Process intensification using cavitation: optimization of oxidation conditions for synthesis of sulfone

Cavitation can be effectively used for intensification of chemical reactions due to the production of free radicals and conditions of high temperatures and pressures locally. In the present work, use of cavitation for the intensification of the synthesis of sulfone has been explored. The oxidation of thioether or sulfide to synthesize corresponding sulfone with 30% H₂O₂ as an oxidant was studied under acoustic cavitation and the results have been compared with the conventional approach based on the use of mechanical agitation. The aim has been also to optimize the different operating conditions viz. molar ratio of reactants to the oxidizing agent, type of the catalyst as well as its concentration, type of the solvent and the reactant concentration, so as to maximize the degree of intensification. It was observed that under the optimized conditions of sonication, the yield of sulfone was about five to six times higher as compared to the conventional approach of using mechanical agitation only.     

Simulation of the spatial distribution of the acoustic pressure in sonochemical reactors with numerical methods: A review

Numerical methods for the calculation of the acoustic field inside sonoreactors have rapidly emerged in the last 15 years. This paper summarizes some of the most important works on this topic presented in the past, along with the diverse numerical works that have been published since then, reviewing the state of the art from a qualitative point of view. In this sense, we illustrate and discuss some of the models recently developed by the scientific community to deal with some of the complex events that take place in a sonochemical reactor such as the vibration of the reactor walls and the nonlinear phenomena inherent to the presence of ultrasonic cavitation. In addition, we point out some of the upcoming challenges that must be addressed in order to develop a reliable tool for the proper designing of efficient sonoreactors and the scale-up of sonochemical processes.     

镉掺杂氧化锌纳米晶禁带宽度的尺寸效应和掺杂效应研究

Cadmium-doped zinc oxide nanocrystals in the quantum confinement region have been firstly synthesized by a fast and facile sonochemical method.The alloyed structure of the nanocrystals is confirmed by X-ray diffraction,transmission electron microscopy,and infrared analysis.With the increase of cadmium to zinc molar ratio from 0 to 2.0,the crystallite sizes of the samples decrease from 5.1 nm to 2.6 nm,and the band gaps of the samples show a red shift then a blue shift,and a red shift again.The variations of band gaps of the samples can be interpreted by the crystallite size and the composition.It is found that both the non-thermal equilibrium environment established in the sonochemical reaction and the coordination ability of triethylene glycol solvent play crucial roles in the current preparation.     

超声空化与超声医学

随着超声技术应用广泛而迅速的发展,整整一个世纪来,超声空化成了经久不衰的研究课题,特别近１０年来,超声空化成了多种学科的基础研究热点。本扼要地介绍了起声空化的最新研究进展,以及超声空化与超声医学发展的密切关系。     

Practical selective monohydrolysis of bulky symmetric diesters: Comparing with sonochemistry

The conditions of the practical selective monohydrolysis of symmetric diesters we previously reported have been modified and applied to selective monohydrolysis of bulky symmetric diesters. While ultrasound is generally considered effective for two-phase reactions, its effect actually turned out to be rather marginal. Instead, use of a larger proportion of a polar aprotic co-solvent, DMSO, and aqueous KOH helped enhance the reaction rates and improve the yields of the half-esters. The reactions are simple, mild and practical without special devices.     

The effect of high intensity ultrasound on the synthesis of some polyurethanes

High intensity ultrasound has been applied to the preparation of polyurethanes from a number of diisocyanates and diols. In all cases, the sonochemical reactions proceeded faster in the early stages and led to higher molecular weight polymers. The effect of changing the ultrasound intensity is discussed and some speculation as to the mechanism of the reaction enhancement is given.     

Ionic Liquid in Synthesis: A Phase Transfer Reagent and a Redox Mediating Medium

Ionic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to depolymerize MX₂ (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2′‐bipyridine (= bpy) to give the (bpy)MX₂ product. Supersonic irradiation of equiv‐molar bpy, PdX₂, and IL in CHCl₃ produced almost quantitative precipitate of (bpy)PdX₂ in a short time at ambient temperature, where IL is either [BEIm]Br or [BMIm]Br. That is, ILs and sono‐techniques assisted greatly on the synthesis of (bpy)PdX₂. For preparation of (bpy)PtX₂, nonetheless, free bpy always remained in mixture even after a long time of supersonic treatment. The system of equiv‐molar bpy, PtBr₂, and IL in CHCl₃, produced yellow (bpy)PtBr₂ and orange (bpy)PtBr₄, both being characterized with ¹H NMR and ¹⁹⁵Pt NMR in d₆‐Me₂SO as well as with single crystal X‐ray diffraction. Overall for PtX₂ reactions with halide anions in highly polar environments attributable to ILs, the redox pathway becomes important in that Pt(II) transforms to Pt(IV) to yield (bpy)PtBr₂ and (bpy)PtBr₄.     

Synthetic approaches to 5,7- and 5,8-dimethoxyquinoline. Sonochemical dehalogenation of substituted 2,4-dichloroquinolines. Use of the 2D COLOC spectrum for the NMR assignment of 5,8-dimethoxyquinoline

Summary Sonochemical dehalogenation of 2,4-dichloroquinoline is very facile. However, with 5,7-dimethoxy-2,4-dichloroquinoline the reaction proceeds stepwise to provide the title dimethoxyquinolines which cannot be prepared via theSkraup reaction. The¹³C NMR chemical shift assignments for 5,8-dimethoxyquinoline are presented. These were made by utilising the coupling connectivities from the bridgehead carbons in the 2D COLOC spectrum.

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Synthese von 5,7- und 5,8-Dimethoxychinolin. Sonochemische Dehalogenierung von substituierten 2,4-Dichlorochinolinen. NMR-Spektroskopische Zuordnung von 5,8-Dimethoxychinolin mittels eines COLOC-Experiments

Zusammenfassung 2,4-Dichlorchinoline können sonochemisch leicht dehalogeniert werden. Mit 5,7-Dimethoxy-2,4-dichlorchinolin verläuft die Reaktion in mehreren Schritten zu den Titelverbindungen, die mittelsSkraup-Reaktion nicht hergestellt werden können. Das¹³C-NMR-Spektrum von 5,8-Dimethoxychinolin wurde, ausgehend von den Brückenkopfkohlenstoffatomen, mit Hilfe eines COLOC-Experiments zugeordnet.

     

Sonochemical synthesis of silver, copper and lead selenides

Ag₂Se, CuSe and PbSe were prepared by irradiating the mixtures of AgNO₃, CuI or PbCl₂ with selenium in ethylenediamine (en) with ultrasound at 18 kHz, using a commercial ultrasonic cleaner, respectively. X-ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) images show that the products are orthorhombic Ag₂Se, hexagonal CuSe and cubic PbSe, respectively, and all are well crystallized in nanometers.     

Ultrasound Promoted 1, 3-Dipolar Cycloaddition Reactions of Nitrile Oxides with α, β-Unsaturated Acetals

The 1,3-dipolar cycloaddition reactions of nitrile oxides and α,β-unsaturated 1,3-dioxolanes were effectively accelerated by ultrasound irradiation to give the A²-isoxazolines with yields and regioselectivities surpassing those of the corresponding thermal reactions.