The cleavage of heterocyclic compounds in organic synthesis II Use of 5‐nitroisatine for synthesis of various nitrogenous heterocycles

The reactions of 5‐nitroisatine were studied with nucleophiles like heterocyclic amines and alkaline hydroxide. With the use of alkaline hydroxide it was converted into 2‐amino‐5‐nitrophenylglyoxylic acid 2 , with piperidine, morpholine and carbethoxypiperazine to its amides 4a‐4c or by oxidation to 5‐nitroanthranilic acid 7. This acid was used for synthesis of 3‐hydroxy‐6‐nitro‐2‐phenyl‐1H‐quinolin‐4‐one 10. Semicarbazone of 5‐nitroisatine 11 was converted to 5‐(2‐amino‐5‐nitrophenyl)‐2,3,4,5‐tetrahydro‐1,2,4‐triazine‐3,5‐dione 12. Cyclocondensation of this compound to afford 8‐nitro‐2,3‐dihydro‐5H‐[1,2,4]triazino‐[5,6‐b]indol‐3‐one 13 was unsuccessful.     

Structure and mechanical properties of poly(l-lactide)/layered silicate nanocomposites

Poly(ε-caprolactone) (PCL) masterbatches with the intercalated and the exfoliated morphology were prepared by ring opening polymerization of ε-caprolactone in the presence of organomodified montmorillonite (MMT) Cloisite 30B. Poly(l-lactide) (PLLA) nanocomposites with Cloisite 30B or PCL masterbatches were prepared by melt blending. The effects of the silicate type, MMT content and the nanocomposite morphology on thermal and mechanical properties of PLLA nanocomposites were examined. The montmorillonite particles in PLLA/Cloisite 30B and PLLA/intercalated masterbatch nanocomposites were intercalated. In contrary to expectations, the exfoliated silicate layers of exfoliated masterbatch were not transferred into the PLLA matrix. Due to a low miscibility of PCL and PLLA, MMT remained in the phase-separated masterbatch domains. The stress-strain characteristics of PLLA nanocomposites, Young modulus E, yield stress σ_y and yield strain ε_y, decreased with increasing MMT concentration, which is associated with the increase in PCL content. The expected stiffening effect of MMT was low due to a low aspect ratio of its particles and was obscured by both plastifying effects of PCL and low PLLA crystallinity. Interestingly, in contrast to the neat PLLA, ductility was enhanced in all PLLA/Cloisite 30B materials and in PLLA/masterbatch nanocomposites with low MMT concentrations.     

Kalorimetrische untersuchung von binären legierungen des platins und palladiums mit gallium,indium und thallium

Employing tin and lead solution calorimetry, the formation enthalpies of those phases having platinum and palladium as major component have been determined in the PdGa, PdIn, PdTl, PtGa und PtIn systems. These enthalpies are highly exothermic and suggest strong atomic interaction betweens palladium and platinum on the one hand and the third subgroup elements on the other. The experimental values have been compared with those obtained from the Miedema model. The thermodynamic data are discussed and related to the crystal structures found with these alloys.     

Syntheses and PE-Spectroscopic Investigations of 2,6- and 3,5-Bridged 1,4-Dimethylidenecyclohexanes

Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 .     

Biocompatible hydrogels based on chitosan,cellulose/starch,PVA and PEDOT:PSS with high flexibility and high mechanical strength

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break?>?300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings.

Graphical abstract

     

Photometrische Wismutbestimmung mit Brenzcatechinviolett

Zusammenfassung Es wurden die Bedingungen der photometrischen Wismutbestimmung mit Brenzcatechinviolett bei der WellenlÄnge _max=580 nm ausgearbeitet und der Einflu\ der Fremdionen untersucht. Das Lambert-Beersche Gesetz gilt in den Konzentrationsgrenzen 0,0–6,2 g Bi/ml bei 1,6 cm Schichtdicke.

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Summary A method is given for the photometric determination of bismuth using pyrocatechol violet, at the wave-length of _max=580 nm. Interferences by foreign ions have been examined. Beer's law is obeyed from 0.0 to 6.2 g Bi/ml (1,6 cm cuvettes).

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Als erste Mitteilung dieser Reihe soll die Arbeit: Malát, M.: Naturwissenschaften 48, 569 (1961) betrachtet werden.     

Modelling,optimisation and control of selectivity in the separation of aromatic bases by electrokinetic chromatography using a neutral cyclodextrin as a pseudostationary phase

A simple mathematical model describing the separation of a series of aromatic bases by electrokinetic chromatography using beta-cyclodextrin (beta-CD) as a pseudostationary phase is described. The model takes into account changes in electrolyte pH and the different formation constants between the neutral and charged forms of the analytes with the CD. Constants in the model were obtained within the two-dimensional experimental space defined by pH and [beta-CD] with nonlinear regression using only five experimental points. These constants agreed with expected trends in analyte-CD interactions and predicted much higher formation constants for the neutral analyte-CD complex than for the charged analyte-CD complex. Correlation between predicted and observed mobilities using additional 20 points within the experimental space gave r(2) = 0.995. Optimisation of the pH and [beta-CD] was performed using both the normalised resolution product and minimum resolution product criteria and provided two optimum separations which exhibited different selectivities. Differences between predicted and observed migration times at these optima were less than 2.5 and 5% for the normalised resolution product and the minimum resolution criteria, respectively. In both cases the correct migration order was predicted. The model was also applied successfully to the optimisation of conditions for the separation of a specific mixture of analytes or for conditions under which particular analytes migrated in a desired order.     

Moisturizing emulsion systems based on the novel long-chain alkyl polyglucoside emulsifier

Mesomorphic behavior of the novel long-chain alkyl polyglucoside emulsifier comprising arachidyl alcohol (C₂₀), behenyl alcohol (C₂₂), and arachidyl glucoside was investigated in order to determine the prevalent stabilization mechanism and moisturizing capacity of emulsion systems based on it. For this to be accomplished thermoanalytical methods (differential scanning calorimetry and thermogravimetric analysis) coupled with microscopy, rheological, X-ray diffraction methods and a short-term in vivo study of skin hydration level were performed. Obtained results have proved that C₂₀/C₂₂ alkyl polyglucoside mixed emulsifier is able to provide the synergism between the two main types of lamellar phases, the liquid-crystalline (Lα), and the gel crystalline (Lβ) one, building the emulsion systems of different stability and performance. Formation of lamellar structures influenced for more than one half of water within the system to be entrapped. Conducted investigation of hydration potential in real-time conditions provided valuable information on the investigated emulsion vehicles’ moisturizing potential as well as their contribution to the skin barrier improvement. Therefore, it could be expected that emulsions based on this alkyl polyglucoside emulsifier could influence the delivery of active ingredients of both the lipophilic and hydrophilic type. The employment of thermoanalytical methods in our work suggests the possibility for thermal methods to be used more frequently in the characterization of both the novel raw materials and the belonging emulsion systems.     

Photoinduced phase transitions and helix untwisting in the SmC* phase of a novel cinnamoyl-based liquid crystal

A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation P _s was measured and it was found that UV irradiation induces a decrease in the values of P _s. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases.