Methyl 3,3,3-trifluoropyruvate hemiaminals: Stability and transaminations

Hemiaminals of methyl 3,3,3-trifluoropyruvate with aromatic amines, benzylic monoamines and diamines were prepared and their interconversions studied using NMR spectrometry. In solution, benzylic hemiaminals were found to be stable in contrast to aromatic hemiaminals, which, in turn, were stable in the solid state.     

1H-NMR study of Na alginates extracted from Sargassum spp. in relation to metal biosorption

The use of a number of species of marine brown algae in the implementation of bioremediation strategies for toxic heavy metals is being considered and evaluated. The biosorption capacity of these algae for heavy metals resides mainly in a group of linear polysaccharides known as alginates that occur as a gel in the algal thallus. The potential for selective metal binding by the biomass of two species of Sargassum was evaluated by ¹H-NMR (nuclear magnetic resonance) following a high temperature, alkaline extraction and purification of their alginate polysaccharide. The alkaline extraction protocol applied to Sargassum fluitans and Sargassum siliquosum yielded alginate samples of low viscosity, suitable for direct acquisition of well-resolved spectra. Estimates of both the ratio of β-d-mannopyranuronosyl (M) and α-l-gulopyranuronosyl (G) residues along the polymer chain and the frequencies of occurrence of diad uronic acid residue pairs were obtained. Guluronic acid (G) was the major component in all, extracts and the GG diads accounted for more than 49% of the polymer diads. Whereas the performance of Sargassum spp. in the metal biosorption process is a function of both its alginate content and composition, the occurrence of “G-blocks” in both purified alginates and in the raw brown seaweed is critical because it results in a well-established selectivity for divalentions, potentially increasing the commercial effectiveness of targeted biosorption as a means of remediation.     

Diphosphacarborane analogues of ferrocene: the synthesis of two isomeric twelve-vertex closo-[(eta5-C5H5)FeP2CB8H9] complexes

The reaction of the Tl+ salt of the [nido-7,8,9-P2CB8H9]- anion (1-) with [CpFe(CO)2I](Cp =eta(5)-C5H5) in refluxing mesitylene for 12 h gives mixed-sandwich [1-Cp-closo-1,2,3,4-FeP2CB8H9] (2) (yield 63%). Reaction of the PPh4+ salt of the isomeric [nido-7,8,10-P2CB8H9]- anion 3- with [CpFe(CO)2I] in refluxing mesitylene gives [1-Cp-closo-1,2,3,5-FeP2CB8H9]4 (yield 56%), isomeric with 2. Compound 4 also results (yield 92%) from the sublimation of 2 under argon at ca. 350 degrees C. The constitution of all compounds is established by mass spectrometry, IR spectroscopy and multinuclear NMR spectroscopy (1H, 11B, 31P, and 13C; two-dimensional [11B-11B]-COSY, and 1H- 11B(selective)), further confirmed in the case of 4 by a single-crystal X-ray diffraction analysis.     

Studies on hydrolyzable carbides. XXII: The carbothermal reduction of scandium oxide Sc2O3

The composition of the products of carbothermal reduction of Sc₂O₃ is examined by X-ray diffraction and chemical analysis and by the hydrolysis method. At pressures of 10^–2-1 Pa, the reaction starts in the temperature region of 1 000–1 200°C. The first product is Sc₂OC of NaCl type; at 1 Pa and 1 400–1 500°C this substance is formed quantitatively (according to stoichiometry) within 50–100 h, repeated homogenization, however, is necessary, or else Sc₂OC reacts locally with Sc₂O₃ giving Sc₂O_1+x C_1–x . The lattice parameter of Sc₂OC in the presence of Sc₁₅C₁₉ is 457.6₃pm. At temperatures above 1 500°C, Sc₁₅C₁₉ is incompletely formed by subsequent reaction with carbon. The product melts at cca. 1 800°C; carbon dissolves and the final composition approaches ScC₂. Carbon separates during solidification. The phase fractions in the products are affected by evaporation, the vapour pressures above both Sc₂OC and Sc₁₅C₁₉ being comparable with the pressure requisite for the carboreduction process. The results are discussed with respect to the often ambiguous published data.

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Untersuchung hydrolysierbarer Carbide, XXII. Die karbothermische Reduktion von Scandiumoxid

