Inhibierungseffekt von 1,1,4,4-Tetraphenyl-2-tetrazen bei der radikalischen Polymerisation von Styrol

Ohne Zusammenfassung     

Synthesis of new azonia-helicenes with a quaternary nitrogen at the inner helix skeleton

The 16c-azonia[6]helicene salts, in which a carbon atom at the inner helix skeleton of [6]helicene is replaced by a quaternary nitrogen atom, have been synthesized by photo-induced intramolecular quater-nization of 2-[2-(1-chloronaphthyl)vinyl]benzo[h]quinolines in acetonitrile.     

Complexometric titration of calcium in the presence of larger amounts of magnesium

A simple and accurate titrimetric determination of calcium in the presence of larger amounts of magnesium is proposed. Calcium is extracted into a small volume of organic solvent as its glyoxal-bis(2-hydroxyanil) complex, and the calcium is titrated with EGTA. The end-point is sharp, and occurs when the red colour of the organic layer vanishes. This method has been successfully applied to the determination of calcium in sea-water with an error less than 0.1%.     

Calculation of membrane potential in synaptosomes with use of a lipophilic cation (tetraphenylphosphonium)

To estimate membrane potential in synaptosomes with the use of tetraphenylphosphonium (TPP+), an equation relating the amount of TPP+ accumulated in synaptosomes with membrane potential was derived from the following two assumptions. (1) TPP+ molecules were distributed into plasma membranes, mitochondria and cytosol of synaptosomes. (2) TPP+ achieves a Nernst equilibrium across both the synaptosomal and inner mitochondrial membranes. We propose three methods for calculation of membrane potential using this equation. The concentration of TPP+ was measured under various controlled conditions with an electrode selective for TPP+. The amount of TPP+ accumulated in synaptosomes was determined by measuring the difference between its initial concentration and the concentration after addition of synaptosomes, and membrane potential was estimated by the three methods. The resting potential of synaptosomes was estimated to be -75 to -90 mV by all of these methods. Membrane potentials under various controlled conditions were calculated, and the characteristics of the methods for estimation of membrane potential and those of membrane potential obtained by the methods are discussed.     

New resveratrol oligomers in the stem bark of Vatica pauciflora

Five new resveratrol oligomers; pauciflorols A-C (1-3), isovaticanols B (6) and C (8), and three new oligostilbene glucosides; pauciflorosides A (11), B (13), C (14), were isolated from the stem bark of Vatica pauciflora (Dipterocarpaceae) together with known 17 resveratrol oligomers (4, 5, 7, 9, 10, 12 and 15-25) and bergenin (26). The structures of isolates were established on the basis of detailed spectroscopic analysis. The typical and characteristic spectral properties of some resveratrol oligomers were also discussed.     

Novel chiral porphyrins with C2 symmetry

Described is the preparation of chiral octaethylporphyrin derivatives having two 2-substituted naphthyl groups in a trans orientation at the 5- and 15-meso positions and formyl or hydroxymethyl or alkoxymethyl group derived therefrom at the 10-meso position. One of the derivatives has been successfully resolved into enantiomers by means of HPLC.     

Reactivity and catalytic activity of cationic lonomers for the nucleophilic substitution reactions

Polystyrene-based crosslinked cationic ionomers containing ammonium or phosphonium chlorides (AxRCI and PxBuCI) were reacted with decyl methanesulfonate. The kinetic data were correlated with the swelling behavior of the ionomers and the solution viscosity of the corresponding linear ionomers. The reactivity of the ionomers was independent of the particle size of the ionomer beads, indicating no diffusion control of the reaction. The solvent and the ion content of the ionomers greatly affect the reactivity. In nonpolar solvents with a low acceptor number, A_N, such as toluene, the aggregation of ionic groups with an increasing ion content reduces the reactivity. A solvent with a high value of A_N, such as chloroform, led a very low reactivity independent of the ion content. Aprotic polar solvent, such as acetonitrila, promoted the dissociation of the ionic groups and furnished a relatively high reactivity independent of the ion content. Several catalytic substitution reactions were carried out under liquid-solid-solid triphase conditions. The kinetic results were accounted for in terms of slow nucleophile transport and fast chemical reaction within the ionomer particles. © 1994 John Wiley & Sons, Inc.