Synthesen von Heterocyclen, 111. Mitt.: Zur Umsetzung von Benzoylaceton und seinen Derivaten mit Malonylchlorid

Zusammenfassung Der Vorgang der thermischen Umlagerung des 4-Hydroxy-5-acetyl-6-phenyl-pyrons-(2) (1) zum 4-Hydroxy-5-benzoyl-6-methyl-pyron-(2) (4) wird an Hand weiterer Beispiele studiert und ferner der Einfluß der Substituenten am C-5 bzw. C-6 des Lactonringes untersucht.

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An investigation of more examples of the thermal rearrangement of 5-acetyl-4-hydroxy-6-phenyl-pyrone-(2) to 5-benzoyl-4-hydroxy-6-methyl-pyrone-(2) was carried out, it showed the influence of substituents at C-5 and C-6 of the lactone ring.

     

Determination of copper in medicinal plants used as dietary supplements by atomic absorption spectrometry with direct flame solid analysis

An alternative device for the direct solid analysis (DSA) for copper determination by flame atomic absorption spectrometry (FAAS) is proposed. Copper was directly determined in commercial medicinal plants used as dietary supplements. The determination of copper in solid samples by DSA–FAAS was made by using a conventional air–acetylene flame. Between 0.05 and 1.5 mg of each test, sample was weighed directly into a small polyethylene vial connected to the device used for solid introduction into the flame. Test samples were introduced into the flame as a dry aerosol using a T-quartz cell set between the burner and the optical path. The T-quartz cell has a slit in the superior part by which the solid aerosol passes to the flame. A transient signal, evaluated as integrated absorbance, is produced and it is totally integrated in 2 s. Background signals always presented absorbance values less than 0.1. It was found a characteristic mass of 0.8 ng Cu and absolute limit of detection of 1.2 ng (3 s), or 1.2 μg g⁻¹ if a sample mass of 1 mg was used. Optimized conditions for air flow rate, flame stoichiometry, and so on were established as well. No excessive grinding of the samples was needed and samples with particle of size less than 80 μm were used throughout. No statistical difference between the results from the proposed system and those obtained by sample digestion and determination by conventional FAAS was observed. With the proposed procedure, more than 50 test samples can be analyzed in 1 h and it can be easily adapted to conventional spectrometers for FAAS.     

Crystallization kinetics of polyamide 6 containing pigments

In terms of the Avrami equation, the effects of selected organic pigments on the kinetic parameters of the isothermal crystallization of coloured polyamide 6 were examined in the temperature range 468–478 K. It was found that B Blue and BB Red are active nucleating agents, which is acribed to their crystalline structure. G Orange slightly accelerates the crystallization of PA 6 at lower temperatures and concentrations, whereas in other conditions its effect is the opposite.The isothermal data were confirmed by the results of non-isothermal crystallization. The degree of supercooling corresponding to the peak of the DSC curve was the measured feature in this case.It was found that B Blue and BB Red reduce the free energy of formation of criticalsize nuclei by 20 and 12%, respectively, which is reflected in the rates of crystallization.

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Zusammenfassung Mit Hilfe der Avrami Gleichung wurde der Einfluß einiger ausgewählter organischer Pigmente auf die kinetischen Parameter der isothermen Kristallisation gefärbter Polyamide 6 im Temperaturbereich 468–478 K untersucht. B Blue und BB Red erwiesen sich als aktive Keimbilder, was mit Hilfe ihrer kristallinen Struktur erklärt werden kann. Bei niedrigeren Temperaturen und geringeren Konzentrationen wird die Kristallisation von PA 6 durch G Orange leicht beschleunigt, unter anderen Bedingungen kann das Gegenteil beobachtet werden. Die isothermen Daten wurden durch die Ergebnisse bei nichtisothermer Kristallisation bekräftigt. In diesem Falle wurde das dem DSC Peak entsprechende Maß an Unterkühlung untersucht. Es wurde gefunden, daß B Blue und BB Red die freie Energie zur Bildung von Keimen kritischer Größe um 20 bzw. 12% herabsetzen, was sich in den Kristallisationsgeschwindigkeiten widerspiegelt.

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, -6 468–478 . , , . , . . . , , , 20 12%, .

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This work was supported by the Polish Academy of Science, goal 01.14.     

