Die chemische Zersetzung von Seltenerd-Nitraten: Eine neue Methode zur Anreicherung schwerer Yttererdnitrate im kg-Maßstab

Summary On addition of oxidizable organic substances to molten rare earth nitrates reaction takes place with evolution of nitric oxides and formation of basic nitrates, the two-step hydrolysis of which results in effective enrichment of heavy yttrium earths (YE) from rare earth mixtures in kg-quantities. Using methanol as reducing agent the reaction takes place at 160°C, much lower than using the method of purely thermal decomposition. In both methods after the first hydrolysis step a productYE(OH)_1.5(NO₃)_1.5·H₂O can be isolated.

     

Photochemical Reactions 151st Communication. Photo-oxygenation of (E)- and (Z)-7-Methyl-β-ionone

Photo-oxygenation of (E)-7-methyl-β-ionone ((E)? 1 ) and (E)-8-methyl-β-ionone ((E)? 2 ) gave rise to the formation of the hydroperoxy-enones (E)? 10 and (E)? 15 , respectively, which, in part, underwent intramolecular epoxidation to the hydroxy-epoxy-ketones 11 and 16 , respectively, The product distribution of the photo-oxidation of (Z)? 1 shows a marked influence of the skewed ground-state conformation of the dienone chromophore. Thus, singlet oxygen (¹O₂) was added to C(γ) of the dienone chromophore leading to the spirocyclic peroxy-hemiacetal 12 and to the endoperoxide 13 . In addition, the tricyclic peroxide 14 was formed as a new type of product via primary addition of ¹O₂ to C(γ) of the dienone chromophore. The structure of 14 was established by X-ray crystal-structure analysis of the hemiacetal 22 .     

The dependence of 13C-1H coupling constants on CCC bond angles

The relationship between one-bond ¹³C-¹H coupling constants and internuclear CCC bond angles (_n) in hydrocarbons of the type R₂CH₂ is best approximated by a quadratic expression.     

An experimental and theoretical study of surface segregation in a Fe-6at.%Si bicrystal

The analysis of segregation phenomena in bicrystals is an important step for the understanding of combined effects of the elementary diffusion processes involved in the segregation in polycristalline systems. The segregation of Si and P in a Fe-6at.%Si bicrystal with a (100) and (110) surface has been investigated by means of AES (Auger electron spectroscopy). For these experiments the technique of a linearly increased temperature has been applied. Significant differences between the segregation kinetics at the two surfaces of the sample have been found on the one hand for the maximum coverage of P and on the other hand for the high temperature behaviour of Si. Additionally, model calculations based on the KTBIM (kinetic tight binding Ising model) have been performed to qualitatively describe the experimental results. It is shown, that the striking differences between the segregation behaviour at the two differently oriented surfaces can be explained by different segregation energies of P, whereas Si plays a minor role due to its relatively small segregation energy.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Darstellung,Mössbauer- und Schwingungsspektren der Komplexe [SnCl4F]⊖, [SnCl4(NCS)]⊖ und [SnCl4(NCS)2]2⊖

Preparation, Mössbauer and Vibrational Spectra of the Complexes [SnCl₄F]^?, [SnCl₄(NCS)]^?, and [SnCl₄(NCS)₂]^2? N(CH₂)₄F and N(CH₂)₄SCN react in liquid SO₂ with SnCl₄ yielding the adducts [N(CH₃)₄][SnCl₄F] (I), [N(CH₃)₄][SnCl₄(NCS)] (II) and [N(CH₃)₄]₂[SnCl₄(NCS)₂] (III).respectively. Mössbauer and vibrational spectra indicate for the anion of I a fluoro-bridged species, which is probably tetrameric like the isoelectronic SbCl₄F. For II dimeric moieties are proposed with bridging S-atoms, while [SnCl₄(NCS)₂]^2? has an octahedral structure with N-bonded isothiocyanate groups in the trans-positions.     

