Characterisation of stabilizers in polyamide using DSC technique

Antioxidants are added to the polymers to suppress oxidation during the service life. The paper deals with determination of stabilizer (VANOX-SKT) antioxidant in polyamides using a differential scanning calorimeter. Normally the amount of antioxidants is determined using HPLC method which takes more than 48 hours for sample preparation. A series of polyamide samples with known content of antioxidants (0.0–0.8%) are analysed using DSC form –50 to 350 °C in oxygen atmosphere keeping Al-crucibles open. For all the compositions a linear relationship was found forH (heat of degradation) and induction time under isothermal conditions at 220 °C which enables the antioxidant VANOX-SKT to be determined in unknown samples.

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Zusammenfassung Zur Unterdrückung der Oxydation von Polymeren während der Nutzungsdauer werden diese mit Antioxydationsmitteln versetzt. Die vorliegende Arbeit beschäftigt sich mit der Bestimmung von Stabilisatoren (VANOX-SKT Antioxydans) in Polyamiden mit Hilfe eines Differential-Scanning-Kalorimeters. Auf herkömmliche Art und Weise wird der Antioxydansgehalt mittels HPLC bestimmt was jedoch wegen der Probenvorbereitung mehr als 48 Stunden dauert. Mittels DSC von –50 bis 350 °C in Sauerstoffatmosphäre in offenen Aluminiumtiegeln wurde eine Reihe von Polyamidproben mit bekanntem Antioxydansgehalt (0,0–0,8%) untersucht. Für alle Zusammensetzungen konnte zwischen der ZersetzungswärmeH und der Induktionszeit unter isothermen Bedingungen bei 220 °C ein linearer Zusammenhang festgestellt werden, welcher die Bestimmung des VANOX-SKT Antioxydansgehaltes von unbekannten Proben erlaubt.

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. ( -) . , 48 -. (0–0,8%) – 50 + 350 °C. 220 °C H ( ) , - .

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One of the authors (PSJ) is thankful to Perkin-Elmer AG,Switzerland and Jnuig Berchtotd, EMS-Chemie AG, for supporting the above work.     

Intramolekulare 1,3-dipolare Cycloadditionen von Diarylnitriliminen aus 2,5-Diaryltetrazolen

Intramolecular 1,3-Dipolar Cycloadditions of Diaryl-nitrile-imines Generated from 2,5-Diaryl-tetrazoles Alkenyl-substituted diaryl-nitrile-imines – generated by photolysis or thermolysis of alkenyl-substituted 2,5-diaryl-tetrazoles - undergo a regioselective intramolecular [2 + 3] cycloaddition to yield new heterocyclic compounds, e. g. fused 2-pyrazolines. With alkinyl derivatives, the corresponding pyrazoles have been formed. UV evidence is given for the intermediate nitrile-imine at ? 190°. The latter can be trapped using an excess of carboxylic acid (UV evidence for a new intermediate at ? 120°). In this case, the corresponding rearranged addition product N′-acyl-N′-aryl-benzohydrazide is isolated in good yield.     

Time resolved fluorescence spectroscopy

Time correlated single photon counting was used to investigate solvent dynamics of laser dyes in a polar, viscous solvent. The resolved total luminescence spectra of oxazine 4 in 2-methyltetrahydrofuran (2-MTHF) have been measured and solvent relaxation observed.     

Thermisch und photochemisch induzierte intramolekulare, 1,3-dipolare Cycloadditionen von 5-(2-Allyloxyphenyl)-2-phenyltetrazol. Vorläufige Mitteilung. 54 Mitteilung über Photoreaktionen

Thermal and Photochemically Induced Interamolecular 1,3-Dipolar Cycloaddition Reactions of 5-(2-Allyloxyphenyl)-2-phenyltetrazole The title compound 5 is easily obtained by a recently described procedure (Scheme 2). The tetrazole 5 reacts at 165–170° or on irradiation at room temperature to yield 2-phenyl-3,3a-dihydrochromano[4,3-c]pyrazole ( 7 , Scheme 3), which probably arises by intramolecular [3+2]-cycloaddition of the intermediate nitrilimine. Dehydrogenation of 7 with chloranil leads to 2-phenylchromano[4,3-c]pyrazole ( 8 , Scheme 3).     

Further studies on polycyclic arene sulfides. Preparation and mutagenic activity of 9, 10, 10a, 11a‐tetrahydrotriphenyleno[1,2‐b]‐thiirene, 1a,2,3,10b‐tetrahydro‐5H‐thiereno[3,4]benzo[1,2‐b]fluorene and 1a,2,3,11b‐tetrahydroacenaphtho[1′,2′:6,7]naphth[1,2‐b]thiirene

The title compounds 6 , 8 and 10 , which are dihydroarene sulfides of the environmental pollutants triphenylene, benzo[b]fluorene and benzo[k]fluoranthene, have been synthesized from the corresponding epoxides and N,N‐dimethylthioformamide. The mutagenicity of the episulfides has been investigated using Salmonella typhimurium strains TA98 and TA100. While compounds 6 and 10 were mutagenic, the tetrahydrobenzo[b]fluorene episulfide 8 was inactive.     

