ETUDE STRUCTURALE DE QUELQUES SPIROPHOSPHORANES A LIAISON P–C EXOCYCLIQUE

Abstract

The PMR spectra of some spirophosphorans containing the P–C bond are analysed. The results allow us to determine the stereochemistry of these compounds (conformation, stereoisomerism).

Le spectre de RMP de quelques spirophosphoranes à liaison P–C est analysé. Les résultats sont utilisés pour préciser la stéréochimie de ces composés (conformation, stéréoisomérie).     

MAGNESIUM HYDROGEN SULFATE POWDER CATALYZED STEREOSELECTIVE CONVERSION OF DIALKYL 2-(IMIDO-N -YL)-3-(TRIPHENYLPHOSPHORANYLIDENE)- BUTANEDIOATES TO ELECTRON-POOR (Z)-N -VINYLIMIDES IN SOLVENT-FREE CONDITIONS

Magnesium hydrogen sulfate powder was found to catalyze stereoselective conversion of dialkyl 2-(imido-N-yl)-3-(triphenylphosphorany-lidene)butanedioates to electron-poor (Z)-N-vinylimides in solvent-free conditions at 95°C 1 h in high conversions. Microwave also was found to catalyze the same reactions in the presence of magnesium hydrogen sulfate powder in solvent-free conditions in 3 min.     

Al(HSO4)3 and Al2O3-SO3H as Efficient Catalysts for Modified Preparation of 3,4-Dihydropyrimidin-2 (1H)-ones/thiones

An environmentally friendly procedure for the preparation of dihydropyrimidinone derivatives or their sulfur analogues under thermal solvent-free conditions in the presence of aluminium hydrogen sulfate [Al(HSO₄)₃] and alumina sulfuric acid (Al₂O₃-SO₃H) as heterogeneous catalysts was developed.     

Solid State S-Methylation of Thiols and O-Methylation of Phenols and Naphthols with Dimethyl Sulfate Under Microwave Irradiation

Abstract

Mild and efficient S-methylation of thiols and o-methylation of phenols and naphthols occurs with dimethyl sulfate (DMS) supported on basic alumina under microwave irradiation in solventless system.     

Li-defect interactions in electron-irradiated n-type silicon by EPR measurements

Single crystal silicon, both with and without oxygen, has been diffused with lithium to concentrations ～10¹⁷/cm², irradiated with 1 to 1.5 MeV electrons, and the ensuing defects studies by EPR measurements. The presence of oxygen strongly affects the properties of these defects. Measurements have indicated the presence of two new defects which involve Li-one in O-containing material and one in O-free material. The defects are observed in their electron-filled state, and indicate a net electron spinof ½. The defect spectra disappear (with time) at room temperature, and can be explained by the formation of other Li-involved defects which lie deeper in the energy bandgap and are not visible by EPR. Electron irradiation at 40 °K followed by annealing at higher temperatures show that both EPR defects described above begin to form at about 200 °K and begin to decrease at about 275 °K-just as does the 250 °K reverse annealing observed generally for n-type Si. Based on these data, and the work of others, it is suggested that both defects form as a result of the motion of Si interstitials which produce a (Li-O-interstitial) complex in O-containing Si, and a (Li-interstitial) complex in O-free Si.     

Regeneration of Carbonyl Compounds from Oximes and Hydrazones Using Peroxymonosulfate on Silica gel under Solvent-free Conditions

In an environmentally benign solvent-free system, oximes and hydrazones are rapidly transformed into parent carbonyl compounds using peroxymonosulfate on silica gel under microwave irradiation in good to excellent yields.     

Radiation damage by soft β-particles self-irradiation of β-tritiated polystyrene

The effect of self-irradiation of β-tritiated polystyrene under high vacuum at 25°C was studied, and simultaneous random chain scission and cross-linking were observed. Analyses of the gaseous products and the colored polymer residue showed that hydrogen was the only volatile product, while spectroscopic measurements indicated that the coloration was associated with the presence of main-chain double bonds.

G values for hydrogen formation GH₂, cross-linking, G _XL and chain scission, G _CS were obtained as follows: GH₂=0.031; G _CS=0.044; G _XL=0.061. Possible mechanisms of radiation damage are discussed.     

One-pot,direct synthesis of acyl azides from carboxylic acids using Ph2PCl/I2/NaN3 reagent system

A mild,efficient and simple method for the preparation of acyl azides from carboxylic acids using chlorodiphenylphosphine in the presence of molecular iodine and sodium azide is described.     

添加CaSO4·2H2O为晶种制备磷石膏半水硫酸钙晶须

以固体废弃物磷石膏为原料,在传统常压醇水热法的基础上添加CaSO₄·2H₂O为晶种制备半水硫酸钙晶须。采用单因素试验法探究了晶种含量、丙三醇含量和磷石膏质量分数对晶须结构和形貌的影响,确定晶须的最佳制备工艺条件。采用SEM和XRD对样品进行表征分析,实验结果表明:添加CaSO₄·2H₂O晶种制备晶须的长径比(49.29)比只添加丙三醇的样品的长径比(30.99)提高了近60%;当丙三醇与水的体积比(V)为1、晶种含量为1%、磷石膏质量分数为5%时制备的晶须的平均直径为0.65 μm,长径比达到了62.15,晶须的尺寸均匀。这说明添加1%CaSO₄·2H₂O晶种、V为1的丙三醇和质量分数为5%的磷石膏在常压下能制备出高长径比和尺寸均匀的半水硫酸钙晶须。     

Characterization of sugar juice heat exchanger tube deposit

Fouling of heat exchanger surfaces during sugar manufacture reduces productivity and increases energy demand. This study characterizes a deposit (including its internal structure) formed in a sugar factory's evaporator unit using a variety of X‐ray diffraction and scanning electron microscopy techniques (including X‐ray powder diffraction, X‐ray fluorescence, elemental mapping with energy dispersive spectroscopy and backscattered electron imaging). Calcium sulfate dihydrate, calcium oxalate mono‐ and dihydrate, hydroxyapatite, amorphous silica and organic matter are present in the deposit. The composition of the deposit (which contains three layers) varies along the height of the tube. There are noticeable differences in the composition and porosity among the layers in the deposit. A porous structure consisting of a mixture of amorphous silica, calcium oxalate dihydrate and organic matter is attached to the surface of the deposit in contact with sugar juice, while a denser morphology of amorphous silica and hydroxyapatite is attached to the tube wall. Elemental mapping identifies an association between Si, Al, Mg, Fe and O, suggesting the presence of a silicate compound as a minor component in the deposit. An attempt is made to rationalize the formation of the observed phases. Copyright © 2010 John Wiley & Sons, Ltd.