Application of the DSC analysis of thermoplastic polyurethane elastomers to a comparative study of their technological properties

The fusion and crystallization enthalpies, dynamic viscosity of melts and tensile properties of a series of commercially available thermoplastic polyurethane elastomers (TPU) were estimated. The DSC analysis has been proved as useful to prediction of the processability and tensile properties of TPU's with a similiar hard segment content.

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Zusammenfassung Schmelz- und Erstarrungsenthalpie, die dynamische Viskosität der Schmelze und Zugdehnungseigenschaften bei einer Reihe von im Handel erhältlichen thermoplastischen Polyurethanelastomere (TPU) wurden ermittelt. DSC-Anaiyse erwies sich als ein geeignetes Mittel zur Vorhersage der Verarbeitungsfähigkeit und der Zugdehnungseigenschaften von TPU mit ähnlichem Hartsegmentanteil.

     

Liquid chromatography of platinum metals and prospects of development

Summary A survey of the authors' work on liquid chromatography of platinum metals in the form of chelates with 1-(2-pyridylazo)-2-naphthol (PAN) is given. Extraction chromatography with PAN in isopentanol as a stationary phase was used to achieve a group concentration of these metals (Pd, Pt and Rh, concentration coefficient 100) from large volumes of aqueous solutions and a selective extraction of palladium from solutions containing other platinum, nonferrous and heavy metals on a 85–98° C thermostatted chromatographic column. The prospects for the use of liquid chromatography in the analysis of platinum metals are discussed.

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Flüssig-Chromatographie von Platinmetallen und zukünftige Entwicklungen

     

Synthesis of bidentate complexes of 3,6-dichloropicolinic acid

Bidentate complexes of the general formula M(C₆H₂Cl₂NO₂)₂ have been obtained from interaction of alcoholic solutions of Co, Ni, Mn, Mg, Mo, Zn, and Fe salts with aqueous solutions of 3, 6-dichloropicolinic acid. As appears in Russian original —Editor.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2327–2329, October, 1989.     

Rapid and sensitive silver-lipopolysaccharide staining using PhastSystem in fast horizontal polyacrylamide gel electrophoresis

A rapid and sensitive silver-lipopolysaccharide staining method has been developed by using PhastSystem. The total time of the procedure (including time of Phastgel electrophoresis) is within 2 h. It is at least 10 times faster than the previous reported methods and the sensitivity is also increased.     

Spectroscopic, thermal and electrochemical studies on some nickel(II) thiosemicarbazone complexes

Several complexes of thiosemicarbazone derivatives with Ni(II) have been prepared. Structural investigation of the ligands and their complexes has been made based on elemental analysis, magnetic moment, spectral (UV-Vis, i.r., (1)H NMR, ms), and thermal studies. The i.r. spectra suggest the bidentate mononegative and tridentate (neutral, mono-, and binegative) behavior of the ligands. Different stereochemistries were suggested for the isolated complexes. The thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used to study the thermal decomposition and kinetic parameters of some ligands and complexes using the Coats-Redfern and Horowitz-Metzger equations. The redox properties and stability of the complexes toward oxidation waves explored by cyclic voltammetry are related to the electron withdrawing or releasing ability of the substituent of thiosemicarbazone moiety. The samples displayed Ni(II)/Ni(I) couples irreversible waves associated with Ni(III)/Ni(II) process.     

Synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (1-oxa-2,7,8-triazaspiro[4,4]-2,8-dien-6-ones) via 1,3-dipolar cycloaddition and cycloelimination

An efficient and selective method for the synthesis of spiro-fused (C5)-isoxazolino-(C4)-pyrazolones (C) is reported. The process consists of utilizing the Baylis-Hillman reaction-or a quicker, stepwise MAC procedure-to give I followed by 1,3-dipolar cycloaddition and Swern oxidation to give beta-ketoesters H, which were condensed with hydrazine derivatives to provide hydrazones that underwent cycloelimination. These novel spiro-fused (C5)-isoxazolino-(C4)-pyrazolones were confirmed by spectroscopic analysis as well as single-crystal X-ray of 5. We also concluded that all condensations/cycloeliminations, except with hydrazine itself, were more effective with catalysts or higher reaction temperatures. For example, TiCl(4) was an efficient catalyst for hydrazone formation and cycloelimination with methylhydrazine, while phenyl-, benzyl-, and (4-methoxyphenyl)hydrazine reacted effectively without catalyst in refluxing xylene.     

Porphyrins with exocyclic rings. 14. Synthesis of tetraacenaphthoporphyrins, a new family of highly conjugated porphyrins with record-breaking long-wavelength electronic absorptions

