Peroxofluorokomplexe der Übergangsmetalle. IX. Kristallstruktur von Ba3[Ti(O2)F5]2 · 2 H2O

Transition Metal Peroxofluoro Complexes. IX. Crystal Structure of Ba₃[Ti(O₂)F₅]₂ · 2 H₂O The pale yellow hydrat Ba₃[Ti(O₂)F₅]₂ · 2 H₂O crystallizes tetragonal (space group P4₂/mbc, a = 1 248.5(3), c = 812.2(2) pm; Z = 4; R = 0.026 for 404 independent reflections). It contains isolated [Ti(O₂)F₅]^3? anions. Thermal decomposition leads directly to α-Ba₃Ti₂O₂F₁₀, which is isotypic to α-Ba₃Al₂F₁₂.     

Contact angle hysteresis, adhesion, and marine biofouling

Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance.     

Synthesis of Cannabinoid Model Compounds. Part 3. (6aR, 10aR)-N-ethyl-Δ8-tetrahydrocannabinol-18-amide, (6aR, 10aR, 17 RS)-N-ethyl-17-methyl-Δ8- tetrahydrocannabinol-18-amide and (6aR, 10aR)-17,18-didehydro-Δ8-tetrahydrocannabinol

The novel cannabinoids (6aR, 10aR)-N-ethyl-Δ⁸-tetrahydrocannabinol-18-amide (15) and (6aR, 10aR, 17 RS)-N-ethyl-17-methyl-Δ⁸- tetrahydrocannabinol-18-amide (16) , designed as cannabinoid affinity ligands, were synthesized from the corresponding acids 11 and 12 via the N-hydroxysuccinimide esters. Amide 16 was tested in the rat and was generalized to Δ⁹-tetrahydrocannabinol, being 5 times less potent than the training drug. An improved synthesis of (6aR, 10aR)-17,18-didehydro-Δ⁸-tetrahydrocannabinol (23) is reported. As model reaction for the preparation of a tritiated Δ⁸-tetrahydrocannabinol, compound 23 was selectively deuterated at C(17) and C(18) in benzene/Et₃N using [(C₆H₅)₃P]₃RuCl₂ as catalyst.     

Acyl- und Alkylidenphosphane. XXVII [I.]. Molekül- und Kristallstruktur des Methyl[(N-phenyl,N-tri-methylsilyl)thiocarbamoyl]trimethylsilylphosphans

Acyl- and Alkylidenephosphines. XXVII. Molecular and Crystal Structure of Methyl-[(N-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphine . Methyl[(N-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphine 1a formed via an addition of methylbis(trimethylsilyl)phosphine to phenyl isothiocyanate [1], crystallizes in the monoclinic centrosymmetric space group P2₁/n with following dimensions of the unit cell determined at a temperature of measurement of ?80±3°C: a=1041.2(4);b=1706.9(12);c=1001.1(6)pm; β=106.41(4)°; Z = 4. An X-ray structure determination (R_w = 0.039) confirms the constitution of the compound as already derived from its nmr spectra. One trimethylsilyl group is bound to the phosphorus atom, whereas the other is connected with the sp²-hybridized nitrogen atom. Characteristic rounded bond lenghts and angles are: P? Si 231, P? CH₃ 184, P? C(S) 187, C?S 167, N? C(S) 137, and N? Si 181 pm as well as P? C? S 122°, P? C? N 117°, and S? C? N 121°.     

Influence of protein concentration and order of addition on thermal stability of beta-lactoglobulin stabilized n-hexadecane oil-in-water emulsions at neutral pH

The influence of protein concentration and order of addition relative to homogenization (before or after) on the extent of droplet flocculation in heat-treated oil-in-water emulsions stabilized by a globular protein were examined using laser diffraction. n-Hexadecane (10 wt%) oil-in-water emulsions (pH 7, 150 mM NaCl) stabilized by beta-lactoglobulin (beta-Lg) were prepared by three methods: (1) 4 mg/mL beta-Lg added before homogenization; (2) 4 mg/mL beta-Lg added before homogenization and 6 mg/mL beta-Lg added after homogenization; (3) 10 mg/mL beta-Lg added before homogenization. The emulsions were then subjected to various isothermal heat treatments (30-95 degrees C for 20 min), with the 150 mM NaCl being added either before or after heating. Emulsion 1 contained little nonadsorbed protein and exhibited extensive droplet aggregation at all temperatures, which was attributed to the fact that the droplets had a high surface hydrophobicity, e.g., due to exposed oil or extensive protein surface denaturation. Emulsions 2 and 3 contained a significant fraction of nonadsorbed beta-Lg. When the NaCl was added before heating, these emulsions were relatively stable to droplet flocculation below a critical holding temperature (75 and 60 degrees C, respectively) but showed extensive flocculation above this temperature. The stability at low temperatures was attributed to the droplets having a relatively low surface hydrophobicity, e.g., due to complete saturation of the droplet surface with protein or due to more limited surface denaturation. The instability at high temperatures was attributed to thermal denaturation of the adsorbed and nonadsorbed proteins leading to increased hydrophobic interactions between droplets. When the salt was added to Emulsions 2 and 3 after heating, little droplet flocculation was observed at high temperatures, which was attributed to the dominance of intra-membrane over inter-membrane protein-protein interactions. Our data suggests that protein concentration and order of addition have a strong influence on the flocculation stability of protein-stabilized emulsions, which has important implications for the formulation and production of many emulsion-based products.     

