Environmetric modeling and interpretation of river water monitoring data

This environmetric study deals with modeling and interpretation of river water monitoring data from the basin of the Saale river and its tributaries the Ilm and the Unstrut. For a period of one year of observation between September 1993 and August 1994 a data set from twelve campaigns at twenty-nine sampling sites from the Saale river and six campaigns from the river Ilm at seven sampling sites and from river Unstrut at ten sampling sites was collected. Twenty-seven chemical and physicochemical properties were measured to estimate the water quality. The application of cluster analysis, principal components analysis, and apportioning modeling on absolute principal components scores revealed important information about the ecological status of the region of interest:identification of two separate patterns of pollution (upper and lower stream of the rivers);identification of six latent factors responsible for the data structure with different content for the two identified pollution patterns; anddetermination of the contribution of each latent factor (source of emission) to the formation of the total concentration of the chemical burden of the river water.As a result more objective ecological policy and decision making is possible.     

Zur Sauerstoffbestimmung in Zirkonium, Titan und ihren Legierungen durch Hei?extraktion im Tr?gergasstrom

Zusammenfassung Für die O-Bestimmung im Zirkonium, Titan und ihren Legierungen ist beim Arbeiten nach dem Trägergas-Heißextraktionsverfahren die folgende Arbeitsweise zu empfehlen: Sandwich-Technik unter Verwendung von Pt oder Pd als Hilfsmetallen in einem Verhältnis zur Analysenprobe von etwa 101 bei Temperaturen von ca. 1900°C. Die Probeneinwaagen sollen je nach zu erwartender O-Konzentration zwischen etwa 200 und 1000 mg liegen. Für jede Probe ist ein frischer Reaktionstiegel zu verwenden. Die Reproduzierbarkeit des Verfahrens ist über den gesamten hier interessierenden Konzentrationsbereich mit etwa ±3% rel. abzuschätzen. Systematische Fehler treten bei der Untersuchung der unlegierten Metalle nicht auf und sind auch für die Analyse ihrer Legierungen nicht zu erwarten.

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Determination of oxygen in zirconium, titanium and their alloys by heat extraction in carrier gas

For the determination of oxygen in zirconium, titanium and their alloys using the carrier-gas heat extraction process the following conditions are recommended: sandwich technique using Pt or Pd as auxiliary metals in a ratio to the sample of abt. 101 at temperatures of abt. 1900° C. Depending on the oxygen concentration to be expected, the sample weight should be approx. 200 to 1000 mg. Each sample should be analyzed in a fresh crucible. The reproducibility of the procedure may be estimated to ±3% rel. within the total range of concentration of interest here. There are no systematic errors when analyzing the unalloyed metals and are neither to be expected when their alloys are to be analyzed.

     

Synthesis of [4.3.3]Propellanes by Carbenium‐Ion Rearrangement and Their Olfactory Characterization

Treatment of (+)‐sclareolide ( 1 ) with polyphosphoric acid or Eaton's reagent furnished, besides the anticipated cyclopentenone (?)‐ 12 and its isomer (?)‐ 15 , two diastereoisomeric [4.3.3]propellanes (?)‐ 13 and (?)‐ 14 , which possess interesting woody‐ambery odors. The hydrogenated derivative (?)‐ 17 possessed an even more‐powerful odor reminiscent of natural ambergris tincture. Mechanistic insight into this rearrangement was provided by a by‐product 24 of the reaction of sclareolide ( 1 ) with Eaton's reagent. The carbenium ion rearrangement was then employed in the synthesis of four related [4.3.3]propellanes 40 – 43 , illustrating the utility and scope of this reaction. The olfactory properties of the synthesized [4.3.3]propellanes as well as of the original target structures 10, 33 , and 34 , prepared from (?)‐ 12 and (?)‐ 15 , are discussed. Especially the pronounced ambra odor of (?)‐ 17 vividly contradicts the ‘triaxial rule of amber sensation' and provides new insight into the structural requirements for ambra odorants.     