The Soret band for porphyrins is usually observed in the near-ultraviolet at approximately 400 nm, and few examples of "nonexpanded" porphyrins with this major absorption band at values above 500 nm have previously been reported in the literature. Ring fusion with aromatic ring systems such as naphthalene, anthracene, or phenanthrene generally only produces minor bathochromic shifts to this diagnostic absorption band. In this paper, the synthesis of a series of tetraacenaphthoporphyrins and their metal chelates is reported. The compact nature of the acenaphthylene ring system allows the introduction of meso substituents using the Lindsey methodology. meso-Tetraphenylporphyrin 10a shows the presence of a Soret band at 556 nm, while p-methoxy and p-nitro substituents in 10f and 10g, respectively, further shift this band to 560 and 570 nm. Addition of TFA produces the corresponding dications with slightly higher wavelength Soret bands at 565, 573, and 588 nm. These values compare to 525 nm for the dication of tetraacenaphthylene 8, which lacks the meso-aryl substituents, indicating that steric crowding and its resulting distortion of the macrocyclic conformation is responsible for a significant albeit minor portion of these shifts. The nickel(II), copper(II), and zinc chelates of 10a produce Soret bands at 528, 545, and 558 nm, respectively, demonstrating that the trend for increasing red shifts in metalloporphyrins across the periodic table is retained for this series. The lead(II) chelate 19d gave an additional "hyper" shift that brought the Soret band to 604 nm. A similar red shift could be achieved by introducing four phenylethynyl substituents at the meso positions, and this highly conjugated porphyrin (20) also showed a Soret band at 604 nm, while the corresponding dication afforded this absorption band at 629 nm. The essentially additive "hyper" shift due to lead chelation brought the Soret band for the related lead(II) complex 22d to 642 nm. These effects are by far the largest ever observed for true porphyrins and demonstrate that the Soret band can be fined tuned to virtually any part of the visible spectrum.     

Crystal and molecular structures of the complexes of cobalt dichloride with 1-isopropenylimidazole and 1-vinylimidazole

The crystal and molecular structures of bis(1-isopropenylimidazole)dichlorocobalt (C₁₂H₁₆Cl₂·N₄Co) [R 0.036 (R _W 0.089) for 3229 unique reflections with I > 2σ(I)] and tetra(1-vinylimidazole)dichlorocobalt (C₂₀H₂₄Cl₂N₈Co) [R 0.031 (R _W 0.072) for 1863 unique reflections with I > 2σ(I)] were determined. In these molecular complexes, the monodentate terminal 1-alkenylimidazole ligands coordinate to the metal via a “pyridine” nitrogen atom. In C₁₂H₁₆Cl₂N₄Co, the Co atom has a distorted tetrahedral 2N,2Cl coordination. The coordination polyhedron of cobalt in C₂₀H₂₄Cl₂N₈Co is a strongly elongated 4N,2Cl octahedron. The Co-N and Co-Cl bonds [Co-N 2.015(2) and 2.032(4) Å; Co-Cl 2.229(2) Å] in the tetrahedral complex C₁₂H₁₆Cl₂N₄Co are shorter than those in the octahedral complex C₂₀H₂₄Cl₂N₈Co [Co-N 2.134(2) and 2.157(2) Å; Co-Cl 2.518(1) Å]. In the structures of both complexes there are short contacts involving the Cl atoms.     

Mobility of some ions produced by tritium betas

The aqueous solution of coumarin has been studied spectrophotometrically as a -ray dosimeter and effects of temperature and light conditions on the stability of response during post-irradiation storage have been studied. Post-irradiation storage at room temperature in dark showed that after a very small increase in absorbance within the first 6 d, the response of the dosimeter was stable up to 42 d. At lower temperature (–15 °C), there was some decrease in absorbance within the first 24 h followed by a stable response up to 35 d. For post-irradiation storage at higher temperatures (40, 60 °C) the dosimeter, apart from some initial increase in absorbance, showed a nearly stable response up to 25 d. The effect of different light conditions during post-irradiation storage has also been studied. When stored in fluorescent light the response was almost stable from 6 d till about 40 d. In diffuse sunlight, the response was stable up to about 35 d at 360 nm and 370 nm but showed a somewhat unstable behavior at 347 nm. The dosimetric solutions were unstable when exposed to direct sunlight.     

Benzolactams. 4. Reaction of 3',4'- or 4',5'-dialkoxy-substituted 1-(2'-Bromobenzyl)-2-ethoxycarbonyl-1,2,3,4-tetrahydroisoquinolines with alkyllithium. 1,2 and 1,4 additions of alkyllithium to benzolactams

Treatment of 1-(2'-bromo-3',4'-dialkoxybenzyl)-1,2,3, 4-tetrahydroisoquinoline carbamates, 1a,c, with excess alkyllithium gave 8-oxoberbines, 2a,c, which were successively attacked in situ with another molecule of alkyllithium to give 1,2 and/or 1,4 addition products. A primary alkyllithium, such as MeLi or BuLi, gave a 1,2 addition product, 8-methyleneberbine 9a or 8-butylideneberbine 3a. t-BuLi preferred 1,4 addition, followed by elimination of the alkoxy group, to give 9-tert-butyl-8-oxoberbine 6a or 7c. s-BuLi gave a mixture of 1,2 and 1,4 addition products, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3,4-tetrahydroisoquinoline 4a and 9-s-butyl-8-oxoberbine 5a. Similar treatments of carbamate 1b having no alkoxy group at its 3' position gave 1,2 addition products, 8-butylideneberbine 3b, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3, 4-tetrahydroisoquinoline 4b, and 1-(2'-pivaloylbenzyl)-1,2,3, 4-tetrahydroisoquinoline 6b, in all cases. Reactions of 1a with s-BuMgCl and isoPrMgCl also gave the 1,4 adduct, 5a, and its 9-isoPr analogue, 12a. Treatment of 9a with excess NaBH(4) in AcOH gave (+/-)-coralydine (10b).