Kontinuierliche katalytisch-kinetische bestimmung von silber und sulfid im p.p.m.-bereich unter verwendung einer durchflusszelle

The determination of silver and sulphide in the p.p.m. range by a catalytickinetic flow method is described. A flow-through cell is used as the mixing and reaction vessel as well as for measurement. The determination of silver is based on its catalytic action on the oxidation of sulphanilic acid by potassium per-sulphate in the presence of 2,2'-bipyridine. Sulphide retards the catalytic activity of silver and so can be determined indirectly. Interfering ions are studied.     

Organische Phosphorverbindungen XXVIII. Die α-Aminoalkylierung von elementarem weissem Phosphor. Eine einfache Methode zur Darstellung von tertiären Phosphinoxiden,Phosphinsäuren und Phosphonsäuren [1]

White phosphorus reacts with N-hydroxymethyl-dialkylamines to give mainly three products, i.e., tris(dialkylaminomethyl) phosphine oxides, bis(dialkylamino-methyl) phosphinic acids, and dialkylaminomethyl phosphonic acids, according to the equation: The yield of the various products depends mainly upon the ratio of the reactants, the pH, and the solvents used.     

Die verwendung von diisobutylaluminiumhydrid zur stereoselektiven synthese von tertiären (e)-2-alkenylaminen, (e)-2-alken-4-inylaminen und 2(

In exploring versatile synthetic routes to (E)-allylamine derivatives with antimycotic properties, a new method has been found in the trans-reduction of tertiary 2-alkinylanunes by diisobutylaluminum hydride (DIBAH). The stereoselectivity of this reaction, which is in contrast to the well-known cis-hydroalumination of disubstituted alkynes, and the regioselectivity have been studied in detail. Tertiary 2-alkinylamines 1 were generally reduced to (E)-2-alkenylamines 2 in toluene at 40°, and tertiary 2,4-alkadiynylamines 3 yielded a mixture of(E)-2-alken-4-ynylamines 4 and 2(E),4(Z)-alkadienylamines 5 in high stereochemical purity. This reduction was clearly different with respect to reactivity and selectivity in comparison with other reactions also proceeding via trans-hydroalumination, namely the lithium aluminum hydride reduction of α-hydroxyacetylenes and the reaction of alkynes with LiAlH(iso-Bu)₂(n-Bu). Tertiary 6-hydroxy-2, 4-alkadiynylamines 10 were reduced to 6-hydroxy-2(E)-alken-4-ynylamines 11 with diisobutylaluminum hydride, whereas on treatment with lithium aluminum hydride 6-hydroxy-4(E)-alken-2-ynylamines 12 were obtained. LiAlH (iso-Bu)₂(n-Bu) did not react with 2-alkinylamine 1a and the 2,4-alkadiynylamine 3a was only monohydroaluminated without discrimination of the two acetylene groups. A possible mechanism for the diisobutylaluminum hydride reduction of 2-alkinylamines is presented.     

Die optische Aktivität von chiralen Dienen,Enonen und α-Diketonen

The ground state and excited states of butadiene, acrolein and glyoxal are calculated by the SCF-CNDO-CI method. The gauche conformers of these molecules, obtained by a twist about the formal C? C single bond, have served as models for the study of the optical activity of dienes, α,β-unsaturated ketones and α- and β-diketones. An analysis of the molecular orbitals of the ground state and of excited states leads to the conclusion that the sign of a Cotton effect is determined primarly by the nodal properties and the helicity of the ground and excited state orbitals [20]. In cyclopentenones the longest wavelength Cotton effect does not obey the rule deduced from the twisted acrolein model. This apparent anomaly is explained on the basis of the altered nodal properties of cyclopentenones as compared to cyclohexenones. Concerning diones, the comparison of experimental CD. and UV. spectra with the calculated data allows the assignment of the five lowest Cotton effects of camphor quinone. It is found that α-diketones have only two singletsinglet transitions in the region from 500 nm to 250 nm. In contrast, the next strong UV. absorption between 220 nm and 190 nm consists of three distinct electronic transitions, the nature of which is discussed. These findings are correlated with the previously calculated [8] symmetry properties and ordering of the energy levels of the ground state and excited states of planar trans and cis glyoxal. From these results the most likely conformations of a number of α-diketons are derived.     