Beitrag zur Analyse von Stibin

Zusammenfassung Es wird ein Verfahren zur Bestimmung von Stibin beschrieben, das sich sowohl zur Analyse von SbH₃ in organischen Lösungsmitteln als auch zur Bestimmung von flüssigem oder festem SbH₃ eignet. Hierbei wird das Stibin mit überschüssigem Brom zu Sb^V oxydiert, danach mit SO₂ zu Sb^III reduziert und dieses oxydimetrisch mit Jod oder Bromat titriert.

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Summary A method is proposed for the determination of stibine, applicable to its solutions in organic solvents and also to the solvent-free liquid or solid substance. The procedure involves oxidation of SbH₃ with an excess of bromine to Sb^V, reduction to Sb^III with SO₂, and oxidimetric titration of the trivalent antimony with iodine or bromate.

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Herrn Professor Dr. C. Mahr zum 65. Geburtstag gewidmet.     

Determination of the turnover number of the restriction endonuclease EcoRI using evanescent wave technology

Binding and catalytic activity of the type II restriction endonuclease EcoRI on immobilized DNA has been observed in real time using three different evanescent wave biosensors and two different immobilization techniques. The method gives direct access to the turnover number (kcat) without the necessity for the determination of any concentration or activity. The combination of different evanescent wave techniques gives access to the catalytic mechanism and allows the determination of the rate limiting step.     

Synthesis and x-ray crystal structure of [(THF)Zn(O(2)(OH)SiR)](4) (R = (2,6-i-Pr(2)C(6)H(3))N(SiMe(3))): enroute to larger aggregates

Reaction of aminosilanetriol RSi(OH)(3) (1) (R = (2,6-i-Pr(2)C(6)H(3))N(SiMe(3))) with diethyl zinc at room temperature in 1:1 stoichiometric ratio affords [(THF)Zn(O(2)(OH)SiR)](4) (2) (R = (2,6-i-Pr(2)C(6)H(3))N(SiMe(3))) in good yield. The single-crystal X-ray diffraction studies reveal that 2 is monoclinic, P2(1), with a = 17.117(3) A, b = 16.692(5) A, c = 17.399(4) A, alpha = gamma = 90 degrees, beta = 91.45(7) degrees, and Z = 2. The molecular structure of 2 contains two puckered eight-membered Zn(2)Si(2)O(4) rings, which are connected by the Zn-O bonds and form two planar four-membered Zn(2)O(2) rings. Compound 2 contains an unreacted hydroxyl group on each silicon atom, and hence, we carried out the reactions of 2 with dimethylzinc and methyllithium to form [Zn(4)(THF)(4)(MeZn)(4)(O(3)SiR)(4)] (3) (R = (2,6-i-Pr(2)C(6)H(3))N(SiMe(3))) and [(L)ZnLi(O(3)SiR)](4) (4) (L = 1,4-(Me(2)N)(2)C(6)H(4), R = (2,6-i-Pr(2)C(6)H(3))N(SiMe(3))), respectively. This suggested that 2 could be an intermediate product formed during the synthesis of 3 and 4.     

Chemistry of polyfunctional molecules-123. Reactions of BiBr3, SbI3 and AsI3 with LiN(PPh2)2; X-ray structure of a cyclophosphazene salt containing arsenic(I)

BiBr₃ or SbI₃ react at 20°C with LiN(PPh₂)₂ (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph₂P---N=PPh₂---PPh₂=N---PPh₂ (2). The reaction of AsI₃ with 1 at room temperature formed yellow needles of the eight-membered heterocycle (3), whereas AsI₃ interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI₃ and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt

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I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis.