Thermal properties and solubility of ordered aromatic polyamides containing a methyl-substituted phenylene linkage

Ordered aromatic polyamides and copolyamides were prepared by the polycondensation of terephthaloyl and isophthaloyl dichlorides with symmetrical diamines containing preformed amide linkages derived from unsymmetrical methyl—substituted aromatic diamines at low temperature. Thermal properties and solubilities of the ordered polyamides were compared with those of the corresponding random polyamides. There was little difference between thermal stabilities of the ordered polyamide and the corresponding random one, while the former was less soluble in organic solvents than the latter, depending on the extent of hydrogen bonding of the amide groups. The thermal stability of the alternating copolyamides containing both terephthaloyl and isophthaloyl groups as acid components was less than that of the corresponding homopolymers having either a terephthaloyl or an isophthaloyl group, and the solubility of the former resembled that of the corresponding ordered homopolysiophthalamides in accord with the extent of hydrogen bonding of the amide groups in both polymers.     

Interference from electrostatic charges in the microdetermination of halogen and sulphur by the combustion method

Summary In the analysis of halogen and sulphur by the combustion method employing silver granules, electrostatic charges on the absorption funnel has been experimentally shown to cause inaccurate weighing of the funnel.An investigation of the influence of this phenomenon on blank values has been made, and possible countermeasures have been examined. By cooling the heated funnel in a desiccator saturated with moist air, the charges are removed and satisfactory analyses are obtained.

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Zusammenfassung Bei der analytischen Bestimmung der Halogene und des Schwefels durch Verbrennung und Bindung an Silbergranellen verursachen, wie gezeigt werden konnte, elektrostatische Aufladungen der Absorptionsgefäße Wägefehler. Untersuchungen über den Einfluß dieser Erscheinung durch Bestimmung von Leerwerten wurden ausgeführt und die Möglichkeit von Gegenmaßnahmen geprüft. Durch Abkühlen der heißen Absorptionsgefäße in einem mit feuchter Luft gefüllten Exsiccator lassen sich die Aufladungen beheben und richtige Analysenergebnisse erzielen.

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Résumé On a montré expérimentalement que dans l'analyse des halogènes et du soufre suivant la méthode de combustion avec granules d'argent, les charges électrostatiques sur le tube d'absorption étaient la cause d'une pesée inexacte de ce tube.On a fait une étude de l'influence de ce phénomène sur les valeurs à blanc et l'on a examiné la possibilité de mesures de l'éviter. En refroidissant le tube chauffé dans un dessicateur saturé d'air humide, on élimine les charges et l'on obtient des analyses satisfaisantes.

     

Improvements in the microdetermination of chlorine and bromine in organic compounds

Summary Schöniger's method for the microdetermination of halogen has been improved by using ammonium hydroxide solution as an absorbing solution instead of sodium hydroxide solution in order to simplify the after treatment. On boiling the absorbing solution, interfering ions can be removed together with excess ammonia. Ammonium halide which formes in the solution is titrated with AgNO₃ solution in the presence of an adsorption indicator. Satisfactory results are obtained more rapidly.

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Zusammenfassung Um die Weiterbehandlung der Absorptionslösung bei der Mikrobestimmung der Halogene nachSchöniger zu vereinfachen, wurde an Stelle von Natronlauge Ammoniaklösung verwendet. Durch Kochen der Absorptionslösung können störende Ionen zugleich mit dem Ammoniaküberschuß entfernt werden. Das in der Lösung entstandene Ammoniumhalogenid wird mit Silbernitrat in Gegenwart eines Adsorptionsindikators titriert. Bei verkürzter Analysendauer werden zufriedenstellende Ergebnisse erzielt.

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Résumé On a amélioré la méthode deSchöniger pour le microdosage des halogénes en utilisant une solution d'ammoniaque comme absorbant à la place de la solution d'hydroxyde de sodium afin de simplifier le traitement ultérieur. En faisant bouillir la solution d'absorption on peut éliminer les ions gênants avec de l'ammoniaque en excés. On titre l'halogénure d'ammonium qui se forme en solution, par une solution d'AgNO₃ en présence d'un indicateur d'adsorption. On a obtenu des résultats satisfaisants plus rapidement.

     

NAD/NADH models with axial/central chiralities: superiority of the quinoline ring system

Precursors of NAD model compounds 1c and 3a,b were successfully resolved into their atropisomers with respect to carbamoyl rotation. Atropisomers of quinoline derivatives are much more stable than pyridine derivatives as determined by cyclic voltammetry and X-ray crystallography. The 1,4-reduction of NAD model compound 4 was successfully achieved, affording novel NADH model compound 5. The rotational properties of the side chain of 5 were investigated by means of dynamic NMR. The rotational rate and syn/anti ratio, which indicate the orientation between carbonyl oxygen and hydrogen at the 4-position, are significantly affected by addition of magnesium ion. In the rotational transition state, the double-bond character of the C(carbonyl)-N(amide) bond is disrupted judging from the activation parameters. The oxidation of chiral 5 with p-benzoquinone in the presence of magnesium ion catalyst gave predominantly one enantiomer of 4. On the other hand, oxidation of 5 with p-chloranil (tetrachloro-p-benzoquinone) in the absence of magnesium ions affords the opposite enantiomer of 4 as the major product. The product enantiomer ratio is parallel to the syn/anti ratio in the starting material, indicating the importance of ground state conformation to stereochemistry of the reaction.     

