Gisela Ohms

A simple method to distinguish between polyphosphate and other phosphate fractions of activated sludge

Abstract A procedure of sequential extraction steps proposed by Psenner et al. ( Arch. Hydrobiol. Suppl. 70 ,111–155, 1984; Arch. Hydrobiol. Beih. Ergebn. Limnol. 30 ,98–103, 1988) to quantify ecologically relevant phosphate fractions in lake sediments has been applied to activated sludge from waste treatment plants for biological phosphate removal. By this method, the following phosphate fractions of technological significance may be distinguished: (a) redox-sensitive phosphate, mainly bound to Fe(OH) 3 ; (b) phosphate adsorbed to surfaces (Al 2 O 3 ), exchangeable against OH − , and alkali-soluble phosphate; (c) phosphate bound to CaCO 3 , MgCO 3 and in apatite; and (d) a fraction which hitherto has been designated as “organically bound phosphate”. By means of nuclear magnetic resonance spectroscopy and by inclusion of a hot water extraction step it became evident that fraction (d) mainly contained polyphosphate (PP). In activated sludge samples with phosphate-accumulating bacteria, the PP content amounted to 80 mg/g MLVSS. By combination of the Psenner fractionation and hot water extraction, indications of a significant proportion of PP in lake sediments have also been found.

Solid‐state NMR of bisphosphonates adsorbed on hydroxyapatite

Solid‐state 31P and 13C magic angle spinning (MAS) NMR spectra were used to characterize pure bisphosphonates and also bisphosphonates adsorbed on hydroxyapatite. Four geminal bisphosphonates, including the clinically used compounds ethane‐1‐hydroxy‐1,1‐diphosphonic acid, 3‐amino‐1‐hydroxypropane‐1,1‐diphosphonic acid and 4‐amino‐1‐hydroxybutane‐1,1‐diphosphonic acid, five α,ω‐bisphosphonates and phosphonoacetic acid were investigated. NMR spectra of pure and adsorbed bisphosphonates differ in the observed linewidths and in the isotropic chemical shifts. The broad lines reflect mainly the poor crystallinity of the adsorbed compounds. Shifts of δiso in both directions do not reveal a correlation with the molecular structures. The molar ratio of phosphonates adsorbed on hydroxyapatite determined by 31P spectra without cross‐polarization (CP) is approximately two times larger for geminal bisphosphonates than for α,ω‐bisphosphonates and phosphonoacetic acid. 13C CP/MAS spectra of pure and adsorbed bisphosphonates recorded in two cases for identification of adsorbed compounds give additional information about the state of adsorbed compounds. Disodium α,ω‐dihydroxypolymethylene‐α,ω‐bisphosphonates in the solid state show characteristic 13C chemical shifts which are indicative of either odd or even numbers of CH2 groups. Copyright

Diselenadiphosphetandiselenide und Triselenadiphospholandiselenide - Synthese und Charakterisierung mittels31P- und77Se-Festkörper-NMRSpektroskopie

1,3-Diselena-2,4-diphosphetan-2,4-diselenide, (RPSe2)2, mit R = Me, Et, t-Bu, Ph, 4-Me2NC6H4, 4-MeOC6H4 wurden nach verschiedenen Methoden hergestellt. Von den unloslichen Verbindungen wurden 31P- und 77Se-CP-MAS-Seitenbandspektren aufgenommen. Auf diese Weise konnte die Reinheit kontrolliert und an Hand der isotropen und anisotropen Werte der chemischen Verschiebungen sowie der Kopplungskonstanten 1JP–Se die Struktur der untersuchten Verbindungen bewiesen werden. Auserdem wurden zwei unter ahnlichen Synthesebedingungen entstehende 1,2,4-Triselena-3,5-diphospholan-3,5-diselenide, (RPSe2)2Se (R = Me, Et), untersucht, von denen die Struktur sowohl aus den 77Se-Satelliten der 31P-Losungsspektren als auch aus Festkorperspektren abgeleitet wurde. Am Beispiel von (t-BuPSe2)2 wurden die experimentell aus den Seitenbandspektren ermittelten Hauptachsenwerte der Phosphor- und Selen-Abschirmtensoren mit den aus IGLOBerechnungen (HF und SOS-DFPT) erhaltenen Werten verglichen und die aus den Berechnungen ermittelten Hauptachsenlagen diskutiert. Diselenadiphosphetane Diselenides and Triselenadiphospholane Diselenides – Synthesis and Characterization by 31P and 77Se Solid-State NMR Spectroscopy 1,3-Diselena-2,4-diphosphetane-2,4-diselenides (RPSe2)2 with R = Me, Et, t-Bu, Ph, 4-Me2NC6H4, 4-MeOC6H4 have been synthesized by different methods. The insoluble compounds were investigated by 31P and 77Se solid-state NMR and the purity of the compounds has been checked by their CP MAS sideband NMR spectra. The structure of the investigated compounds has been confirmed by the isotropic and anisotropic values of the chemical shifts and the 1JP–Se coupling constants. In addition, two new 1,2,4-triselena-3,5-diphospholane-3,5-diselenides, (RPSe2)2Se (R = Me, Et), formed under similar synthesis conditions, were investigated. Their structure was derived from the 77Se satellites of 31P solution spectra and from solid-state spectra. For (t-BuPSe2)2 the experimentally obtained principal values of phosphorus and selenium shielding tensors are compared with values from IGLO calculations (HF und SOS DFPT). The calculated orientations of the principal axes are discussed.

DIE STRUKTUR VON ALKYL- UND ARYLPERTHIOPHOSPHONSÄUREANHYDRIDEN IN LOSUNG

Abstract The analysis of 1H-, 31P- and 13C-NMR spectra of different alkyl- and arylperthiophosphonic acid anhydrides shows that these compounds prefer a dimeric structure in solution. They exist as 2,4-diorganyl-2,4-dithioxo-1,3,2λ5,4λs-dithiadiphosphetanes. Most of the perthiophosphonic acid anhydrides form configuration isomers which differ in the position of the thioxo groups relatively to the ring plane. The concentration of the trans-isomer is generally larger than that of the cis-isomer. The ratio of the concentration of both isomers is obviously determined by the polarity of the solvent used. Mixing of solutions of different perthiophosphonic acid anhydrides results in unsymmetrical compounds also existing in cis- and trans-configuration. 31P chemical shifts and geminal P-P coupling constants for symmetrical and unsymmetrical perthiophosphonic acid anhydrides are presented and discussed.

TARANAKITE : THE MINERAL WITH THE LONGEST CRYSTALLOGRAPHIC AXIS

For the first time large single-crystals of taranakite K3Al5(HPO4)6(PO4)2·18H2O were grown by gel crystallization. An X-ray structure determination showed taranakite to be the mineral with the longest crystallographic axis described hitherto. X-ray crystal data are: space group R3c, a = 870.25 (11), c = 9505(1)_pm, Z = 6, Rg = 0.028. A neutron scattering experiment with subsequent Rietveld refinement of the powder pattern of deuterated taranakite elucidated the D-atom positions. Neutron crystal data are: a=868.82(3), c=9498(2) pm, Rwp=0.061. Taranakite is a layer structure mineral having six layers of composition [K3Al5(HPO4)6(PO4)2(H2O)12] separated from each other by water layers. The rigid layer is formed by columns of corner sharing hydrogen phosphate tetrahedra and Al octahedra which are interconnected by additional six-coordinated Al ions. In trigonal holes of the layer orthophosphate ions are situated. Non-exchangeable K ions are trapped within the layers. Hydrogen bonds in taranakite are formed between building units within the rigid layer, within the water interlayer, and between layer and interlayer. Similarities and differences between the coordination of interlayer water in taranakite and ice Ih are discussed. 31P solid-state MAS NMR spectra show two isotropic lines at σ180 = −17.2 and 5.2 ppm. The intensity ratio 3:1 of the two sideband systems corresponds to the molar ratio of HPO42− and PO43− units in the structure of taranakite. The P(1) atom of hydrogen phosphate has a larger anisotropy in agreement with the more different PO bond lengths of HPO42− compared to PO43−. The 31P nuclear magnetic shielding tensor of HPO42− is characterized by larger shielding values σ22 and σ33.

Crystal structure, nuclear magnetic resonance spectroscopy and individual gauge for localised orbitals (IGLO) calculations of C6H4P2S6, a new tetrathiadiphosphorinane, and comparison with related P–S compounds

The reaction of 1,2-diphosphinobenzene with sulfur yielded a new constitution of a tetrathiadiphosphorinane ring: 4,6-(1,2-phenylene)-4,6-dithioxo-1,2,3,5,4λ5,6λ5-tetrathiadiphosphorinane the crystal structure of which has been determined, orthorhombic, space group Pbca(no. 61), a= 12.846(4), b= 16.929(7), c= 11.178(6)A and Z= 8. The tetrathiadiphosphorinane ring has a chair structure with axial positions of the 1,2-phenylene carbons and equatorial positions of the terminal sulfur atoms. One molecule per unique volume is an independent structural unit. This is consistent with the fact that the solid-state 31P cross-polarisation magic angle spinning (CP MAS) NMR spectra give two sets of slightly different principal values of the nuclear magnetic shielding tensor. A comparison with the crystal structure and the solid-state NMR data of trans-2,4-diphenyl-2,4-dithioxo-1,3,2λ5,4λ5-dithiadiphosphetane and cis-2,4-(1,8-naphthalenediyl)-2,4-dithioxo-1,3,2λ5,4λ5-dithiadiphosphetane shows that the nuclear shielding does not only depend on the molecular structure. Short intermolecular S ⋯ S distances lead to deshielding effects on the 31P nucleus. Results of individual gauge for localised orbitals (IGLO) calculations of the 31P nuclear shielding of isolated molecules agree, nevertheless, satisfactorily with the experimental principal values and additionally allow the determination of the orientation of the principal axes in the molecular framework. The IGLO calculations indicate that the principal 3 axis for the most shielded principal value lies nearly parallel with the PS bond.

