Study of chiral recognition mechanism of O,O-diethyl (p-methylbenzenesulfonamindo)-aryl(alkyl)-methylphosphonates by HPLC with a series of CSPs

Five chiral stationary phases (CSPs) were used to separate the enantiomers of a series of O,O-diethyl (p-methyl-benzenesulfonamindo)- aryl(alkyl)-methylphosphonates. A chiral recognition mechanism was presented to explain the resolution of these compounds. Results show that CSP with strong π-acceptor 3,5-dinitrobenzoyl group and high steric hindrance has the best resolution ability in chiral separation of O,O-diethyi (p-methyl-benzenesulfonamindo)- aryl(alkyl)-methylphosphonates. When a CSP has just a strong π-acceptor 3,5-dinitrobenzoyl or high steric hindrance it does not have good chiral resolution ability. The chiral recognition is more difficult when the CSP has more than one asymmetric center.     

Regioselective Addition of Silyl Enolates to α, β-Unsaturated Aldehyde and its Acetal Catalyzed by MgI_2 Etherate

In our previous letter1, we have reported the unique catalytic reactivity of MgI2 etherate 1 in the chemoselective Mukaiyama-type aldol reactions of aryl or vinyl aldehyde and aldehyde acetals with silyl enolates. Aryl or alkyl a, b-unsaturated aldehydes (and their acetals) are particularly reactive in this catalytic addition reaction due to possibly the effective activation of the electron-rich carbonyl by highly oxyphilic Lewis acidic species, i.e. IMg+, in non-coordinative media (i.e. CH…     

Competitive coupling of amide anion over menthyl propionate anion with aryl radical

A competitive coupling of amide anion over menthyl propionate anion with aryl radicalin photo-S_(RN) 1 mechanism was encountered. The rcaction afforded N-aryl propionic amide in excel-lent yield. In contrast, the expected nucleophilic photo-S_(RN) 1 substitution originating from the carb-anion was observed in the case of t-butyl propionate. According to the proposed mechanisms and MOcorrelation diagrams of the coupling step of nucleophiles with aryl radical, the interesting con-trast is reasonably attributed to the variation in energy gap between π~*c-o and π~*Ar of (ArNu)-Usually, the odd electron of (ArNu)- is weightly populated at π~*c-o, however, the diminished priv-ilege of π~*c-o in menthyl propionate promotes a dominant population of the odd electron at π~*Ar,which leads to the fragmentation of (ArNu)- into the starting carbanion and aryl radical.     

Studies on Phase Behavior of Alkyl Polyglucoside Based on Microemulsions with Modified Fishlike Phase Diagram

The three-phase behavior in the quaternary system of an alkyl (C8/10^- or C12/14^-)polyglucoside / 1-butanol / n-octane / water has been studied at 40℃ with the modified fishlike phase diagram, which is presented by us for the first time. The mass fraction of 1-butanol in the hydrophile-lipophile balanced interfacial layer, A^S, the coordinates of the start point B and the end point E of the phase diagram, and the solubilities of alkyl polyglucoside and 1-butanol in n-octane phase were calculated. The solubilization of the microemulsion was also discussed.     

One-pot synthesis of acenaphtho[1,2-b]furan derivatives

New 9-(alkyl or aryl)acenaphtho[l,2-b]furan-8-(alky or aryl)amine compounds has herein been reported by one-pot reaction of (acenaphthylen-l-yloxy)trimethylsilane,alkyl and aryl aldehydes,and aryl and alky isocyanides in refluxing DMF.     

A facile synthesis of 2-substituted-2,3-dihydro-4(1H)-quinazolinones in 2,2,2-trifluoroethanol

2-Substituted-2,3-dihydro-4(1H)-quinazolinones were obtained in high yields by condensation of anthranilamide with aryl, alkyl or heteroaryl aldehydes or ketones in the refluxing 2,2,2-trifluoroethanol without any catalyst.     

An Efficient Method for α-Alkylation of γ-Butyrolactone

Alkylated lactone is a common structure and segment in many natural products and medicines. The examples of alkylating lactone system at -position, obtained by reaction with alkyl halide such as MeI, in the presence of strong base LDA or it抯 derivatives, are very few1a, 1b. When this method was applied to the aromatic compound, the self-condensation of g-butyrolactone could not be avoided. In our previous work we have reported the hydrogenation of ? -unsaturated carbonyl compounds by cat…     

EXTRACTION CHEMISTRY OF RARE EARTHS BY MONO-ALKYL ISOPROPYLPHOSPHONATES

The influence of chemical structure of ester alkyl group of mono-alkyl isopropylphosphonates on the extraction behaviours of rare earth has been studied. The mono-alkyl isopropylphosphonate bearing β-substituted ester alkyl group shows high K_(ex) value, which is evidently depressed, usually in two orders of magnitude, by introducing a branch chain on the α-position of the ester alkyl group. The steric effect of ligand is usually enhanced due to the characteristic lanthanide contraction.z2The extraction chemistry of rare earths by mono-amylnonyl isopropylphosphonates (MANPP) was studied in detail The thermodynamic function was estimated and the "tetrad effect" between K_(ex) value or △G value and atomic number was observed. In addition, the composition and structure of the coordinated compound was studied. As demonstrated by the experimental data, the extractive separation of Sm and Nd by MANPP in chloride solution was better than that in nitrate system.     

分子内桥连有机钴配合物的合成及热稳定性研究

The intramolecularly bridged alkyl cobaltic complexes are one of important coenzyme B₁₂ model coplexes. In this paper, study on the thermolytic reaction of aqua(3-bromopropyl)cobaloximes in solution revealed that a new intramolecularly bridged alkyl cobaloximes complex was formed and the reaction is influenced by tempertature and solvent. Adding cyclodxtrin has no obvious effect to the rate of the reaction, but various products with different axial bases were obtained. The intramolecularly bridged alkyl cobaloxime complex (bromo(O-trimethylene-dimethy- lglyoxime)(dimethylglyoximate)cobalt(Ⅲ)) was characterized by EA and ESI-MS. Thermogravimetric analysis of this complex found that a carbon radical that from homolysis of the Co-C bond is retained in the proximity of Co^Ⅱ- complex, which is very similar to the behavior of coenzyme B₁₂.     

Studies on Middle-Phase Microemulsions of Green Surfactant n-Dodecyl Polyglucoside C12G1.46

The three-phases behavior in the quaternary stsem of n-dodecyl polyglucoside C12G1.46/1-butanol/cyclohexane/water has been studied at 40℃ in terms of the variables γ and δ.Increasing δ at constant γcauses a phase inversion from an oil-in-water microemulsion in contact with excess oil(winsor I or 2) to a water-in-oil microemulsion in contact with excess water (winsor Ⅱor 2)via a middle-phase microemulsion in contact with excess oil and water(winsor Ⅲor 3).By taking into account the different solubilities of alkyl polyglucoside and 1-butanol in the oil phase,the composition of the hydrophile-lipophile balanced interfacial film in the middle of the three-phase body can be calculated.The effects of different oils and aqueous media on the phase behavior and on the composition of the interfacial film and the efficiency for alkyl polyglucoside to make equal weights of water and oil to a single phase were investigated.It was found that the oil molecules with small molecular volumes can improve the solubilizing efficiency of the surfactant to form single-phase microemulsion.In inorganic salt(NaCl) and acid(HCl) solutions,less 1-butanol is needed than that in alkali(NaOH) solution to form middle-phase microemulsion.     

Synthetic control of cage/network ratio of poly(methylsilsesquioxane)s for storage stability,hardness, and weather resistance of coating films

Poly(methylsilsesquioxane) (PMSQ) was synthesized using a two‐step process consisting of hydrolysis of methyl trimethoxysilane (MTMS) with aluminum chelate catalyst and successive condensation reactions conducted at elevated temperatures. Results of nuclear magnetic resonance and Fourier transform infrared measurements show that all terminal functional groups were Si? OH in PMSQ. Results show further that PMSQ has both a cage structure and a network structure, and a cage/network ratio is represented by a height ratio of ?64.5/?66.6 ppm. PMSQ of different molecular weight but the same Si? OH concentration is obtainable by varying the condensation reaction conditions such as the concentration, temperature, amount of aluminum chelate catalyst, and the solvent solubility parameter. A difference of the cage/network ratio occurs. A different cage/network ratio is dependent on the different reactivities of the intramolecular and intermolecular reactions. The relations of molecular structure of the obtained PMSQ molecular structure were characterized along with functions of storage stability, film hardness, and weather resistance. PMSQ designed with a larger cage/network ratio is necessary to obtain PMSQ with good storage stability and a coating film having good weather resistance. PMSQ designed with a smaller cage/network ratio should be prepared to obtain a coating film with high hardness. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Influence of Thermal Treatments on In-depth Compositional Uniformity of CuIn(S,Se)2 Thin Films

