On the Nature of Carbonyl Groups in Cellulosic Pulps

Apart from the reducing end groups, most celluloses contain small amounts of carbonyl groups in the mol/g range, which are introduced into the material by a variety of preparation, processing and purification steps. By a combination of carbonyl-selective fluorescence labeling (CCOA method) and UV resonance Raman spectroscopy it was demonstrated that carbonyls in celluloses are not only present as a C=O structure with an sp²-hybridized carbon, but also to a significant extent in sp³-hybridized form as hydrates or hemiacetals.     

A general, selective, high-yield N-demethylation procedure for tertiary amines by solid reagents in a convenient column chromatography-like setup

[reaction: see text] A traditional preparative chromatographic column can be used to achieve quantitative N-demethylation of tertiary N-methylamines and alkaloids. The filling is the crucial part and is loaded with different solid reagents in three reaction zones. The parent compound is charged on the column, and the neat N-demethylated secondary amine leaves the column some minutes later.     

Almost compact breathers in anharmonic lattices near the continuum limit

Certain strictly anharmonic one-dimensional lattices support discrete breathers over a macroscopic localized domain that in the continuum limit becomes exactly compact. The discrete breather tails decay at a double-exponential rate, so such systems can store energy locally, especially since discrete breathers appear to be stable for amplitudes below a sharp stability threshold. The effective width of other solutions broadens over time, but, under appropriate conditions, only after a positive waiting time. The continuum limit of a planar hexagonal lattice also supports a compact breather.     

A non-linear thermal wave in a reacting medium

Explicit examples are constructed of an impulsively initiated thermal wave in a reacting medium, with the volumetric heating and absorption being non-linear functions of the temperature-a typical situation in plasma physics. The different patterns of propagation exhibit, among other things, an unlimited outward motion, an extinction through shrinking within a finite time or an oscillatory motion. In addition it is also possible to generate a stationary thermal wave which has a finite width.     

Novel tocopheryl compounds XXIV. Studies into the nitrosation chemistry of γ-tocopherol: preparation of 5-nitroso-γ-tocopherol via an organomercury derivative of vitamin E

5-Nitroso-γ-tocopherol (5) was not accessible by direct nitrosation of γ-tocopherol (3), but was synthesized for the first time by nitrosation of an organomercurial intermediate (11) under aprotic conditions. Under protic conditions 5 exists in equilibrium with its ortho-quinone monoxime tautomer 6, the latter being the major component with >99%. NMR and analytical data of the tautomeric couple are reported for the first time. The chemistry of the nitrosation of γ-tocopherol was studied in detail. In the presence of oxygen, 5 is readily oxidized to 5-nitro-γ-tocopherol (7), whereas at elevated temperatures an additional process, the conversion of monoxime 6 into 5,6-tocopheryldione (8) under loss of hydroxylamine sets in. The experimental results agreed with the outcome of DFT computations.     

Luteapyrone,a Novel ƴ-Pyrone Isolated from the Filamentous Fungus Metapochonia lutea

In the process of screening for new bioactive microbial metabolites we found a novel ƴ-pyrone derivative for which we propose the trivial name luteapyrone, in a recently described microscopic filamentous fungus, Metapochonia lutea BiMM-F96/DF4. The compound was isolated from the culture extract of the fungus grown on modified yeast extract sucrose medium by means of flash chromatography followed by preparative HPLC. The chemical structure was elucidated by NMR and LC-MS. The new compound was found to be non-cytotoxic against three mammalian cell lines (HEK 263, KB-3.1 and Caco-2). Similarly, no antimicrobial activity was observed in tested microorganisms (gram positive and negative bacteria, yeast and fungi).     

Copolymerization of ethene with cyclic and other sterically hindered olefins

Sterically hindered olefins like norbornene, dimethanooctahydronaphthalene (DMON), 4‐methylpentene, and 3‐methylbutene can be copolymerised with ethene by metallocene/MAO catalysts. Different C₂‐, C_s‐ and C₁‐symmetric and meso‐zirconocenes were used. Only isolated and alternating norbornene sequences but no norbornene blocks are formed by substituted [Me₂C(Cp‐R)(Flu)]ZrCl₂ catalysts. The alternating microstructure leads to melting points up to 270°C for ethene‐norbornene copolymers and up to 380°C for the semi‐crystalline alternating copolymer of ethene and DMON. Other sterically hindered olefins such as 3‐methylpentene build more blocky structures with high glass transition temperatures. The mechanism for the insertion reaction of the different catalysts is discussed.