Die «Zip»-Reaktion: Eine neue Ringerweiterungsreaktion. Synthese von 17-, 21- und 25-gliedrigen Polyaminolactamen. 4. Mitteilung über Umamidierungsreaktionen

The Zip-reaction: A New Method for the Synthesis of Macrocyclic Polyaminolactams The 21- and 25-membered aminolactams 11 and 25 were synthesized from the 13-membered lactam 4 . To introduce the ring enlargement unit (a propylamino group) 4 was N-alkylated using acrylonitrile and the resulting product hydrogenated. Repetition of this reaction sequence gave 3 , which was converted in the presence of base in 90% yield to the ring-enlarged macrocyclic base 11 (Scheme 2). In a similar but stepwise synthesis consisting of two separate ring-enlargement reactions 4 was transformed to 11 via 13 (Scheme 4). Introducing three ringenlargement units into 4 the 25-membered aminolactam 25 was synthesized in 84% yield (Scheme 5). The mechanism of the ring-enlargement reaction is given in Scheme 3. In comparison to a zip-fastener or zipper this reaction is called “zipreaction”.     

Zur Chemie und Strukturchemie von Phosphiden und Polyphosphiden. 36. Tetrakaliumhexaphosphid: Darstellung,Struktur und Eigenschaften von α-K4P6 und β-K4P6

Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 36. Tetrapotassiumhexaphosphide: Preparation, Structure, and Properties of α-K₄P₆ and β-K₄P₆ Tetrapotassiumhexaphosphide has been prepared quantitatively by reaction of the elements at 870 K in sealed Nb and Ta ampoules, respectively. Two crystalline modifications are formed: α-K₄P₆ is stable below 850 K, β-K₄P₆ is stable above this temperature. Both compounds are black semiconductors (E_G(α) = 0.55 eV) with metallic lustre. The orthorhombic structures are defect variants of the hexagonal AlB₂ type structures (K₄P₆□₂) and of a different stacking sequence of this type. Characteristic building units are planar isometric P₆ rings, formed by a specific ordering of defects in the partial structure of the major component. The short P? P distances (215.5 pm and 215.0 pm, respectively) are about 30 pm shorter than the distances compared with a single bond (221 pm). They represent one double bond which is delocalized about six bonds or an aromatic 2π-system. The thermal decomposition in tantalum crucibles, the reaction with quartz walls as well as the reaction with benzophenone in monoglyme yields quantitatively K₃P₇. The reaction with RCl ? Me₃SnCl in monoglyme at 223 K results in the formation of P₇R₃ with high yield (75%). Very probably the valence fluctuating hexaphosphene(4) system is formed at 195 K in the primary reaction step (³¹P-NMR, singulett at 473 ppm downfield).     

Substituierte Halogenocarbonylmetallate des Chroms,Molybdäns und Wolframs. IV. Die Kristallstruktur von Tetramethylammonium-Chloropentacarbonylwolframat

Substituted Halocarbonyl Metallates of Chromium, Molybdenum, and Tungsten. IV. Crystal Structure of Tetramethylammonium Chloropentacarbonyltungstate The structure of tetramethylammonium chloropentacarbonyltungstate has been determined from single crystal X-ray data. The compound crystallizes with four formula units in the monoclinic unit cell (space group P2₁/c) of the dimensions a = 1111.3(4) pm, b = 1110.3(4) pm c = 1204.1(3) pm, β = 99.63(3)°, V = 1464.8 × 10⁶ pm³ (R = 0.028). The anion possesses approximately C_4v symmetry with the principal interatomic distances d(W–C(cis)) = 203 pm, d(W–C(trans)) = 197 pm d(W–Cl) = 256.6 pm. No unusual contacts between cation and anion have been found.     

Thermisches Verhalten von Caesiumchloroferraten(III) und Caesiumchloroferrat(III)-Hydraten. II. Die Rehydratation der Zersetzungsprodukte von Cs3[FeCl6] – Eine ramanspektroskopische Untersuchung unter definierter Wasserdampfatmosphäre [1]

The Thermal Behaviour of Caesiumchloroferrates(III) and Caesiumehloroferrate(III) Hydrates. II. The Rehydration of Decomposition Products of Cs₃[FeCl₆] — A Raman Spectroscopic Study under Definite Atmosphere of Water Vapour Cs₃[FeCl₆] formed by dehydration of Cs₃[FeCl₆] · H₂O at about 160°C does not change at normal atmosphere within 3 till 4 hours. Rehydration under the vapour pressure of the eliminated water yields the monohydrate in nearly the same time. In the same manner rehydration of the solid mixture of Cs[FeCl₄] and 2 CsCl formed by thermal decomposition of the metastable Cs₃[FeCl₆] (280°C) produces the intermediates Cs₃[Fe₂Cl₉] and Cs₂[Fe(H₂O)Cl₅] in mixtures with CsCl and, finally, Cs₃[FeCl₆] · H₂O. The formation of Cs₃[Fe₂Cl₉] from Cs[FeCl₄] and CsCl is accelerated by water. The reaction cycle has been studied using Raman and IR spectroscopy. The results will be discussed with respect to thermoanalytical data.     

Craig-Verteilung von Seltenerdnitraten im System Tri-n-Butylphosphat-Salpetersäure, 4. Mitt.: Gemischtrennungen mit Apparaturen von 120 und 160 Elementen; Reindarstellung von Samarium und Gadolinium

Zusammenfassung In einer Apparatur mit 120 bzw. 160 Elementen wurde der Verlauf der präparativenCraig-Verteilung von Yttererdgemischen unter Entnahme der Oberphase bei systematischer Veränderung der Bedingungen untersucht und durch die wirksamen Stufenzahlen und die effektiven Trennfaktoren charakterisiert, für die sich der Tetradeneffekt nachweisen ließ. Die Trennung wurde vor allem im Gebiet Sm-Eu-Gd wesentlich verbessert, bis zu 80% des Einsatzes (60 g) ließen sich reiner als 90 bzw. 99% erhalten; ein großer Teil des La-, Nd- und Sm-oxids fiel bereits reiner als 99,9% an.Aus etwa 99proz. Produkten wurde Sm₂O₃ in einer Reinheit von 99,9 bis 99,99% und Gd₂O₃ reiner als 99,9% erhalten (Ausb. 70 bzw. 58%).

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Craig-distribution of rare earth nitrates in the system tri-n-butyl phosphate-nitric acid, IV: Separation of mixtures using apparatus with 120 and 160 elements, resp. Preparation of pure samarium and gadolinium

Using an apparatus with 120 and 160 elements, resp., the preparativeCraig-distribution of yttrium-earth mixtures by withdrawal of the upper phase was examined on systematic variation of experimental conditions; these were characterized by the number of effective stages and the effective separation factors, which were demonstrated to show the tetrad effect. A much better separation could be achieved especially in the neighborhood of Sm, Eu and Gd; up to 80% of the input (60 g) were collected in a purity better than 90 or 99%, a significant part of La-, Nd- and Sm-oxides was already better than 99.9%.Starting with products of a purity near 99%, Sm₂O₃ resulted in a purity of 99.9–99.99% and Gd₂O₃ better than 99.9% (yield 70 and 58%, resp.).

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Mit 2 Abbildungen     

Zur Reaktionsweise von Diphenylcyclopropenon mit β-Carbonyl-enolaten. I. Einsatz von Acetylaceton,Acetessigsäure-methylester, 2-Äthoxycarbonyl-cyclododecanon und Malonsäure-dimethylester

Reaction of Diphenylcyclopropenone with β-Carbonyl-enolates. I. Use of Acetylacetone, Methyl Acetoacetate, 2-Ethoxycarbonyl-cyclododecanone and Dimethyl Malonate The reaction of the sodium salts of acetylacetone ( 6 ), methyl acetoacetate (7) , 2-ethoxycarbonyl-cyclododecanone (8) , dimethyl malonate (19) and its methyl derivative 20 with diphenylcyclopropenone ( 5 ) in dimethylformamide at room temperature led to the unsaturated γ-lactones 14, 15, 17, 22 and 36 . In the case of dimethyl malonate ( 19 ), the halfester 21 , the acyl-malonic ester 24 and the indenone-malonic ester 23 were also isolated. Several intermediates and the final products were characterised by reactions and spectroscopically. A general mechanism is discussed for the addition of cyclo-propenones ( 1 ) to the enolate salts of β-dicarbonyl compounds 4 involving the bicyclic lactone-enolates 18 and 32 as intermediates. The products formed via 18 and 32 are considered to be the result of an attack of one of the oxygen atoms of the β-carbonyl-enolate anion ( 4 ), the product 24 , on the other hand, of the attack of the α-carbon atom of 4 ; in both cases the attack is on the carbonyl C-atom of 5 .     

Hydrate schwacher und starker Basen. XI. Die Kristallstrukturen von NaOH · 3,5H2O und NaOH · 7 H2O. Eine Präzisierung

Hydrates of Weak and Strong Bases. XI. The Crystal Structures of NaOH · 3,5H₂O and NaOH · 7 H₂O. A Refinement The crystal structures of the hydrates NaOH · 3,5 H₂O (space group P2₁/c, Z = 8 formula units per unit cell; lattice parameters: a = 6.481, b = 12.460, c = 11.681 Å, β = 104.12° at ?100°C) and NaOH · 7 H₂O (P2₁/c, Z = 4; a = 7.344, b = 16.356, c = 6.897 Å, β = 92.91° at ?150°C) have been redetermined using MoKα diffractometer data. The obtained refinement of the structures, including the localization also of the H atoms for the first time, has led to new findings with respect to the H bonds. In particular, in both hydrates there is one such interaction of the rare type OH^? …? OH₂, from an OH^? ion to an H₂O molecule, i. e. with the OH^? ion as the proton donor.     

Metall-Schwefelstickstoff-Verbindungen. 16. Reaktionsprodukte von Blei- und Zinnsalzen mit S4N4 Die Strukturen von PbN2S2 · NH3, PbN2S2 und SnCl4 · 2S4N4

Metal Sulfur Nitrogen Compounds. 16. Products of the Reaction of Lead- and Tin Salts with S₄N₄. Structures of PbN₂S₂ · NH₃, PbN₂S₂, and SnCl₄ · 2S₄N₄ PbN₂S₂ · NH₃ is monoclinic, P2₁/a, a = 5.671, b = 16.123, c = 6.102 Å, β = 95.12°, Z = 4, PbN₂S₂, however, orthorhombic, P2₁2₁2₁, a = 4.375, b = 7.654, c = 12.274 Å, Z = 4. The planar five-membered PbN₂S₂ rings in both compounds show no remarkable differences. In PbN₂S₂ · NH₃, the NH₃ molecule is bound to Pb perpendicularly to the plane of the ring. The structure of the long known addition compound SnCl₄ · 2S₄N₄ was determined. It is orthorhombic, Pc2₁b, a = 11.467, b = 11.995, c = 12.374 Å, Z = 4. Sn shows sixfold coordination, the two S₄N₄ rings are attached to Sn trans to each other via a N atom.     

α-Chlor-nitrone II: Eine Methode zur Darstellung von γ-Lactonen aus Olefinen. Über synthetische Methoden, 6. (vorläufige) Mitteilung

The addition products obtained by the Ag⁺-induced reaction of α-chloro-aldonitrones with olefins (see preceding communication) can be utilized efficiently for making γ-lactones (see scheme 1).