CuIn(S,Se)₂ thin films were prepared by thermal crystallization of co-sputtered Cu-In alloy precursors in S/Se atmosphere. In-depth compositional uniformity is an important prereq-uisite for obtaining device-quality CuIn(S,Se)₂ absorber thin films. In order to figure out the influence of heat treatments on in-depth composition uniformity of CuIn(S,Se)₂ thin films, two kinds of reaction temperature profiles were investigated. One process is "one step profile", referring to formation of CuIn(S,Se)₂ thin films just at elevated temperature (e.g. 500 oC). The other is "two step profile", which allows for slow diffusion of S and Se elements into the alloy precursors at a low temperature before the formation and re-crystallization of CuIn(S,Se)₂ thin films at higher temperature (e.g. first 250 oC then 500 oC). X-ray diffrac-tion studies reveal that there is a discrepancy in the shape of (112) peak. Samples annealed with "one step profile" have splits on (112) peaks, while samples annealed with "two step profile" have relatively symmetrical (112) peaks. Grazing incident X-ray diffraction and en-ergy dispersive spectrum measurements of samples successively etched in bromine methanol show that CuIn(S,Se)₂ thin films have better in-depth composition uniformity after "twostep profile" annealing. The reaction mechanism during the two thermal processing was also investigated by X-ray diffraction and Raman spectra.     

Multifunctional polymethylsilsesquioxane (PMSQ) surfaces prepared by electrospinning at the sol-gel transition: superhydrophobicity, excellent solvent resistance, thermal stability and enhanced sound absorption property

Multifunctional superhydrophobic polymethylsilsesquioxane (PMSQ) surfaces with excellent solvent resistance, thermal stability and enhanced sound absorption property were manufactured by electrospinning. The surfaces with various hierarchical morphologies and hydrophobicity were obtained by electrospinning at the different stages of sol-gel transition of PMSQ prepolymer solution. At the stage with a proper viscosity the superhydrophobic PMSQ surface with a contact angle as high as 151° and a sliding angle as low as 8° was prepared. Due to the excellent thermal stability and solvent resistance properties of the cured PMSQ, the resultant surfaces remain superhydrophobicity after thermal treatment at 300 °C and immersion into many solvents. Additionally, an enhanced acoustical performance and ultra water repellency were obtained simultaneously when the traditional acoustical sponge was decorated with the electrospun PMSQ superhydrophobic surface. The robust superhydrophobic PMSQ surfaces may promise practical applications in many fields.     

E?ect of Thermal Treatment on Structure and Catalytic Activity of Supported Fischer-Tropsch Nano-Cobalt Catalysts for Clean Fuels

"A series of 15%Co/Al2O3 catalysts were prepared by incipient wetness impregnation under various calcination conditions (90-500 oC), and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy experiments (XPS), temperature programmed reduction, and catalytic measurements of hydrogenation of carbon monoxide to long-chained hydrocarbons leading to clean fuels (Fischer-Tropsch synthesis). The results of XPS show the presence of incompletely decomposed cobalt nitrate for catalysts calcined at 90-200 oC, and the presence of Co3O4 for catalysts calcined at 200-500 oC. For the four alumina-supported nano cobalt catalysts with different thermal treatment (200-500 oC), XRD and XPS results illustrated that there were mainly nano Co3O4 crystalite phases of 9-10 nm and the size of cobalt nano-particles did almost not change with the different temperature of thermal treatment. This was different from that of silica-supported cobalt catalysts. The supported cobalt catalyst (CoAp340 sample) calcinated at 340 oC presented a better activity for Fischer Tropsch synthesis to clean fuels, at mild conditions like atmospheric pressure (100 kPa), 1800 mL/g/h and 190 oC; rather than high pressure (2 MPa or more)."     

Can coil-to-globule transition of a single chain be treated as a phase transition?

The effects of the concentration (C) and heating rate on the collapse and association of poly(N-isopropylacrylamide) chains in water have been investigated by use of ultrasensitive differential scanning calorimetry. In the dilute solutions, both the phase transition temperature (Tp) and enthalpy change (DeltaH) increase with the heating rate but decrease with concentration. By extrapolation to zero heating rate and zero concentration, Tp and DeltaH for coil-to-globule transition of a single chain in thermodynamic equilibrium can be obtained. In semidilute solutions, both Tp and DeltaH increase with the heating rate but slightly vary with the concentration. Tp and DeltaH for pure interchain association in equilibrium are obtained by extrapolation to zero heating rate. Our experiments reveal that only intrachain contraction occurs when the concentration is infinitely close to zero. When the concentration is above the overlap concentration (C*), only interchain association exists. In the range 0相似文献   

Transition from transparent aerogels to hierarchically porous monoliths in polymethylsilsesquioxane sol-gel system