Metabolic fate of [14C]triglyceride-entrapped lactosylceramide-bearing liposomes after intravenous injection into mouse.

We investigated the distribution and fate of liposomes after their intravenous injection into a mouse. Liposomes were composed of dimyristoylphosphatidylcholine, cholesterol and dicetylphosphate (7:2:1, molar ratio) with or without lactosylceramide. They were characterized as small unilamellar vesicles, approximately 100 nm in diameter, using gel-exclusion chromatography on a Sephacryl S-1000, freeze-fracture electron microscope and dynamic light scattering method. Liposomes were very stable in serum as seen by the results of leakage of the entrapped marker and electrophoresis experiments. We demonstrated that liposomes were internalized by way of an endocytotic process via coated vesicles detected in the electron microscope. The increase in liver uptake of lactosylceramide-bearing liposomes was mostly accounted for by enhanced uptake in the parenchymal cells, while uptake by non-parenchymal cells was only slightly increased. This observation supported the notion that a galactose-specific receptor was involved in liver uptake of lactosylceramide liposomes. The lactosylceramide-bearing liposomes were preferentially recovered in the liver and were found to first be predominantly localized in the mitochondria-lysosomal fraction. They were then decomposed by lysosomal enzymes, and the hydrolyzed components were reincorporated into membrane phospholipids in the microsomal fraction. At the same time, a rapid and reversible exchange of phosphatidylcholine between microsomes and mitochondria was demonstrated.     

Deoxygenation of sugar trifluoromethanesulfonates by sodium metal in liquid ammonia and by photolysis

Several trifluoromethanesulfonyl(TFMS) derivatives of sugars were prepared and treated with sodium in liquid ammonia or subjected to ultraviolet irradiation. Three 3-$\text{O}$-TFMS derivatives gave the corresponding 3-deoxy compounds, but a 2-$\text{O}$-TFMS derivative gave a branched-chain sugar.     

Tandem five membered-ring selective Prins reaction and Friedel–Crafts reaction

A tandem reaction consisting of five membered-ring selective Prins cyclization and subsequent Friedel–Crafts cyclization was developed. The reactions of phenyl homoallylic alcohol 3 and benzaldehyde derivatives 6 afforded tetrahydroindenofurans 7 or pentacyclic products 8, depending upon the quantity of 6. Also homoallylic alcohol 12 having an alkyne–cobalt moiety reacted with 6 to give rise to tetrahydroindenofurans 13 in good yields.     

Skin friction reduction by large air bubbles in a horizontal channel flow

Microbubble and air film methods are believed to be applicable to skin friction reduction in ships. Small bubbles are dispersed into the turbulent boundary layer in the former case, and wide air layers cover the wall surface in the latter case. Previous studies did not specifically address the intermediate case between the microbubble and air film conditions. This study is concerned with the possibility and mechanism of drag reduction using relatively large air bubbles compared to the boundary layer thickness in a horizontal turbulent channel flow. The relationship between local skin friction and the bubble’s interfacial structure is investigated by synchronizing the measurement of wall-shear stress with the image acquisition of bubbles. The bubble sizes range from 2 to 90 mm approximately. As a result, a negative correlation between the local skin friction and the local void fraction is confirmed by the time-resolved measurement. A new observation is the fact that the local skin friction decreases drastically in the rear part of individual large bubbles, and rapidly increases after the bubble’s rear interface passes. This characteristic underlies the bubble-size dependency of the average skin friction in the intermediate bubble size condition.     

Determination of 1-nitropyrene metabolites by high-performance liquid chromatography with chemiluminescence detection

Three metabolites of 1-nitropyrene, i.e., 3-hydoxy-1-nitropyrene (3-OHNP), 6-hydoxy-1-nitropyrene (6-OHNP) and 8-hydoxy-1-nitropyrene (8-OHNP), were sensitively and selectively detected by HPLC with peroxyoxalate chemiluminescence (CL) detection. In the system, the three OHNPs were reduced to their corresponding amino derivatives through a reduction column packed with Pt/Rh-coated alumina and then concentrated on a concentrator column. By rotating a switching valve, the analytes were eluted into a separator column (ODS), separated and then detected by the bis(2,4,6-trichlorphenyl)oxalate-H(2)O(2) CL system. The detection limits (signal-to-noise ratio=3) were in the range from 5fmol (6-OHNP and 8-OHNP) to 12fmol (3-OHNP) per injection. To demonstrate the proposed method, it was used to determine three compounds in the incubation mixture of 1-nitropyrene and rat S9 mix.