选择性、稳定、简便地吸光光度测定微量铑(Ⅱ)的新方法。     

The nonlinear shear gradient effect on the shear viscosity of a ternary system near a plait point

We have studied the shear viscosity of a ternary liquid mixture (water-ethanol-chloroform) near a plait point by the capillary method and found an apparently strong levelling-off as we approach the critical point. This levelling-off cannot be explained simply in terms of a strong cusp. It is found that the nonlinear shear gradient effect suggested by Oxtoby can be used to explain this behavior.     

催化褪色光度法测定微量锰（Ⅱ）的研究

本文研究在硫酸介质中，锰（Ⅱ）催化ＥＤＴＡ还原重铬酸银，而使之褪色的新指示反应。确定了催化褪色反应动力学条件，锰（Ⅱ）的浓度在０－０．４μｇ／ｍｌ范围内，工作曲线呈良好的线性关系，检测限为０．０１１μｇ／ｍＬ，该方法用于天然水及污水中锰的测定，获得满意结果。     

Enhanced Kinetic Isotope Effect of the Phosphate-Catalyzed Proton Exchange in N,N'-Dimethylurea

The concerted mechanism of phosphate-catalyzed proton exchange in N,N'-dimethylurea has been studied. Kinetic data were measured using the technigue of NMR line-shape analysis. A significant kinetic isotope effect was observed for the concerted proton transfer in N,N'-dimethylurea and is attributed to the tunnelling effect.     

Isothermal cure characterization of dicyclopentadiene

Conversion (α) and the glass transition temperature (T _g) were investigated during the isothermal cure of endo-dicyclopentadiene (DCPD) with a Grubbs catalyst for different temperatures using differential scanning calorimetry. Conversion vs. In (time) data at an arbitrary reference temperature were superposed by horizontal shift and the shift factors were used to calculate an Arrhenius activation energy. Glass transition temperature vs. conversion data fell on a single curve independent of cure temperature, implying that reaction of the norbornene and cyclopentene ring of DCPD proceeds in a sequential fashion. Implications of the isothermal reaction kinetics for self-healing composites are discussed.     

Correlation hole and physical properties: A model calculation

The correlation hole of Coulson and Nielson and its extension to momentum space by Banyard and Reed is studied by using an exactly solvable model. For this model all relevant quantities pertaining to the correlation hole have been calculated exactly. We use this model to study the relationship between the fit to the correlation hole for an approximate wave function and the closeness of the approximate energies to the exact ones. We show that, although in general the better the fit the closer are the approximate physical quantities to the exact ones, there are exceptions where that is not the case. Also, we present a convenient method for the calculation of the two particle distribution in momentum space and generalize the concept of the correlation hole by defining it in the pseudophase space of position and momentum.     

Sulfonated poly(ether ether ketone)/poly(amide imide) polymer blends for proton conducting membrane

Poly(amide imide) (PAI) was synthesized using 1,2,4-benzenetricarboxylic anhydride (BTBA) and 4,4′-methylenebis(phenyl isocyanate) (MBPI). SPEEK/PAI blend membranes were prepared and investigated by NMR, GPC, FT-IR and AFM. The chemical structures of PAI and SPEEK were characterized by using NMR and FT-IR. The adsorption of the SPEEK/PAI blend membrane of water or methanol solution was also characterized. The significant swelling of the blend membrane in concentrated methanol solution was explained by the solubility parameter. The water diffusion coefficient (D_H2O) was related to the lambda value of the membrane. The SPEEK/PAI blend membrane had a lower proton conductivity and methanol permeability than Nafion. However, the relative selectivity (proton conductivity divided by methanol permeability) of the SPEEK/PAI 70/30 (w/w) blend membrane was 3.46 × 10⁴ S s cm⁻³, which is closed to that of Nafion (3.30 S s cm⁻³).