A transition from hierarchical pore structures (macro- and meso-pores) to uniform mesopores in monolithic polymethylsilsesquioxane (PMSQ, CH(3)SiO(1.5)) gels has been investigated using a sol-gel system containing surfactant Pluronic F127. The precursor methyltrimethoxysilane (MTMS) undergoes an acid/base two-step reaction, in which hydrolysis and polycondensation proceed in acidic and basic aqueous media, respectively, as a one-pot reaction. Porous morphology is controlled by changing the concentration of F127. Sufficient concentrations of F127 inhibit the occurrence of micrometer-scale phase separation (spinodal decomposition) of hydrophobic PMSQ condensates and lead to well-defined mesoporous transparent aerogels with high specific pore volume as a result of the colloidal network formation in a large amount of solvent. Phase separation regulates well-defined macropores in the micrometer range on decreasing concentrations of F127. In the PMSQ-rich gelling domain formed by phase separation, the PMSQ colloidal network formation forms mesopores, leading to monolithic PMSQ gels with hierarchical macro- and meso-pore structures. Mesopores in these gels do not collapse on evaporative drying owing to the flexible networks and repulsive interactions of methyl groups in PMSQ.     

Ni/Zn/Cr系复合金属氧化物的制备及其光催化还原二氧化碳性能研究

以共沉淀法合成的Ni/Zn/Cr系层状金属氢氧化物(LDHs)经不同温度焙烧获得相应的复合金属氧化物,利用XRD、TG、XPS、TEM、BET和UV-Vis等表征手段对所制备样品的结构、组成、形貌以及吸光特性等进行了分析,并考察了样品在常温常压下光催化还原CO2(g)+H2O(g)的性能.结果表明,以Ni/Zn/Cr-LDHs为前驱体经5 00℃焙烧后可得到晶粒尺寸小、分散均匀度高的多相复合金属氧化物,主晶相为纳米尺度的NiO、Cr2O3、ZnCr2O4和NiCr2O4,在这些金属氧化物的协同作用下,样品表现出较好的光催化还原二氧化碳活性,主产物为CH4和CO.     

聚异丙胺基环硼氮烷裂解制备氮化硼及其抗氧化与介电性能

以异丙胺和三氯环硼氮烷(TCB)为原料,在较温和条件下合成了一种可溶可熔的聚异丙胺基环硼氮烷(PTPiAB),后经高温裂解制得六方氮化硼(h-BN).利用元素分析、TGA、FTIR、XRD和网络分析仪等对先驱体及裂解产物的组成、结构和性能进行了表征.结果表明,PTPiAB的结构中含有B3N3六元环,N-H、C-H和C-N键,其熔点约70 oC.1000 oC时在NH3和Ar中的陶瓷产率分别为45.9 %和52.8 %.NH3中裂解失重主要发生在800 oC以下,1000 oC左右开始结晶,1800 oC时得到BN的(002)晶面间距为0.334 nm,密度为2.03 g·cm-3.该BN表现出了较好的高温抗氧化性能,在空气中900 oC以下增重小于0.3%.此外,室温下测试频率为10 GHz时的介电常数实部和损耗角正切分别为2.48和0.03.     

Fabrication and Characterization of an Organic‐Inorganic Gradient Surface made by Polymethylsilsesquioxane (PMSQ)

Summary: A simple method for the fabrication of a chemical composition gradient from organic to inorganic by the pyrolysis of a polymethylsilsesquioxane (PMSQ) thin film in a gradient temperature field is reported. The resultant chemical gradient surface demonstrates gradual changes in wettability, and slight microstructural changes are observed along the substrate.

FT‐IR spectra of gradient PMSQ surface along the length from the unheated side to the heated side.     

Controllable gelation of methylcellulose by a salt mixture

The effects of a salt mixture consisting of a salt-out salt (NaCl) and a salt-in salt (NaI) on the sol-gel transition of methylcellulose (MC) in aqueous solution have been studied by means of micro differential scanning calorimetry and rheometry. The salt mixture was found to have a combined effect from the salt-out and salt-in salts in the mixture, and the salt effect was dependent on the water hydration abilities of the component ions and ion concentration. At a fixed total salt concentration, the sol-gel transition temperature nicely followed a rule of mixing: Tp = m1Tp1 + m2Tp2 where Tp, Tp1, and Tp2 are the gelation peak temperatures for the MC solutions with a salt mixture, NaCl, and NaI, respectively, and mi is the molar fraction of the salt component i in the salt mixture. The linear rule of mixing proved that the effects of NaCl and NaI on the sol-gel transition of MC are completely independent. In addition, the presence of a single salt or a salt mixture in a MC solution does not change the essential mechanism of MC gelation. Therefore, the sol-gel transition of MC can be simply controlled by a salt mixture consisting of a salt-out salt and a salt-in salt. The rheological results supported the micro thermal results excellently. But the gel strength of MC containing salts was influenced by both salt type and salt concentration.