Search results for "Amination"
showing 10 items of 1702 documents
NHC-Stabilized Gold(I) Complexes: Suitable Catalysts for 6-exo-dig Heterocyclization of 1-(o-Ethynylaryl)ureas
2010
3-Substituted 1-(o-ethynylaryl)ureas 1 selectively undergo either 6-exo-dig or 5-endo-dig cyclization (to give 4-methylene-3,4-quinazolin-2-ones 2 or indoles 3, respectively) depending on the choice of the metal, ligand, and reaction conditions. The best results (up to 96% yield) in the preparation of the hydroamination products 2 are achieved with the highly bulky NHC-stabilized cationic gold(I) complex [Au(IPr)](+). Conversely, ureas bearing an internal alkyne lead to the 5-endo-dig cyclization mode regardless of the gold(I) complex employed. Whereas the nature of the substituent at N-3 does not have any influence on the regiochemistry observed, it does, in some cases, affect the efficien…
Chemical recycling of polyenaminones by transamination reaction via amino–enaminone polymerisation/depolymerisation
2019
Abstract Novel oligo- and polyenaminones with Mw ∼ 3000 Da were prepared in excellent yields by amino–enaminone ‘click’ polymerisation of 1,3- and 1,4-bis[3-(dimethylamino)acryloyl]arenes with 1,3- and 1,4-phenylenediamine. The obtained oligomers and polymers were depolymerised quantitatively to the starting bis-enaminones and diamines by treatment with excess dimethylamine in ethanol at 50 °C. This simple polymerisation/depolymerisation method allows for a closed-loop recycling of polyenaminone-based materials. UV light absorbance at wavelengths below 470 nm indicates promising optical properties of these polymers.
Recent Applications of Carbonaceous Nanosorbents in Solid Phase Extraction for the Determination of Pesticides in Food Samples
2018
This article covers recent trends of carbonaceous nanomaterial supported solid phase extraction for the liquid and gas chromatography analysis of pesticides in food samples. Several advanced carbonaceous nanosorbents have been reported over the previous decade for pesticide extraction, such as graphene derivatives modified by combination with silica, amines, polymers, and/or magnetic nanoparticles. The advances in this field have opened possibilities for using neat or modified carbon nanotubes or graphene-type sorbents for the pre-concentration of polar or nonpolar pesticides by solid phase extraction (SPE) or micro-SPE methods or to apply such nanomaterials for the removal of matrix compon…
Accidental Contamination of Substrates and Polymer Films by Organic Quantum Emitters.
2019
[Image: see text] We report the observation of ubiquitous contamination of dielectric substrates and poly(methyl methacrylate) matrices by organic molecules with optical transitions in the visible spectral range. Contamination sites of individual solvent-related fluorophores in thin films of poly(methyl methacrylate) constitute fluorescence hotspots with quantum emission statistics and quantum yields approaching 30% at cryogenic temperatures. Our findings not only resolve prevalent puzzles in the assignment of spectral features to various nanoemitters on bare dielectric substrates or in polymer matrices but also identify the means for the simple and cost-efficient realization of single-phot…
Contamination from polycyclic aromatic hydrocarbons (PAHs) in the soil of a botanic garden localized next to a former manufacturing gas plant in Pale…
2010
The Botanical Garden lies within the city of Palermo, a few meters away from one of the largest unused Manufacturing Gas Plant in Sicily. The total concentrations of PAHs (23 compounds) in the soil of Botanical Garden ranged from 947 to 18,072 microg/kg. The wide range of PAH concentrations (RSD=84%) found in the soil samples indicates heterogeneous levels of contamination in the area and this can be explained by considering the different tree distributions which prevents the homogeneous deposition of pollutants on the soil. Soils collected in the Botanical Garden generally showed the highest PAH concentrations, being almost 2-3 times higher than the concentration samples obtained in the ur…
Heavy metals in sewage sludges contribute to their adverse effects on the arbuscular mycorrhizal fungusGlomus mosseae
2003
Applying sewage sludges to agricultural land is a widespread practice because of the sludges’ agronomic value as a source of plant nutrients and organic matter. Nevertheless, sludges often contain micropollutants that can constitute a menace for health and the environment. Arbuscular mycorrhizal fungi are sensitive to sewage sludges that have been spiked, or not, with metallic trace elements (MTE). Here we have investigated if MTE in sewage sludges could be responsible for effects on mycorrhizal development betweenGlomus mosseae andMedicago truncatula. The impact of a dehydrated or composted urban sewage sludge spiked or not with MTE, was tested on spore germination and root colonization by…
Remediation of Soil Contamination with Heavy Metals by Using Zeolite and Humic Acid Additives
2012
- Soil remediation at contaminated sites very often needs customized approach, because of the different content of pollutants. Various technologies from simple soil excavation and transporting to hazardous waste landfills to different kinds of remediation by vitrification and the use of additives can be used for the treatment of soil. A series of remediation experiments using zeolites and humic acids were applied to soil contaminated with copper. Remediation can be performed with easily available additive materials of natural origin found near the place of application, in order to diminish the leaching of contaminants. Soils contaminated and spiked with copper were mixed with additives, and…
Decomposer animal communities in forest soil along heavy metal pollution gradient
1996
Responses of soil decomposer animals to heavy metal contamination and to concomitant changes in organic matter quality and quantity and in soil microbial biomasses have been studied along a pollution gradient from a Cu-Ni smelter. Samples have been taken separately for nematodes, enchytraeids and microarthropods 0.5, 2 and 8 km from the smelter. Special attention has been paid to the changes in the collembolan fauna. The sampling sites have been located in homogeneous Scots pine ( Pinus sylvestris) forests with podsolic soil profiles. In addition, an experiment has been carried out in which intact soil cores have been transferred in mesh baskets between the sites 2 and 8 km from the smelter…
Alkene epoxidations catalysed by Mo(VI) supported on Merrifield's polymer
1999
High conversion and epoxide selectivity from alkenes is achieved with tert-butyl hydroperoxide and a polystyrene-grafted Mo(VI) catalyst, with no noticeable leaching of Mo from the support.
Polycyclic Aromatic Hydrocarbons in Sediments of Marine Coastal Lagoons in Messina, Italy: Extraction and GC/MS Analysis, Distribution and Sources
2004
The content of 21 polycyclic aromatic hydrocarbons (PAHs) has been determined in 16 samples of sediments collected from Ganzirri and Faro marine coastal lagoons in Messina (Italy). Analysis was performed by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. The total concentration of polycyclic aromatic hydrocarbons (PAHs) ranged from 74 to 5755 ...g/Kg of dry matrix. The resulting distributions and molecular ratios of specific compounds have been discussed in terms of sampling location and origin of organic matter. The results obtained show that levels of contamination are not homogeneous throughout the stations, while the relative distributions of PAH are…