Column chromatographic prefractionation leads to the detection of 543 different gene products in human fetal brain

In a previous publication a large series of proteins were identified in fetal human brain by the use of two-dimensional electrophoresis (2-DE) with subsequent matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and MALDI-tandem time-of-flight (TOF/TOF) analysis. Further identification of many more different spots by traditional 2-DE without additional step such as narrow immobilized ph gradient (IPG) strips or prefractionation seems unlikely and we therefore decided to separate extracted brain proteins by ion-exchange chromatography using a TSK gel DEAE-5PW column followed by 2-DE of individual fractions and analysis by MALDI-TOF/TOF with LIFT technology in fetal brain of the early second trimester. About 1880 protein spots corresponding to 543 different gene products were identified. These proteins included housekeeping, signaling, cytoskeletal, metabolic, antioxidant, and neuron/synaptosomal specific proteins. Among these, 314 gene products (314/543, 57.8%), which have never been detected in traditional 2-DE of human fetal brain, were observed by this method. This updated map of fetal brain proteins may serve as data base and reference map for fetal brain proteins, and the methodology applied may be used as a valuable analytical tool for the basis of protein expressional studies in health and disease.     

CHARACTERIZATION OF A MICROSECOND INTERMEDIATE IN THE LASER FLASH PHOTOLYSIS OF SMALL PHYTOCHROME FROM OAT

Abstract— Irradiation of small phytochrome from oat in its P_r form with 15 ns laser pulses of different wavelengths(605–655 nm) gave rise to a difference absorption with maxima at 400 and 685 nm for the first detectable transient. Bleaching of a 660 nm band was observed, non-recuperable up to 1 ms. The transient absorption has a lifetime of 70±15 μs at 273 K. The transient is tentatively identified as lumi-R and the conformation of its chromophore is postulated to be more extended than that of P_r. A deviation from the exponential decay of the lumi-R absorption at 284 and 300 K and the lack of observable enhancement of the far-red absorption within 1 ms are interpreted in terms of the appearance of still other intermediates on this time scale between lumi-R and P_fr phytochrome.     

A Flexible Stereoselective Synthesis of the Spirosesquiterpenes (±)-β-Acorenol, (±)-β-Acoradiene, (±)-Acorenone-B and (±)-Acorenone via an Intramolecular Ene-Reaction

The racemic spirosesquiterpenes β-acorenol ( 1 ), β-acoradiene ( 2 ), acorenone-B ( 3 ) and acorenone ( 4 ) (Scheme 2) have been synthesized in a simple, flexible and highly stereoselective manner from the ester 5 . The key step (Schemes 3 and 4), an intramolecular thermal ene reaction of the 1,6-diene 6 , proceeded with 100% endo-selectivity to give the separable and interconvertible epimers 7a and 7b . Transformation of the ‘trans’-ester 7a to (±)- 1 and (±)- 2 via the enone 9 (Scheme 5) involved either a thermal retro-ene reaction 10 → 12 or, alternatively, an acid-catalysed elimination 11 → 13 + 14 followed by conversion to the 2-propanols 16 and 17 and their reduction with sodium in ammonia into 1 which was then dehydrated to 2 . The conversion of the ‘cis’-ester 7b to either 3 (Scheme 6) or 4 (Scheme 7) was accomplished by transforming firstly the carbethoxy group to an isopropyl group via 7b → 18 → 19 → 20 , oxidation of 20 to 21 , then alkylative 1,2-enone transposition 21 → 22 → 23 → 3 . By regioselective hydroboration and oxidation, the same precursor 20 gave a single ketone 25 which was subjected to the regioselective sulfenylation-alkylation-desulfenylation sequence 25 → 26 → 27 → 4 .     

29Si-NMR-Untersuchungen an einigen Cyclosilanderivaten

²⁹Si-NMR spectras of some new cyclosilane derivatives were measured. First aspects of the dependence of chemical shift on ring size and kind of substituents are given.