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Aryl C (aryl + c)
Selected AbstractsChemInform Abstract: Cu(II)-Mediated Methylthiolation of Aryl C,H Bonds with DMSO.CHEMINFORM, Issue 34 2010Lingling Chu Abstract A new and convenient method for the methylthiolation and ethylthiolation of arenes is reported. [source] Palladium-Catalyzed Alkylation of Aryl C,H Bonds with sp3 Organotin Reagents Using Benzoquinone as a Crucial Promoter.CHEMINFORM, Issue 19 2006Xiao Chen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A comparison of two methods for the isolation of free and occluded particulate organic matterJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2005Angelika Kölbl Abstract Various methods exist for the isolation of particulate organic matter (POM), one of the soil-organic-matter (SOM) fractions reacting most sensitive on land-use or soil-management changes. A combination of density separation and ultrasonic treatment allows to isolate two types of POM: (1) free POM and (2) POM occluded in soil aggregates. POM fractions are closely linked to their biochemical function for the formation and stabilization of aggregates, therefore methods using different aggregate sizes may result in different POM fractions isolated. We evaluated two physical fractionation procedures to reveal whether they yield different POM fractions with respect to amount and composition, using grassland and arable soils with sandy-loam to sandy,clay-loam texture and thus low macroaggregate stability. Method I used air-dried aggregates of <2.0 mm size and a low-energy sonication for aggregate disruption, method II used field-moist aggregates <6.3 mm and a high-energy,sonication procedure for aggregate disruption. POM fractions were analyzed by elemental analysis (C, N) and CPMAS 13C-NMR spectroscopy. With both methods, about similar proportions of the SOM are isolated as free or occluded POM, respectively. The free- and occluded-POM fractions obtained with method I are also rather similar in C and N concentration and composition as shown by 13C-NMR spectroscopy. Method II isolates a free- and occluded-POM fraction with significantly different C and N concentrations. NMR spectra revealed significant differences in the chemical composition of both fractions from method II, with the occluded POM having lower amounts of O-alkyl C and higher amounts of aryl C and alkyl C than the free POM. Due to the use of larger, field-moist aggregates with minimized sample pretreatment, two distinctly different POM fractions are isolated with method II, likely to be more closely linked to their biochemical function for the formation and stabilization of aggregates. High-energy sonication as in method II also disrupts small microaggregates <63 µm and releases fine intraaggregate POM. This fraction seems to be a significant component of occluded POM, that allows a differentiation between free and occluded POM in sandy soils with significant microaggregation. It can be concluded, that microaggregation in arable soils with sandy texture is responsible for the storage of a more degraded occluded POM, that conversely supports the stabilization of fine microaggregates. Ein Vergleich zweier Methoden zur Isolierung von freier und okkludierter partikulärer organischer Substanz Partikuläres organisches Material (POM) wird im Hinblick auf die Landnutzung als sensitive Fraktion der organischen Bodensubstanz (SOM) angesehen, aber die unterschiedlichen Methoden seiner Isolierung erschweren den Vergleich zwischen verschiedenen Studien. Wir haben zwei physikalische Fraktionierungsmethoden ausgewertet, um zu zeigen, ob sie im Hinblick auf Menge und Zusammensetzung zu unterschiedlichen POM-Fraktionen führen. Hierfür wurden Proben von Grünland- und Ackerböden verwendet. Für Methode I wurden luftgetrocknete Aggregate der Größe <2 mm verwendet, zu deren Zerstörung eine Ultraschallbehandlung mit geringem Energieeintrag eingesetzt wurde. Für Methode II wurden feldfeuchte Aggregate der Größe <6.3 mm und eine Ultraschallbehandlung mit vergleichsweise hoher Energie zur Aggregatzerstörung herangezogen. Mit beiden Methoden konnten zwei POM-Gruppen gewonnen werden: (1) freies POM und (2) in Bodenaggregaten eingeschlossenes POM. Die POM-Fraktionen wurden mittels Elementanalyse (C, N) und CPMAS- 13C-NMR,Spektroskopie untersucht. Methode I zeigte im Hinblick auf Menge und Zusammensetzung nur sehr geringe Unterschiede zwischen freien und okkludierten POM-Fraktionen. Methode II isolierte freie und okkludierte POM-Fraktionen mit signifikant unterschiedlichen C- und N-Konzentrationen. Auch die NMR-Spektren zeigten Unterschiede in der chemischen Zusammensetzung der mit Methode II gewonnenen Fraktionen, die sich in signifikant geringeren O-Alkyl-C-Gehalten bei höheren Aryl-C- und Alkyl-C-Gehalten des okkludierten POM nachweisen ließen. Die Verwendung von größeren, feldfeuchten Aggregaten und die Minimierung der Probenvorbehandlung führt zu einer besseren Differenzierung beider POM-Fraktionen, die wahrscheinlich ihre biologische Funktion besser widerspiegelt. Zusätzlich führt eine Ultraschall-Behandlung mit hohem Energieeintrag zur Zerstörung von kleinen Mikroaggregaten <63 µm und damit zur Freisetzung von feinem Intraaggregat-POM. Diese Fraktion scheint in sandigen Böden mit niedriger Makroaggregat-Stabilität aussagekräftiger zwischen freier und okkludierter POM unterscheiden zu können. Folglich ist eine an das Bodenmaterial angepasste Probenvorbehandlung und Fraktionierungsmethode entscheidend, um eine präzise Charakterisierung der POM-Fraktionen zu gewährleisten. [source] Crystallographic rationalization of the reactivity and spectroscopic properties of (2R)- S -(2,5-dihydroxyphenyl)cysteineACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Gabriele Kociok-Köhn At 150,K, the title compound, C9H11NO4S, crystallizes in the orthorhombic form as a zwitterion and has a low gauche conformation [, = ,46.23,(16)°] for an acyclic cysteine derivative. A difference in bond length is observed for the alkyl C,S bond [1.8299,(15),Å] and the aryl C,S bond [1.7760,(15),Å]. The ,NH3+ group is involved in four hydrogen bonds, two of which are intermolecular and two intramolecular. The compound forms an infinite three-dimensional network constructed from four intermolecular hydrogen bonds. Characterization data (13C NMR, IR and optical rotation) are reported to supplement the incomplete data disclosed previously in the literature. [source] Dichloro[1,1,-(5,9-dithia-2,12-diazoniatrideca-1,12-diene-1,13-diyl)dinaphthalen-2-olato-,2O,O,]dimethyltin(IV) acetonitrile solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2003Stanley A. Bajue Reaction of the potentially hexadentate ligand 1,9-bis(2-hydroxy-1-naphthalenemethylimino)-3,7-dithianonane with dimethyltin chloride gave the title 1:1 adduct, in which the long ligand wraps around the SnCl2Me2 unit and in which the stereochemistry is fully trans. This compound crystallizes from acetonitrile as the 1:1 solvate [Sn(CH3)2(C29H30N2O2S2)Cl2]·C2H3N. During the reaction, the hydroxyl protons move to the N atoms. Most of the chemically equivalent bond lengths agree to within experimental uncertainty, but the Sn,Cl bond that is inside the ligand pocket is substantially longer than the Sn,Cl bond that points away from the long ligand [2.668,(1) versus 2.528,(1),Å]. The O,Sn,O angle is 166.0,(1)°. Comparison of the Sn,O, C,O and aryl C,C bond lengths with those of related compounds shows that the most important resonance forms for the Schiff base aryloxide ligand are double zwitterions, but that the uncharged resonance forms having carbonyl groups also contribute significantly. [source] | ||||||||||