Oberflächenzusammensetzung,Löslichkeit und Ionenaktivitätsprodukt von Calcit in fremdionenhaltigen Lösungen

Surface Composition, Solubility, and the Ion Activity Product of Calcite in Solutions with Auxiliary Ions Using the method of simultaneous ion and isotope exchange the chemical composition of the surface layer of calcite powder in equilibrium with solutions of varying Me/Ca molar ratios is determined (Me = Mg²⁺, Co²⁺, Ni²⁺, and Fe²⁺ ions). The ion exchange isotherms show a marked bend in the surface reactivity when a surface molar ration of ～1 and ～3 is reached. The solubility of calcite initially decreases on the addition of Co²⁺ or Ni²⁺ ions to the solution whereas it increases in the presence of Mg²⁺ or Fe²⁺ ions. The activity product of the pseudo compound, Ca_xMe_(1–x)CO₃, decreases in the Ni²⁺, Co²⁺ or Fe²⁺ exchange experiments, however, it increases considerably in those with Mg²⁺ ions.     

Zur Thermodynamik der Metallcarbonate 3. Mitteilung [1]. Löslichkeitskonstanten und Freie Bildungsenthalpien von ZnCO3 und Zn5(OH)6(CO3)2 bei 25°

The solubilities of ZnCO₃ and Zn₅(OH)₆(CO₃)₂ have been investigated at 25°C in solutions of the constant ionic strength 0,2 M consisting primarily of sodium perchlorate. From experimental data the following values for equilibrium constants and GIBBS free energies of formation are deduced: A predominance area diagram for the ternary system Zn²⁺–H₂O–CO_2(g) including ZnO, ZnCO₃, Zn₅(OH)₆(CO₃₎₂, and Zn²⁺ is given.     

Photochemische Reaktionen. 62. Mitteilung [1]. Die Photofragmentierung von O-acetyljervin

On ultraviolet irradiation O-acetyljervine ( 1 ) is subjected to several parallel fragmentations. From the complex reaction mixtures obtained in a variety of solvents (dioxan, tetrahydrofuran, acetonitrile, iso-octane, benzene) the major alicyclic products 6 – 8 and the heterocyclic compounds 12 – 16 have been isolated. Products 6 – 8 undergo further photochemical changes, e.g., decarbonylation of 7 to 9 and hydrolytic cleavage of 8 to 10 . These photofragmentations are initiated almost specifically upon selective π → π* excitation at 2537 Å with a quantum yield of Φ²⁵³⁷ = 0.145 for conversion of starting material. Reaction upon irradiation in the long-wavelength n → π* absorption band is very much less efficient (Φ³⁶⁶⁰ = 0.611 · 10^?3, both determinations for O-trimethylsilyl-jervine ( 2 ) in tetrahydrofuran). A high degree of photostability is observed also at 2537 Å on N-protonation of O-acetyljervine ( 1 ) in acetic acid. Furthermore, reactivity is greatly reduced for the N-methyl ( 3 ) and N-acetyl ( 4 ) derivatives in neutral solvents at 2537 Å. N-Chloro-O-acetyljervine ( 5 ) in dioxan at 2537 Å gave preferentially O-acetyljervine hydrochloride.     

Steroide und Sexualhormone. 238. Mitteilung [1]. Die Synthese von 14βO, 18N-Ep (oxyäthanoimino)-Steroiden

The synthesis of the title compound 3 is described. The reaction sequence will serve as a model for a partial synthesis of batrachotoxinin A ( 2 ).     

Photochemische Reaktionen. 50. Mitteilung [1]. Zur Photochemie von gesättigten β-Ketosulfiden II. Synthese von 6-Hydroxy-2-thia-7-oxa-isotwistan

The results of the ultraviolet irradiation of the saturated β-ketosulfide 2 are discussed. The photochemistry of 2 is characterized by the occurrence of two primary photoprocesses. Their efficiences depend markedly on the excited transition, (charge-transfer)- or (n → π*)-excitation, respectively. In methanol solution (charge-transfer)-excitation leads almost exclusively to product 7 , due to (C_α – S)-fission, and (n → π*)-excitation to nearly equal amounts of 7 and of products 4 and 6 which result from α-cleavage. On solvent sensibilization in benzene products 4, 6, 7 and the still unidentified product 5 ² are formed. Compounds 4 and 6 have been described earlier [2]. The structure elucidation of 7 is reported in this paper. Acid-induced transformation of 7 yields the dihetero-isotwistane 15 .     

Chemischer Transport fester Lösungen. 24 [1] Bildung von Mischphasen und chemischer Transport im System MnO/MnS

Chemical Vapor Transport of Solid Solutions. 24. [1] Formation and Chemical Vapor Transport of MnO/MnS mixed Crystals In the System MnO/MnS mixed crystals MnS_1?xO_x (x = 0 …0,04) are formend. By means of CVT methods using bromine as transport agent (1000 → 900 °C) MnO, MnS and MnS:O‐mixed phases could be obtained. The role of traces of water is discussed.     

Über basische Aluminiumsalze und ihre Lösungen. VII. Zum Einfluß der Herstellungsbedingungen,der Konzentration und der Alterungszeit auf die Zusammensetzung von Lösungen basischer Aluminiumsalze

Basic Aluminium Salts and their Solutions. VII. Influence of Preparation, Concentration, and Aging on the Constitution of Solutions of Basic Aluminium Salts 0.1 to 4 molar basic aluminium chloride solutions – prepared by dissolving aluminium metal in substoichiometric quantities of hydrochloric acid and 10^?4 to 0.2 molar basic solutions of aluminium chloride and perchlorate – prepared by adding alkali to the solutions of the neutral salts were investigated for the kinetics of their reactions with ferrone and by ²⁷Al NMR spectroscopy. In all solutions the contents of polymeric species decreases at equal basicity with increasing aluminium concentration. On the other hand the Al₁₃O₄₀ complex is only formed in solutions prepared by addition of alkali. The differences of composition are confirmed by the aging behaviour of the solutions.     

Elektronentransfer und Ionenpaar-Bildung. 46. Mitteilung. Titrationen von Tetracyanethen mit Alkali- und Erdalkalimetallen in aprotischen Lösungen

Electron Transfer and Ion-Pair Formation: Titrations of Tetracyanoethene by Alkaline and Alkaline Earth Metals in Aprotic Solution For alkaline and earth alkaline metal ‘titrations’ of the π-acceptor tetracyanoethene in aprotic (c(H^⊕) < 0.1 ppm) solution, UV/VIS and ESR spectra have been measured in a sealed glas apparatus. Isosbestic points prove uniform but differing metal-mirror reduction processes for [Li]_x, [Na]_x, and [K]_x vs. [Cs]_x. The formation of solvent-shared or solvent-separated contact ion pairs detected is supported by subsequent crystallization and structure determination. For the tetracyanoethene radical anion, semiempirical PM3 calculations with limited configuration interaction allow to reproduce the structural data as well as the long-wavelength charge transfer excitation.     

Die Beeinflussung des photochemischen Verhaltens von Farbstoffmolekeln in Lösung durch Fremdsubstanzen. Lösungen von Chinizarin in aliphatischen Kohlenwasserstoffen in Gegenwart aromatischer Verbindungen

The acceleration of the photolysis of several anthraquinone derivatives by admixture of various substances, notably of carbonyl compounds ans lead(IV) salts has been studied in a variety of solvents. The sensitization of the photolysis results from the production of radicals either directly from the irradiated lead salts or from the solvent upon hydrogen atom abstraction by the excited carbonyl compounds, probably in the triplet state. The reaction of these radicals with the dye results in the formation of several derivatives of its leuco form, whose absorption in the visible and ultraviolet closely resemble that of the unsubstituted leuco form. These reactions are observed in very dilute solutions, in which intermolecular energy transfer is not expected to occur.     

UV-VIS- und Raman-spektroskopische Untersuchungen der grünen Lösungen von Stickstofftriiodid-1-Pyridin in Pyridin

UV-VIS-Spectroscopical Investigations of the Green Solutions of Nitrogen Triiodide-1-Pyridine in Pyridine Solid, crystalline nitrogen triiodide-1-pyridine has a polymeric structure similar to that of nitrogen triiodide-1-ammonia consisting of NI₄ tetrahedra linked to chains by common vertices. The solubility of both compounds in liquid ammonia is accomplished by a degradation of the chains involving protolysis equilibria with monoiodamine. UV-VIS-spectra of the green solutions of NI₃ pyridine in the aprotic solvent pyridine between ?30 and ?16°C and Raman-spectra of these solutions at ?30°C or quenched with liquid nitrogen at ?196°C show, that the chains are retained here at least to some extent. The solutions are instable even at low temperatures and decompose in a first order reaction yielding nitrogen and iodine. The halflife period at ?16°C is 5 hours, at ?30°C 20 hours.     

Über Pterinchemie. 59. Mitteilung [1]. Konformationsanalyse von acylierten 5,6,7,8-Tetrahydropterinen

Conformational Analysis of Acylated 5,6,7,8-Tetrahydropterines The conformation of N(5)-acetates, and of N(5)- and N(8)-trifluoroacetates, respectively, of 6-methyl- and cis-6, 7-dimethyl-tetrahydropterines is studied by ¹H-NMR. spectroscopy. It is shown that the methyl group next to the acylated nitrogen atom is in quasi-axial position.     

Über die Hydrolyse von Eisen(III)Salzlösungen. I. Die Hydrolyse der Lösungen von Eisen(III)chlorid

When a very diluted iron(III)chloride solution is slowly alkalified by a weak base, the deprotonation of [Fe(H₂O)₆]³⁺ proceeds in a first stage to form mono- and dinuclear hydroxoaquo-complexes. In a second stage 4 dimers condense around a chloride ion to form an eight membered ring, an embryon, which grows fast to very small crystals of the composition Fe₄O₃(OH)₅Cl and the structure of the β-FeOOH. These crystalline micells remain colloidally dissolved. If the pH is raised above approximately 3.4 the Cl^?- are exchanged against OH^?-ions and flocculation occurs. This shows that Pauli, assuming the micells of such sols to be polynuclear complex ions, is basically correct, and it follows that micells can also be micro-crystals. When an iron(III)chloride solution is neutralized fast with a strong base, an ‘amorphous’ precipitation is obtained which gives with MoK_α-X-rays only two broad reflections, showing that the iron oxide hydroxide octahedra are condensed in a highly disordered way. The coherently scattering areas of this precipitate are probably tetramers. Small amounts of primarily formed amorphous iron(III)hydroxide are transformed into β-FeOOH.     

Photochemische Reaktionen. 76.Mitteilung [1]. UV.-Bestrahlung von 11-Oxo-Steroiden V Die Photoisomerisierung von 3,20-Diäthylendioxy-5α,14β,17α-pregnan

The UV.-isomerisation of 11-oxo-14β,17α-pregnane 9 to the 11,19-cyclo-derivative 11 is described. In addition the Pb(OAc)₄-fragmentation of photoproduct 11 was investigated. 11 yielded besides the expected 11-oxo-19-hydroxy-pregnane 18 the novel 9,11-seco-11,19-cyclosteroid 19 . The structure of 19 was established by chemical transformations and subsequently confirmed by X-ray analysis [2].     

Synthese von (±)-α-Chamigren. Vorläufige Mitteilung

Synthesis of (±)-α-Chamigrene Cis- and trans-β-ionol (cis and trans- 1 ) underwent acid catalysed dehydration to a mixture of the tetraenes 2–5 in 70–80% yield (Table 1). Irradiation of this mixtures made the 6-(Z), 8-(Z)-isomer 5 accessible (columns 3 and 4 in Table 1). Pyrolysis of the different mixtures at 170° showed, that both isomers, 3 and 5 respectively undergo electrocyclization to dehydrochamigrene ( 6 ). The latter was reduced to α-chamigrene ( 7 ) by hydrogen on Lindlar catalyst.