Copper determination in biological materials by ETAAS using W-Rh permanent modifier

A tungsten-rhodium treatment on the integrated platform of a transversely heated graphite atomiser was used as a permanent chemical modifier for the determination of copper in biological materials by using digested samples as well as slurry sampling in electrothermal atomic absorption spectrometry. The W-Rh permanent modifier was as efficient as Pd+Mg(NO(3))(2) conventional modifier for obtaining good Cu thermal stabilisation in the digested and slurry samples. The permanent W-Rh modifier remained stable by approximately 300 and 250 firings when 20 mul of digested sample and 20 mul of slurry were delivered into the atomiser, respectively. In addition, the permanent modifier increased the tube lifetime up to 1370 and 744 analytical measurements in the digested and slurry samples, respectively. Also, when the W-Rh permanent modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime, resulting in a decreased need of re-calibration during routine analysis, increasing the sample throughput, and consequently diminishing the variable analytical costs. Detection limits obtained with W-Rh permanent modifier were 0.64 and 0.33 mug g(-1) Cu for digested (dilution factor 100 ml g(-1)) and 1.0% m/v slurries of biological materials, respectively. Results for the determination of copper in the samples were in agreement with those obtained with decomposed sample solutions by using Pd+Mg(NO(3)), since no statistical differences were found after applying the paired t-test at the 95% level.     

Synthesen von Heterocyclen, 85. Mitt.: Über die α-Acyllactonumlagerung von 5-Benzoyl-dehydracetsäure

Zusammenfassung Die vonButt undElvidge aufgefundenen Isomeren, 4-Hydroxy-5-acetyl-6-phenyl-pyron-(2) (1) und 4-Hydroxy-5-ben-zoyl-6-methyl-pyron-(2) (2), ergeben bei der Umsetzung mit POCl₃ und Eisessig 5-Benzoyl-dehydracetsäure (3). Im Gegensatz zur Dehydracetsäure² reagiert 5-Benzoyl-dehydracetsäure (3) in alkohol. HCl zum 2,6-Dimethyl-3-äthoxycarbonyl-5-benzoyl-pyron-(4) (6). Die Struktur dieser Verbindung wird auf chemischem und physikalischem Wege abgeleitet.Mit wäßr. HCl läßt sich3 in 2,6-Dimethyl-5-benzoyl-pyron-(4) (5) umwandeln.

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The isomeric compounds¹ 4-hydroxy-5-acetyl-6-phenyl-pyron-2 (1) and 4-hydroxy-5-benzoyl-6-methyl-pyron-2 (2) yield 5-benzoyl-dehydroacetic acid (3) if with glacial acetic acid and POCl₃. In contrast to dehydroacetic acid² 5-benzoyl-dehydroacetic acid (3) reacts in ethanolic HCl to 2,6-dimethyl-3-carbethoxy-5-benzoyl-pyron-(4) (6).However, with aquenous HCl3 is converted to 2.6-dimethyl-5-benzoyl-pyron-(4) (5).

     

CuI/glycerol mediated stereoselective synthesis of 1,2-bis-chalcogen alkenes from terminal alkynes: synthesis of new antioxidants

(E)-1,2-Bis-chalcogen alkenes were stereoselectively prepared in good yields by the addition of diorganyl dichalcogenides to terminal alkynes using CuI/Zn/glycerol as a recyclable catalytic system. The antioxidant activity in vitro of four (E)-1,2-bis-chalcogen alkenes synthesized was evaluated and (E)-1,2-bis-(4-methoxyphenylselanyl)styrene 3b presented excellent activity. The catalytic system used in the synthesis was recovered and used directly up to 5 cycles without loss of activity.     

Synthesis of (Z)-N-alkenyl-β-arylselanyl imidazoles via additive-free nucleophilic addition of imidazole to arylselanylalkynes

We present herein our results on the nucleophilic addition of imidazole to a range of arylselanylalkynes by simple heating in DMF without any additives to give (Z)-1-(1-organyl-(2-arylselanyl)vinyl)-1H-imidazoles. The reactions were performed under mild conditions with a range of arylselanylalkynes in good yields and with high regio- and stereoselectivity to give the respective (Z)-arylselanyl alkene as the only isomer.     

Thermal investigation on polymorphism in sodium saccharine

The thermal behavior of sodium saccharin polymorphic forms was investigated using thermogravimetry and differential scanning calorimetry, while structural changes during the dehydration processes were monitored by X-ray powder diffraction. In solid state, sodium saccharine may exhibit three forms: anhydrate, 2/3 hydrate (triclinic), and 15/8 hydrate (monoclinic) ones. In this investigation, it was established that monoclinic and triclinic forms compose an entantiotropically related polymorphs system. At 82 °C, the 15/8 hydrated monoclinic form is converted to 2/3 hydrated triclinic form, which showed to be the more thermodynamically stable form at room temperature. Spontaneous solidification leads to the formation of triclinic cell setting, and additionally, spontaneous hydration of the anhydrous form leads to formation of 2/3 hydrated triclinic form.