The determination of chlorinated biphenyls,chlorinated dibenzodioxins,and chlorinated dibenzofurans by GC-MS

High resolution gas chromatography, with mass selective detection, has been used for the analysis of PCB on methyl 50 % octyl polysiloxane (SB 50 Octyl), methyl octadecyl polysiloxane, and a smectic polysiloxane (SB Smectic); and for the analysis of polychlorodibenzodioxins and polychlorodibenzofurans with 1 to 8 chlorine substituents on 100 % cyanopropyl siloxane (SP 2331), smectic polysiloxane (SB Smectic), a new polar stationary phase (DB-Dioxin). The analysis has also been performed by column coupling.     

A new route to vinyltributyltin compounds by flash pyrolysis of alkyltributyltin acetates

Flash pyrolysis of alkyltributyltin acetates, at high temperatures (600–850° C) under a moderate vacuum provides a convenient route to vinyltin derivatives.     

Ion solvation in water clusters

We describe here molecular dynamics computer simulations performed to study the solvation of ions (Cl^? and Na⁺) in water clusters. Our simulations show that the calculated structure and dynamics of the clusters is very sensitive to the potential model which is used to describe the interactions. From the comparison with thermodynamic data and data from the photoelectron spectra we conclude that in Cl^?(H₂O)_n (n≤20) clusters the ion is located on the surface of the cluster.     

Identifizierung von sechs Komponenten des Spurpheromons der Ameisenart Lasius fuliginosus. Vorläufige Mitteilung

Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid are components of the trail pheromone of the ant species Lasius fuliginosus. The acids were extracted from the contents of the rectal ampullae and identified by the mass spectra and gas chromatographic retention times of the corresponding methyl esters.     

NMR parameters of the tetrahedrane [Fe2(CO)6(μ-SNH)], studied by experiment and DFT

The intramolecular dynamic behavior of the tetrahedrane-type cluster [Fe₂(CO)₆(μ-SNH)] 1 was studied by ¹³C NMR spectroscopy. The ⁵⁷Fe chemical shift of 1 and the coupling constants ¹ J(⁵⁷Fe,¹³C) were measured. These NMR parameters, and also ¹ J(⁵⁷Fe,¹⁵N), were found to be in good agreement with data calculated by using density functional theory (DFT) methods (B3LYP), based on the geometry calculated at the 6-311+G(d,p) level of theory. The isolobal replacement of the Fe(CO)₃ with BH fragments leads to the tetrahedranes [Fe(CO)₃(BH)(μ-SNH)] 2 and [(HB)₂(μ-SNH)] 3. Both were identified by calculations as minima on the respective potential energy surface (PES). However, the tetrahedrane-type structure of 3 is much higher in energy when compared with the planar cyclic isomers 3a and 3b.     

[1] Benzofuro [2,3-d] pyridazines II. Etude des benzofuropyridazones

The synthesis of 1,2-dihydro[1]benzofuro[2,3-d]pyridazin-1-one and 3,4-dihydro [1]benzofuro[2,3-d]pyridazin-4-one was accomplished by the eyclization of appropriately carbonyl-substituted benzofuran derivatives. Another successful synthetic route was provided using 1,2,3,4-tetrahydro[1]benzofuro[2,3-d]pyridazine-1,4 dione and 1,2,3,4-tetrahydro[1]benzofuro[2,3-d]pyridazin-4-one. The structure of a nitrobenzofuropyridazin-4-one was established using nmr and the nuclear Overhauser effect.     

Totalsynthese von natürlichem α-Tocopherol. 2. Mitteilung. Aufbau der Seitenkette aus (−)-(S)-3-Methyl-γ-butyrolacton

Total Synthesis of Natural α-Tocopherol A short and efficient route to optically pure (+)-(3 R, 7 R)-trimethyldodecanol ( 14 ) is demonstrated, 14 serving as side chain unit in the preparation of natural vitamin E. The synthesis of 14 is based on the concept of using a single optically active C₅-synthon of suitable configuration and functionalization to introduce both asymmetric centres in 14 . (?)-(S)-3-Methyl-γ-butyrolacton ( 1 ) and ethyl (?)-(S)-4-bromo-3-methylbutyrate ( 2 ), respectively, is used in a sequence of either two Grignard C,C-coupling reactions 5 → 8 and 12 → 13 or two Wittig reactions 17a → 18 and 20 → 21 to achieve this goal. 14 is converted to (2 R, 4′R, 8′R)-α-tocopherol (= vitamin E) by coupling with a chroman unit in known manner. Optical purity of products and intermediates is established.     

Naturstoffe aus Mikroorganismen. 8. Mitteilung [1]. Optimale Gewinnung von Proferrorosamin A aus Pseudomonas roseus fluorescens J. C. MARCHAL 1937

Optimum Obtention of Proferrorosamine A from Pseudomonas roseus fluorescens J. C. MARCHAL 1937. We have developed the best conditions for the culture of Pseudomonas roseus fluorescens, and a quantitative isolation of the Proferrorosamine A produced in the culture solution, in order to study the incorporation of 1-[¹⁴C]-glycerol in this propigment.     

Mechanical Stability Criterion, Triple-Phase Condition, and Pressure Differences of Matter Condensed in a Porous Matrix

In contrast to the triple-point condition of bulk material, condensed matter in porous media can coexist stably as liquid, solid, and vapor over a wide temperature range. The necessary conditions are found by a thermodynamic approach starting with the potential which reflects the grand canonical distribution and is characterized by heat and matter exchange. The other parameters are volume and surface. Therefore, it is designated the free mechanical potential. General expressions for mechanical stability are given. On condensation and melting the nonwetting phases vanish. These are thermodynamically stable phase transitions. For the opposing effects evaporation and fusion, an energy barrier must be transgressed either by nucleation or by intrusion as discussed here. These are metastable states. Phase transitions are the conditions which limit the triple-phase region. Within this region high negative pressures are generated in the unfrozen liquid independent of the pore size where it exists. The findings are applied to water in the disperse matrix of hardened cement paste. They are the basis for "micro ice lens pumping". Copyright 2001 Academic Press.