Zusammenfassung Zur Untersuchung von Produkten der karbothermischen Reduktion von Scandiumoxid wurden sowohl röntgenographische und chemische Analyse als auch die hydrolytische Methode verwendet. Bei 10^–2 bis 1 Pa beginnt die Reaktion im Temperaturintervall von 1 000–1 200°C. Das erste Reaktionsprodukt ist das Scandiumoxidcarbid Sc₂OC von NaCl-Typ, das quantitativ (der Stöchiometrie entsprechend) bei 1 400–1 500°C und 1 Pa in 50–100 Stunden entsteht. Eine wiederholte Homogenisierung ist allerdings notwendig, damit es zu keiner lokalen Reaktion zwischen Sc₂OC und Sc₂O₃ kommt, bei der dann die Phase Sc₂O_1+x C_1–x entsteht. In Gegenwart von Sc₁₅C₁₉ ist der Gitterparameter von Sc₂OCa=457.6₃pm. Über 1 500°C führt eine weitere Reaktion mit Kohlenstoff zu einer nicht ganz vollendeten Bildung von Sc₁₅C₁₉. Bei cca. 1 800°C schmilzt das Reaktionsprodukt bei gleichzeitiger Auflösung von weiterem Kohlenstoff und die Zusammensetzung nähert sich der Formel ScC₂, beim Erstarren fällt der Kohlenstoff wieder aus. Die Verteilung der Phasen im Produkt wird von der Verdampfung beeinflußt, da die Dampfdrucke von Sc₂OC und Sc₁₅C₁₉ mit dem zum Karboreduktionverlauf notwendigen Druck vergleichbar sind. Die erhaltenen Ergebnisse werden in Relation mit den nicht eindeutigen Angaben in der Literatur diskutiert.

     

Reaction of (Z)-narceine imide with 1,2-epoxypropane

Summary (Z)-Narceine imide (1) reacted with 1,2-epoxypropane to narceone imide (2) and with an excess of epoxide to N-(2-hydroxypropyl)narceone imide (3). Cyclization of3 in acidic media afforded two isomers of 8,14-dimethyl-11,12-methylenedioxy-3,4,10-trimethoxyindano[1,2:2,3]morpholino[3,4-a]isoindolin-5-ones16 and17 which differed in the spatial orientation of the C-8-CH₃. Narceonic acid (18) cyclized into the isochroman-3-spiro-3-phthalide derivative19.

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Reaktion des (Z)-Narceinimid mit 1,2-Epoxypropan

Zusammenfassung (Z)-Narceinimid (1) reagierte mit 1,2-Epoxypropan zu Narceonimid (2) und bei Überschuß von Epoxid zu N-(2-Hydroxypropyl)narceonimid (3). Cyclisierung der letztgenannten Verbindung in Anwesenheit von Mineralsäuren fürhrte zu zwei Indano[1,2:2,3]morpholino[3,4-a]isoindol-5-on-Isomeren16 und17. Narceonsäure (18) wurde zu dem Isochroman-3-spiro-1-phthalid19 umgewandelt.

     

One-pot reaction as an efficient method for rigid molecular tweezers

Rigid molecular tweezers are compounds of increasing scientific interest. As the structural requirements for such compounds are highly specific, few types of these tweezers are thus far known. The preparation of examples of rigid large-pincered molecular tweezers based on bis Troger's bases derived from 1,4-benzenediamine is described. In addition, evidence is presented of the different binding abilities of the diastereoisomers of such compounds.     

Hydroxil and iron ions in YAP: Er laser crystals

⁴S_3/2⁴I_9/2 (1.663m) and⁴I_11/2⁴I_13/2 (2.731m) laser transitions in YAPEr were studied using a material containing Fe, hydroxil impurities and other codopants. Iron impurity causes luminescence quenching of both the⁴S_3/2 and⁴I_11/2 levels whereas OH^– ions enlarge losses, particularly at 2.731m. The effect of iron and hydroxil impurities may be easily diminished by adding Mg²⁺ ions, whereas the admixture of Ce³⁺ or Zr⁴⁺ brings no positive effects.     

A new polymorph of succinylcholinium diiodide: comparison of succinylcholinium structures

The title compound {systematic name: trimethyl[2‐({4‐oxo‐4‐[2‐(trimethylazaniumyl)ethoxy]butanoyl}oxy)ethyl]azanium diiodide}, C₁₄H₃₀N₂O₄²⁺·2I⁻, is a salt of the succinylcholinium cation. There is one formula unit in the asymmetric unit, represented by two anions and two halves of two cations which lie on centres of inversion. The component species are stabilized by electrostatic interactions, and C—H...I and C—H...O hydrogen bonds are also present.     

Segmented sediment probe for diffusive gradient in thin films technique

A new modification of a constrained sediment probe was tested for application in the diffusive gradient in thin films technique (DGT). The sediment probes packed with agarose based resin and diffusive gels were exposed under laboratory conditions to well-mixed test solutions of cadmium and nickel as model elements. The reproducibility of metal uptake in segments (strips) of resin gel with anchored 8-hydroxyquinoline functional groups (Spheron-Oxin? ion exchanger) was studied. The relative yield of uptake of metals in resin gel strips, determined as the ratio of the time-averaged DGT-measured metal concentration and the concentration of a metal in the test solution, showed that the effective sampling area was larger than the geometric area of the resin gel strip. This relative yield is in very good agreement with the theoretical value obtained by the Finite Element Method (FEM) in calculation of diffusion processes. The performance of the modified constrained probe is demonstrated by an example of uranium, iron and manganese depth profiling in a spiked sediment core. Utilization of the new segmented sediment probe in the DGT technique is very simple. Its application does not require special devices and labor-intensive procedures. It can provide sediment depth profiles of metals with the resolution down to the millimetre level.