Zur thermodynamisch-phänomenologischen Beschreibung der Färbevorgänge I. Diskontinuierliches Modellsystem

The essential characteristics of a simple, discontinuous model system for mass transfer between two phases are discussed. It is shown that for dyeing processes that conform to this model it is possible, with the aid of the methods of non-equilibrium thermodynamics, to give an unambiguous definition of the concepts «rate of dyeing» and «affinity of dyeing», at any stage of dyeing. It is clear from the derived phenomenological equations that dyeing systems rarely reach a true equilibrium state (i.e. a stationary state of zero order), but that in general an osmotic or a DONNAN equilibrium is attained.     

Zur Kenntnis der metastabilen Übergänge in Massenspektren organischer Verbindungen

Observations in the mass spectra of several organic compounds indicate that metastable ions do not constitute conclusive evidence for one-step decomposition processes or elimination of structural entities. Contrary to accepted views it appears that metastable ions may arise from two-step or possibly even from multi-step fragmentation reactions.     

Fällung von Pentahalogenochromaten(III) aus wasserfreier Essigsäure

By adding alkali metal or ammonium acetate to solutions of Cr^III acetate in mixtures of acetic acid and acetyl halide, non-solvated alkali metal pentahalochromates(III), Cs₂(CrX₅), and acetic acid monosolvates of pentahalochromates(III) with nitrogen bases as a cation, i.e. (PyH)₂(CrX₅) · CH₃COOH, can be precipitated. Whilst the chlorochromate(III) ion shows a characteristic splitting of its ⁴A_2g—⁴T_2g absorption in acetic acid solution, which indicates C_4v symmetry, this splitting is not observed in all examined remission spectra of pentahalochromates(III) in the solid state. Their crystal structure should therefore be characterized by almost regular octahedral crystal fields of halogen around Cr³⁺ ions and probably by linked (CrX₆) units.     

Carbocyclen aus Monosacchariden. III. Zur Diastereoselektivität der Bildung von Cyclopentanderivaten. Umsetzungen in der Galactosereihe

Carbocycles from monosaccharides. III. Concerning the diastereoselective formation of cyclopentane derivatives. Transformations in the galactose series. The diastereoselectivity of the intramolecular nitrone-olefine cycloaddition of 1 , 3 and 4 (Scheme 1), yielding only 2 , 5 and 6 but none of the isomers 8 , 9 and 10 is explained by assuming a kinetic control and postulating that the relative activation energies of the two relevant transition states in the cyclization of e.g. 1 can be estimated from the conformers A and B , the latter being destabilized by a synperiplanar arrangement of the nitrone function and the 2-alkoxy-group (Scheme 2). It is further postulated, that this destabilization is responsible for the formation of (2,3)-trans configurated products. Since 2 , 5 and 6 are presumably thermodynamically more stable than 8 , 9 and 10 , a case was investigated, where the cycloaddition can either give thermodynamically less stable (2,3)-trans-product such as 12 or a thermodynamically more stable (2,3)-cis-product such as 13. 12 and 13 could both be formed from the aldehyde 25 via the nitrone 11 (Schemes 3 and 5). Treatment of the galactoside 16 first with Zn in aqueous butanol (forming among other products 25 and its 2-debenzyl-oxy-derivative) and then with N-Methyldroxylamine yielded the isoxazolidines 12 (72%), 13 (2%) and 27 (7%) (Schemes 4 and 6). Similarily, the anomeric silylated galactosides 17 and 23 gave 29 (78% from 17 , 77% from 23 ) and 27 (5% and 3%). Upon desilylation, 29 gave 32 , which was converted into 12 . The structure of the isoxazolidines was unambiguously deduced from their NMR. spectra and those of their derivatives 33 and 34 . Compound 32 was further transformed into its deoxyderivative 36 . The high diastereoselectivity of the cycloaddition restricts the number of diastereomeric, pentasubstituted cyclopentanes available by this method. However, cyclization of the 2-Hydroxy-aldehyde 37 (Scheme 8) gave the kinetically less favoured isomer 40 in a higher proportion, showing the differential influence of hydrogen-bonds on the relevant activation energies. Thermolysis of 32 gave 40 (79%) and 41 (11%). The structure of 41 was deduced from its NMR. spectra and those of its derivatives 42 and 43 . Thermolysis of 29 gave, after desilylation, 41 (42%), 40 (22%) and 32 (13%) and thermolysis of 6 lead to a 25 : 75 equilibrium with 44 (combined yield 90%). These transformations illustrate means leading to additional isomers and are in agreement with the proposed explanation of the diastereoselectivity in question.     

Zur Calorimetrie der Bismutoxidhalogenide. III Bismutoxidiodide

Calorimetry of Bismuth Oxidehalides. III. Bismuth Oxideiodide The heat of solution of all known solid phases in the system Bi₂O₃—Bil₃ in 4n HI were investigated. To compare the data they were converted to the standardized formula Bi₂O_3?y/2I_y with 0 ≤ Y ≤ 2. The data see “Inhaltsübersicht”.