On the Scope of a Prins‐Type Cyclization of Oxonium Ions

The Prins cyclization of an aldehyde 1 with a homoallylic alcohol 2 , affording tetrahydro‐2H‐pyrans 4 via the oxonium ion 3 as central intermediate, was conceptually transferred to (alk‐3‐enyloxy)acrylates 6 , which form a related oxonium ion 7 upon treatment with acids (Scheme 1). The scope and utility of this modification of the Prins‐type cyclization of oxonium ions is discussed exemplarily by means of the syntheses of ten tetrahydro‐2H‐pyran and tetrahydrofuran derivatives, featuring diverse substitution patterns as well as different degrees of molecular complexity. These target structures include (±)‐ethyl (2RS)‐2‐[(2RS,4SR,6RS)‐ and (2SR,4RS,6SR)‐2‐tetahydro‐4‐hydroxy‐6‐methylpyran‐2‐yl]propanoate ( 23 ), (±)‐ethyl [(2RS, 3RS)‐tetrahydro‐3‐isopropenylfuran‐2‐yl]acetate ( 32 ), (±)‐ethyl (2Z)‐3‐(tetrahydro‐2,2‐dimethylfuran‐3‐yl)acrylate ( 37 ), (±)‐(3aRS,6RS, 7aRS)‐octahydro‐7a‐methylbenzofuran‐6‐yl formate ( 42 ), (±)‐ethyl (2RS,3RS,4aRS,8SR,8aRS)‐hexahydro‐2,5,5,8‐tetramethyl‐7‐oxo‐2H,5H‐pyrano[4,3‐b]pyran‐3‐carboxylate ( 48 ), and (±)‐ethyl (2RS,3RS,6SR)‐tetrahydro‐6‐(2‐methoxy‐2‐oxoethyl)‐3‐methyl‐2H‐pyran‐2‐carboxylate ( 53 ) (see Schemes 3 and 5–8). Besides the stereochemistry and mechanistic details of this versatile oxonium‐ion cyclization, the synthesis of suitable starting materials is also described.     

Ternary Germanides RE 2Ge2Mg (REY, La–Nd, Sm, Gd, Tb)

Summary. The ternary rare earth metal-magnesium-germanides RE₂Ge₂Mg (RE=Y, La–Nd, Sm, Gd, Tb) were synthesized by reaction of the elements in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. The germanides were characterized through their X-ray powder patterns. The structures of Ce₂Ge₂Mg and Pr₂Ge₂Mg were refined from X-ray single crystal diffractometer data: Mo₂FeB₂ type, P4/mbm, a=750.6(1), c=442.4(1)pm, wR2=0.0378, 386 F² values, 12 variable parameters for Ce₂Ge₂Mg, and a=745.7(1), c=439.2(1)pm, wR2=0.0462, 448 F² values, 12 variable parameters for Pr₂Ge₂Mg. The lanthanum compound shows a homogeneity range La_2+xGe₂Mg_1–x. The structure of a single crystal with x=0.249(5) was refined from X-ray data: a=770.52(7), c=447.4(1)pm, wR2=0.0481, 322 F² values, 13 variable parameters. The RE₂Ge₂Mg structures can be considered as a 1:1 intergrowth of CsCl and AlB₂ related slabs of compositions REMg and REGe₂.     

Synthesis and polymerization of 5‐(methacrylamido)tetrazole,a water‐soluble acidic monomer

The reaction of methacryloyl chloride with 5‐aminotetrazole gave the polymerizable methacrylamide derivative 5‐(methacrylamido)tetrazole ( 4 ) in one step. The monomer had an acidic tetrazole group with a pK_a value of 4.50 ± 0.01 in water methanol (2:1). Radical polymerization proceeded smoothly in dimethyl formamide or, after the conversion of monomer 4 into sodium salt 4‐Na , even in water. A superabsorbent polymer gel was obtained by the copolymerization of 4‐Na and 0.08 mol % N,N′‐methylenebisacrylamide. Its water absorbency was about 200 g of water/g of polymer, although the extractable sol content of the gel turned out to be high. The consumption of 4‐Na and acrylamide (as a model compound for the crosslinker) during a radical polymerization at 57 °C in D₂O was followed by ¹H NMR spectroscopy. Fitting the changes in the monomer concentration to the integrated form of the copolymerization equation gave the reactivity ratios r _4‐Na = 1.10 ± 0.05 and r_acrylamide = 0.45 ± 0.02, which did not differ much from those of an ideal copolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4333–4343, 2002     

N,N′,N′′,N′′′‐Tetraethylterephthalamidinium bis(tetrazolate)

The crystal structure of the title 2:1 salt of tetrazole and a substituted terephthal­amidine, C₁₆H₂₈N₄²⁺·2CHN₄^?, contains an infinite network of hydrogen bonds, with short N?N distances of 2.820 (2) and 2.8585 (19) Å between the tetrazolate anion and the amidinium cation. Involvement of the lateral N atoms of the tetrazole in the hydrogen bonding appears to be a typical binding pattern for the tetrazolate anion.