Search results for "supporting"
showing 10 items of 82 documents
The Pd3(dppm)3(CO)2+ Cluster: An Efficient Electrochemically Assisted Lewis Acid Catalyst for the Fluorination and Alcoholysis of Acyl Chlorides.
2002
The dicationic palladium cluster Pd3(dppm)3(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCO…
Electrochemical incineration of oxalic acid at boron doped diamond anodes: Role of operative parameters
2008
The electrochemical incineration of oxalic acid (OA) at boron doped diamond (BDD) anodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the performances of the process. Polarization curves and chronoamperometric measurements indicate the probable occurrence of a direct electrochemical oxidation of OA at the surface of the BDD anode at low pH and of a hydroxyl radical-mediated reaction at high pH. When incineration electrolyses are performed at low pH with potentiostatic alimentation, a dramatic influence of the potential is observed. In amperostatic incineration, high CE are obtained when most part of the process was unde…
Adaptative Network Topology for Data Centers
2016
Data centers have an important role in supporting cloud computing services (such as email, social networking, web search, etc.) enterprise computing needs, and infrastructure-based services. Data center networking is a research topic that aims at improving the overall performances of the data centers. It is a topic of high interest and importance for both academia and industry. Several architectures such as FatTree, FiConn, DCel, BCube, and SprintNet have been proposed. However, these topologies try to improve the scalability without any concerns about energy that data centers use and the network infrastructure cost, which are critical parameters that impact the performances of data centers…
Electrochemical Synthesis of 5-Aryl-phenanthridin-6-one by Dehydrogenative N,C Bond Formation.
2018
Currently, the general synthesis of 5-aryl-phenanthridin-6-ones relies on the involvement of metal catalysis. Despite the urgent demand for green alternatives, avoiding synthetic routes that require transition metals for key roles is still challenging. Electrochemical efforts employing a constant potential protocol in divided cells revealed a possible alternative to the catalytic approach. A constant current protocol, undivided cells, and a remarkably low supporting electrolyte concentration enable a novel access to N-aryl-phenanthridin-6-ones by anodic N,C bond formation using directly generated amidyl radicals. Easy accessible starting materials, a broad scope of applicable functional gro…
Electrochemical synthesis of carbazoles by dehydrogenative coupling reaction
2020
Abstract A constant current protocol, employing undivided cells, a remarkably low supporting electrolyte concentration, inexpensive electrode materials, and a straightforward precursor synthesis enabling a novel access to N‐protected carbazoles by anodic N,C bond formation using directly generated amidyl radicals is reported. Scalability of the reaction is demonstrated and an easy deblocking of the benzoyl protecting group is presented.
Electrochemical nitration with nitrite
2021
Aromatic nitration has tremendous importance in organic chemistry as nitroaromatic compounds serve as versatile building blocks. This study represents the electrochemical aromatic nitration with NBu4 NO2 , which serves a dual role as supporting electrolyte and as a safe, readily available, and easy-to-handle nitro source. Stoichiometric amounts of 1,1,1-3,3,3-hexafluoroisopropan-2-ol (HFIP) in MeCN significantly increase the yield by solvent control. The reaction mechanism is based on electrochemical oxidation of nitrite to NO2 , which initiates the nitration reaction in a divided electrolysis cell with inexpensive graphite electrodes. Overall, the reaction is demonstrated for 20 examples w…
Electrochemical processes in macro and microfluidic cells for the abatement of chloroacetic acid from water
2014
Abstract The remediation of solutions contaminated with monochloroacetic acid (CAA), which is one of the most resistant haloacetic acids (HAAs) to chemical degradation, dramatically depends on the adopted electrochemical approach: (i) CAA is only poorly oxidized either by homogeneous hydroxyl radical in electro-Fenton (EF), electrogenerated active chlorine or electro-oxidation on Pt anode; (ii) it is moderately abated by direct reduction on silver or compact graphite cathodes (from 30% in macro cells to 60% in the microfluidic devices); (iii) it is quantitatively removed by direct electro-oxidation on a boron-doped diamond (BDD) anode. The use of a microreactor enables operation in the abse…
Ceramic foam supported active materials for boron remediation in water
2015
Due to the narrowrange between boron necessities and toxicity in the environment, there is a high interest in the design of effective boron remediation procedures. We have previously reported a promising boron adsorptionmaterial based on the affinity of boron aqueous species for cis-diol groups that were anchored on differentmesoporous silica matrices.However, the small particle size of these systemsmakes themdifficult to be applied on real remediation situations. In this context we report herein a novel systemfor boron adsorption fromaqueous solutions inwhich the high boron affinity for functionalized mesoporousmaterials is combined with themechanical properties of ceramic foams as macrosc…
Studien zum Vorgang der Wasserstoffübertragung, 49: Zur Frage der Auslösung einer optischen Induktion durch Anwendung optisch aktiver Ephedrinderivat…
1978
Die quartaren Ephedriniumsalze 1–5 sowie die bekannten Kronenether 6 und 7 werden als Leitsalze bei der Elektroreduktion von Acetophenon eingesetzt. Hierbei wird das Produktverhaltnis: sekundarer Alkohol (A) zum Diol (B) sowie die optische Induktion von A wesentlich durch das Leitsalz beeinflust. Es wird hieraus der Schlus gezogen, das weniger die Elektrosorption der Leitsalze an die Quecksilberoberflache als vielmehr feldbedingte Orientierungs- und Assoziations-phanomene zwischen optisch aktivem Leitsalz und prochiralem Substrat im diffusen Bereich der elektrochemischen Doppelschicht wirksam sind. Studies on the Occurrence of Hydrogen Transfer, 49: On the Optical Induction Produced in the …
Weak alkali and alkaline earth metal complexes of low molecular weight ligands in aqueous solution
2008
This work is aimed at reviewing the chemical literature dealing with thermodynamic aspects of the weak complex formation (species with log K values less than about 3) between alkali and alkaline earth metal ions with low molecular weight inorganic and organic ligands in aqueous solution. The following ligands (up to hexavalent anions) were examined in detail: (i) hydroxide, chloride, sulfate, carbonate and phosphate as inorganic, and (ii) carboxylates, amines, amino acids, complexones and nucleotides as organic ligands. The paper also identifies the main reasons responsible for the dispersion of the stability data on ion pairs in the literature. When possible, the trend of stability for the…