Preparation and Crystal Structure of MnBiS<Subscript>2</Subscript>Br

Summary. Black single crystals of MnBiS₂Br were obtained by the reaction of stoichiometric amounts of α-MnS, Bi, S, and BiBr₃ (3:2:3:1) at 600°C for 4 weeks. The compound crystallises in the monoclinic system, space group C2/m, with a = 12.767(2), b = 3.9468(4), c = 9.574(1) ?, β = 90.87(2)°, and Z = 4. The crystal structure refinement based on 720 reflections converged at R = 0.0244 and wR2 = 0.0579, respectively. MnBiS₂Br forms a layer structure consisting of MnS₆ octahedra, MnS₂Br₄ octahedra, and BiS₃₊₂ pyramids.     

Arbitrary torsion classes and almost free abelian groups

Using the set theoretical principle ? for arbitrary large cardinals κ, arbitrary large strongly κ-free abelian groupsA are constructed such that Hom(A, G)={0} for all cotorsion-free groupsG with |G|<κ. This result will be applied to the theory of arbitrary torsion classes for Mod-Z. It allows one, in particular, to prove that the classF of cotorsion-free abelian groups is not cogenerated by aset of abelian groups. This answers a conjecture of Göbel and Wald positively. Furthermore, arbitrary many torsion classes for Mod-Z can be constructed which are not generated or not cogenerated by single abelian groups.     

Epimeric Isopavine N-Oxides from Roemeria refracta

Roemeria refracta DC. (Papaveraceae) of Turkish origin yielded two novel epimeric N-oxides, (?)-(5R, 11S,14R)-reframidine N-oxide ( = (?)-(5R, 11S,14R)-11,12-dihydro-14-methyl-11,5-(iminomethano)-5H -cyclohepta[1, 2-f: 4, 5-f′]bis[1,3]benzodioxole 14-oxide; 1 ) and (?)-(5R, 11S, 14S)-reframidine N-oxide ( = (?)-(5R, 11S, 14S)-11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxole 14-oxide; 2 ). The isolated (?)-roelactamine ( = (?)-11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-one, 4 ) is the first natural isopavinoid incorporating a lactam group. The epimeric (?)-15-(2-oxopropyl)reframidines ( = (?)-1-[11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-y1]propan-2-ones; 5/6 ) and the epimeric (?)-ethyl (reframidin-15-yl)acetates ( = (?)-ethyl [11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-y1]acetates; 7/8 ) are probably artifacts. (±)-Coclaurine ( 9 ), (±)-N-methylcoclaurine ( 10 ), (?)-roemeridine ( 11 ), and N-feruloyltyramine ( 12 ) are also isolated from R. refracta together with the previously reported bases. Specific ¹³C-NMR assignments are reported for the first time for the isopavines.     

Synthese von N-(4-Aminobutyl)-16-aza-19-nonadecanlactam und N-(4-Aminobutyl)-17-aza-20-icosanlactam (Desoxoinandenin)

Synthesis of N-(4-Aminobutyl)-16-aza-19-nonadecanelactam and N-(4-Aminobutyl)-17-aza-20-icosanelactam (Desoxoinandenine) According to Scheme 1, the two homologous macrocyclic spermidine derivatives 12 and 23 were synthesized. Key steps in both cases were two different types of ring-enlargement reactions. Compound 12 was identical with a degradation product of the naturally occurring spermidine alkaloids of inandenine-type.     

Cascade of coil-globule conformational transitions of single flexible polyelectrolyte molecules in poor solvent

We show that hydrophobic flexible polyelectrolyte molecules of poly(2-vinylpyridine) and poly(methacryloyloxyethyl dimethylbenzylammonium chloride) are trapped and frozen due to adsorption on the mica surface, and the observed AFM single molecule structures reflect the molecular conformation in solution. An increase of the ionic strength of the solution induces the cascade of abrupt conformational transitions due to the intrachain segregation from elongated coil to compact globule conformations through intermediate pearl necklace-globule conformations with different amounts of beads per chain. The length of the necklaces and the number of beads decrease, while the diameter of beads increases with the increase of ionic strength. Coexistence at the same time of extended coils, necklaces with different amounts of beads, and compact globules indicates the cascade of the first-order-type phase transitions.     

Single flexible hydrophobic polyelectrolyte molecules adsorbed on solid substrate: transition between a stretched chain, necklace-like conformation and a globule

Single flexible polyelectrolyte molecules of poly(2-vinylpyridine) undergo conformational transition from a stretched wormlike coil to a necklace-like globule, and to a compact globule depending on pH and ionic strength in aqueous solution in good agreement with recent theoretical reports. AFM investigations allow the visualization of details of the chain conformation on mica and the extraction of quantitative statistics of molecular dimensions.     

Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds. XII-pentafluorophenyl derivatives af phosphorus (V) halides

The Mass spectral fragmentation processes for a number of alkyl and aryl subtituted phosphinyl and phosphonyllk halides and their thio analogs are discussed with respect to two intramolecular rearrangment processes. The first is aryl fluorine transfer to phosphorus and the second concerns a rearrangement depicted as follows, i.e. a reverse Arbuzov reaction RR′XP?S→RXP? S? R′. Both pathways are supported by evidence obtained form metastable ions and mass analyzed ion kinentic energay spectra. The previously observed phenomenon of subtituent coupling is also describedc where ita occurs in the phosphinyl compounds. The mass spectra of a number of mixed fluoro-pebtafkuorophenyl phosphorances are also discussed.     

Subalgebras that are cyclic as submodules

Let R be an associative, commutative, unital ring. By a R-algebra we mean a unital R-module A together with a R-module homomorphism : _R ⁿ AA (n2). We raise the question whether such an algebra possesses either an idempotent or a nilpotent element. In section 1 an affirmative answer is obtained in case R=k is an algebraically closed field and dim_kA<, as well as in case R=, dimS<, and n0(2). Section 2 deals with the case of reduced rings R and R-algebras which are finitely generated and projective as R-modules. In section 3 we show that the generic algebra over an integral domain D fails to have nilpotent elements in any integral domain extending its base ring D_n,m, and thus acquires an idempotent element in some integral domain extending D_n,m.Partially supported by National Science Foundation Grant GP-38229.