SYNTHESIS AND 31P AND 13C NMR STUDIES OF PYROPHOSPHONIC ACIDS

Abstract Pyrophosphonic acids were prepared by partial hydrolysis of phosphonic acid dichlorides and by de-hydration of phosphonic acids, respectively. The pyrophosphonic acids as well as their ammonium salts were characterized by NMR spectroscopy. The geminal coupling constant 2JPOP was obtained from spectral analysis and its sign was determined by spin tickling experiments. Furthermore, semiempirical quantum chemical calculations of 2JPOP were carried out.

METHYLTRITHIOPHOSPHONIC ACID AND RELATED COMPOUNDS - SYNTHESIS, SOLUTION, AND SOLID-STATE NMR SPECTROSCOPY AS WELL AS SHIELDING TENSOR CALCULATIONS

Abstract Methyltrithiophosphonic acid (1) has been prepared in a pure state. The thermal decomposition of 1 into 2,4-dimethyl-2,4-dithio-1,3,2,4-dithiadiphosphetane (3) proceeds via dimethylpentathiodiphosphonic acid (2), which has been characterized by its 1H and 31P high resolution NMR parameters and by a derivatization reaction with norbornadiene. Solid-state 31P CP MAS spectra of 1, 3, and the related compounds, 3,5-dimethyl-3,5-dithio-1,2,4,3,5-trithiadiphospholane (4), and 3,6-dimethyl-3,6-dithio-1,2,4,5,3,6-tetrathiadiphosphorinane (5), have been measured. The experimentally determined phosphorus anisotropic shielding tensors are compared with results of IGLO calculations. From a comparison of the experimental values with those calculated for different geometry optimized conformations of 1, 4, and 5 structural assignments became possible: In the solid state 1 most probably shows a trans orientation of the H-S-P─S unit, 4 probably realizes a half-chair and 5 a chair conformation, both with bisaxial ...

SOLID-STATE NMR STUDIES AND CRYSTAL STRUCTURE OF THE LAWESSON-REAGENT

Abstract X-ray diffraction of the toluene solvate of the Lawesson reagent, C14H14O2P2S4.C7H3, gives the following crystal data: triclinic, PT (no. 2). a = 6.831 (2), b = 9.393 (3), c = 9.793 (3) A, α = 70.33 (2), β = 83.28 (2). γ = 71.35 (2)°, V = 560.6 A3, Z = 1, and D2 = 1.471 Mg m−3. The bond lengths and angles are very close to those observed in the solvent-free crystals. The toluene molecule is disordered over two positions related by an inversion center. The asymmetric unit consists of half the formula unit. This is consistent with the fact that the solid-state 31P CP MAS NMR spectrum gives one set of principal values of the nuclear magnetic shielding tensor. Similar values were obtained for solvates of other aromatic compounds such as benzene, o-dichlorobenzene, methoxybenzene and p-dimethoxybenzene. A comparison with the data for the solvent-free Lawesson reagent shows that the nuclear shielding depends not only on the molecular structure but can also be influenced by short intermolecular S==S dis...

Trans-cyclohexane-1,2-diphosphonates synthesis, structural and NMR spectroscopic investigations.

Abstract A stereospecific addition of sodium diethylphosphite to cyclohexene-1-phosphonic acid diethyl ester 1 was used to synthesize trans-cyclohexane-1,2-diphosphonic acid tetraethyl ester 2b. Acidolysis of the ester yields the corresponding diphosphonic acid 2a. Dissociation constants pK1-pK4 of 2a were obtained in aqueous solutions by precision potentiometric titration. The molecular structure of solid 2a determined by X-ray diffraction shows a slightly disturbed chair form of the cyclohexane ring and a bisaxial conformation of the phosphonate groups with a P–C–C–P dihedral angle of 143°. Results of molecular modeling of 2a as well as of its anions (with and without consideration of Na+ cations) obtained by semi-empirical MNDO methods and by empirical force field calculations including molecular dynamics are reported. The investigation of organic solutions of 2b and of aqueous solutions of 2a by NMR spectroscopy allows conclusions concerning the conformative state via a Karplus-type relation for the v...