Search results for "Homogeneous"
showing 10 items of 718 documents
Sunlight-induced reactions of some heterocyclic bases with ethers in the presence of TiO2
2005
The reactions between various heterocyclic bases and ethers induced by sunlight are reported. In several cases the photoreaction occurred with higher yields in liquid–solid heterogeneous system in the presence of polycrystalline TiO2 than in homogeneous system. The derivatives obtained with trioxane may give an easy entry to heterocyclic aldehydes.
Synthetic Application of Homogeneous Charge Transfer Catalysis in the Electrocarboxylation of Benzyl Halides
1998
The results of an investigation on the performances of some outer sphere electron transfer homogeneous catalysts in the electrocarboxylation of 1-(p-isobutyl-phenyl)-1-chloroethane to 2-(p-isobutyl-phenyl)-propionic acid (Ibuprofen), using as catalysts the esters of benzoic and o-, m-, and p-phtalic acids, are reported. The performances of the catalysts are evaluated on the basis of the following parameters: faradic yields of the carboxylation and decomposition of the catalyst. The performances of dimethylisophtalate have been examined in greater detail. The rate of decomposition of the catalyst is related to the molar ratio [halide]/[catalyst].
Ionic Liquids in Biphasic Ethylene Polymerisation
2011
Over the past several years there has been a considerable increase in the interest of ionic liquids as versatile reaction media for a wide variety of synthetic processes. The popularity of ionic liquids has been related primarily to their unique physical and chemical properties, which can be tailored by the judicious selection of cations and anions. These properties make it possible to use ionic liquids as solvents for many organic, inorganic, and organometallic compounds, including catalysts and co-catalysts, for various types of reactions. In particular, the polar but weakly coordinating character of ionic liquids enables them to be applied as mediums in catalysis, to immobilize various k…
PHOSPHORORGANISCHE VERBINDUNGEN 105.1Synthese chiraler und achiraler ditertiärer 1-Phosphino-2-Aminoethan-Derivate ([dbnd]P [sbnd]CH2[sbnd]CHR[sbnd]N…
1983
Abstract Primary amines with an optical active ligand add to vinyl- and propenylphosphonium salts according the reaction schemes (5) and (6), forming compounds of the type E and F. F contains a new asymmetric center in the bridge giving rise to the formation of a mixture of diastereomers, which can be resolved. Phosphonium salts of type E and F with a benzyl group on the phosphonium center are cleaved reductively by alkali amalgams (Li/Hg; Na/Hg; K/Hg) forming tertiary phosphines with an aminogroup in the β-position. The reductive cleavage with alkali amalgams is superior to the cathodic cleavage. Application: The synthesis of Ni(O)- and Pd(O)-complexes of type J fails. Bis-phosphine comple…
Organolanthanides as single component homogeneous catalysts for isoprenehex—1-ene co-polymerisation
1999
Abstract Bisallylansalanthanide complexes act as single component catalysts of diene polymerisation; from an equimolar mixture of isoprene and hex-1-ene, a co-polymer hex-1-ene/isoprene = 1:10 is obtained, this copolymer is essentially formed of 1,4- trans polyisoprene blocks separated by only one inserted hexyl group.
Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes
2012
Electrochemical monitoring of the oxidative coupling of alkynes in the homogeneous phase through catalytic cycles involving triphenylphosphine gold complexes and selectfluor as oxidant reveals that at least two gold species in +3 and +1 oxidation states are implicated. Electrochemically driven homocoupling of terminal alkynes using molecular oxygen as the oxidant can be performed using such catalysts. Keywords: Gold catalysis, Oxidative coupling of alkynes, Oxygen, Voltammetry
Networked Analysis of a Teaching Unit for Primary School Symmetries in the Form of an E-Book
2021
In mathematics education, technology offers many opportunities to enrich curricular contents. Plane symmetries is a topic often skipped by primary teachers. However, it is important and may be worked in attractive ways in dynamic geometry software environments. In any regular classroom there are students with different levels of mathematical attainment, some needing easy tasks while others, particularly mathematically-gifted students, need challenging problems. We present a teaching unit for plane symmetries, adequate for upper primary school grades, implemented in a fully interactive electronic book, with most activities solved in GeoGebra apps. The book allows student to choose which itin…
Urban Growth and Real Estate Income. A Comparison of Analytical Models
2016
I processi di crescita urbana sono notoriamente complessi dipendendo da un’ampia varietà di fattori demografici, socio-culturali ed economici. L’analisi è ancora più complessa nelle aree metropolitane che sono il risultato di antichi processi di agglomerazione in una fase d’intenso accrescimento dell’insediamento e, più recentemente, della formazione di policentrismo urbano. L’investigazione richiede l’acquisizione, l’analisi e l’elaborazione d’idonee informazioni a livello delle unità territoriali omogenee, basandosi su modelli consolidati o su nuovi protocolli da verificare. Il presente contributo analizza la crescita urbana secondo un approccio di piccola scala, individuando i distretti …
Semi-terminal continua in homogeneous spaces
2016
A semi-terminal continuum Y in a space X is defined by the condition that no two disjoint subcontinua of X intersect both Y and X-Y. Though numerous obvious examples of such continua can be found in arcs, trees and tree-like continua, these examples are related to the non-homogeneity of the space, and having semi-terminal continua in a homogeneous continuum is counter-intuitive. Recently, a large collection of homogeneous spaces with semi-terminal, non-terminal subcontinua has been found. This paper is devoted to studying these spaces and the general structure of homogeneous continua related to the presence of semi-terminal subcontinua.
Inter- and Intraobserver Variation in the Assessment of Preoperative Colostograms in Male Anorectal Malformations: An ARM-Net Consortium Survey
2020
Aim:Male patients with anorectal malformations (ARM) are classified according to presence and level of the recto-urinary fistula. This is traditionally established by a preoperative high-pressure distal colostogram that may be variably interpreted by different surgeons. The aim of this study was to evaluate the inter- and intraobserver variation in the assessment by pediatric surgeons of preoperative colostograms with respect to the level of the recto-urinary fistula. Materials and Methods:Sixteen pediatric surgeons from 14 European centers belonging to the ARM-Net Consortium twice scored 130 images of distal colostograms taken in sagittal projection at a median age of 66 days of life (rang…