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201.
A convenient and efficient method for the preparation of unsymmetrical and symmetrical diacetylenic ketones bearing a carboxylate group. 相似文献
202.
The effectiveness of hybrid drying based on convective drying with application of ultrasound and microwave enhancement is the main subject of the studies. The drying kinetics, energy consumption as well as the quality aspect of green pepper is analysed. It was shown that hybrid drying methods shorten significantly the drying time, reduce the energy consumption and affect positively the quality factors. Each of the analysed aspects depend on combination of the convective-ultrasound-microwave drying programs. Besides, based on the drying model elaborated earlier by one of the authors, the effects of ultrasound on convective drying assessed by such phenomena as “heating effect”, “vibration effect” and “synergistic effect” are presented. 相似文献
203.
Jorge Castellanos-Soriano Allen T. Ekubo Mark R. J. Elsegood Nuria Lastra-Calvo Aman Mantry Arturo Martinez-Insua-Rodriguez 《Phosphorus, sulfur, and silicon and the related elements》2017,192(5):570-575
New tetraalkylaminophosphonium chlorides were readily prepared by four-fold condensation of commercially available [P(CH2OH)4]Cl with a range of fifteen aryl based primary amines, in EtOH, at ambient temperature. All compounds have been characterized by FT–IR spectroscopy and elemental analysis. Solution 31P{1H} NMR studies of these chloride salts reveal their instability with respect to various PIII/PV species. The structures of three examples have been determined by single crystal X-ray diffraction and confirm the pseudotetrahedral arrangement around the PV center. Extensive N–H···Cl hydrogen bonding is observed. 相似文献
204.
J. Graham Dawber R. Glynn Skerratt John C. Tebby Albert A. C. Waite 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1261-1268
Abstract Third order rate constants have been determined for the alkaline hydrolysis of four series of alkylphenylphosphonium salts and alkylphenylbenzylphosphonium salts at various temperatures in 50%–70% v/v aqueous tetrahydrofuran and 70% v/v aqueous methanol. Thermodynamic activation parameters have been calculated for the reactions of each substrate and the effects of varying the ratio of alkyl to phenyl groups have been compared, as well as the effects of changes in the nature of the alkyl group. Solvation, as revealed by trends in entropy of activation, plays a largely counter-balancing role with respect to enthalpy and energy of activation. The role of the isokinetic effect is discussed. In aqueous tetrahydrofuran, solvation effects on the hydrolyses of phosphonium salts change as the mole fraction of water changes, and for aqueous methanol the trends in the thermodynamic activation parameters actually reverse. 相似文献
205.
206.
R. Hekmatshoar S. Souri M. Rahimifard 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1605-1609
Protonation of the highly reactive intermediate produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylate 1a–c by methyl-2-hydroxy-3-naphthoate lead to vinyl triphenylphosphonium salts which undergo aromatic electrophilic substitution reaction with phenolate-conjugated base to produce 2a–c. 相似文献
207.
208.
Nobumasa Kamigata 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):667-678
Abstract The synthesis and stereochemistry of tricoordinated optically active selenium and tellurium compounds are described. Telluronium salts, telluronium imides, and seleninic acids were prepared and optically resolved by fractional recrystallization of diastereomeric mixtures or by chromatography using a chiral column of racemic mixtures. Diphenyl dichalcogenides also were optically resolved by chiral crystallization. Their absolute configurations were determined or estimated based on X-ray crystallographic analysis, specific rotations, and circular dichroism spectra. The kinetic studies and the mechanism for the racemization were also studied. 相似文献
209.
210.
Cristofor Simionescu Severian Dumitriu Marcel Popa Cristina Coman Vlad Artenie 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):677-686
Pepsin was immobilized on BIOZAN R (Hercules) with dicyclohexylcarbodiimide as activator. The reaction product obtained has a protein content of 35–110 mg/g of polymer and a proteolytic activity between 20.85–28.75 μmol tyrosine/L·min·g of polymer). The coupling reaction rate is maximum under the following conditions: pepsin/BIOZAN R ratio = 0.52 g/g, DCCI/BIOZAN R ratio = 0.2 g/g, pH = 3.4, reaction time = 4 h. 相似文献