Simultaneous trace determination of nine organic UV-absorbing compounds (UV filters) in environmental samples

A new sensitive method has been successfully developed and validated for the simultaneous determination and quantification of nine estrogenic UV filters (benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-4, 4,4-dihydroxybenzophenone, ethyl-4-aminobenzoate, 2-ethyl-hexyl-4-trimethoxycinnamate, 3-(4-methylbenzylidene)-camphor, 3-benzylidene-camphor) in different environmental matrices. After optimisation of extraction conditions for the best recovery of polar to lipophilic compounds from fish tissue and a subsequent lipid clean-up in HPLC, fish extraction recoveries exceeded 72% for all nine UV filters. Identification and quantification of compounds was performed for lipophilic UV filters with gas chromatography-electroionisation-mass spectrometry and for polar and mid-polar compounds with liquid chromatography coupled to electrospray ionisation mass spectrometry. Instrumental detection limits (IDL) varied between 5 and 260 pg injected and method detection limits (MDL) were in the low ng/g lipids range for all test compounds. The described analytical methods are shown to be useful to screen for estrogenic UV filters in environmental samples such as fish and polar organic chemical integrative samplers.     

Intramolekulare 1,3-dipolare Cycloadditionen mit alkenyl-substituierten 3,4-Diarylsydnonen

Intramolecular 1,3-Dipolar Cycloaddition Reactions of Alkenyl-substituted 3,4-Diarylsydnones The 3,4-diarylsydnones 1 and 12a–e with an allyl or alkenyloxy substituent on the N(3)-phenyl group have been synthesized by classical methods starting from 2-allylaniline and the corresponding alkenyloxyanilines, respectively (Schemes 2 and 3). Whereas the allyl-substituted sydnone 1 undergoes an intramolecular 1,3-dipolar cycloaddition at room temperature in solution to yield 13 (Scheme 4), the alkenyloxy-substituted sydnones 12a–e are thermally stable. On irradiation of 1 and 12a–d , formation of the fused dihydropyrazoles 2 and 14a–d (Schemes 1 and 5) is observed. In the case of 12d , the yield of 14d is very low, and the symmetric 1,2,3-triazole 15a has been isolated as the main product. A very likely reaction mechanism for the formation of the photoproducts involves decarboxylation of the sydnones to give a nitrile-imine which undergoes an intramolecular 1,3-dipolar cycloaddition onto the C?C bond.     

Octahedral Complexes with Predetermined Helical Chirality: Xylene-Bridged Bis([4,5]-pineno-2,2'-bipyridine) Ligands (Chiragen[o-, m-, p-xyl]) with Ruthenium(II)

Tetradentate ligands are obtained by joining two optically active [4,5]-pineno-2,2'-bipyridine molecules in a stereoselective reaction, where two new stereogenic centers are created. These ligands are new members of the chiragen family that form OC-6 complexes with predetermined helical chirality. Ru(II) complexes with 4,4'-dimethyl-2,2'-bipyridine occupying the remaining coordination sites have been synthesized with all three new ligands. Characterization of the ruthenium complexes by NMR spectroscopy confirm C(2)-symmetric structures in solution. CD spectra show that the complexes are composed of only one helical diastereomer with the expected absolute configurations. In addition, a strong chiral amplification is observed, if precursors of low enantiomeric purity are used. This is due to the inability of ligands that are heterochiral in the two bpy moieties to coordinate to one center. X-ray structural data were obtained for the complex Delta-[RuCG[o-xyl](4,4'-DMbpy)](PF(6))(2). Crystal data (Mo Kalpha, 298 K): trigonal, space group R3, a = 52.986(4) ?, c = 10.545(1) ?, V = 25639(4) ?(3), Z = 18, R1 = 0.087, and wR2 = 0.0986 for 2609 observed reflections.     

Bestimmung der Überġanġsfunktion eines Reġelkreises aus dessen frequenzġanġ

Summary A practical method for determining the transient responsef(t) of an automatic control system from the frequency responseF() is given. The real and imaginary part ofF()/ each are approximated by a series of auxiliary functions () with known corresponding time functions. A table of the most useful of these correspondences is included.The resulting transient response is obtained as one of the two sums equation (10a) or equation (10b) according to the choice of the real or imaginary part of the frequency response as the point of departure.As an example the frequency response with the imaginary part given in figure 1 is transformed to the transient response shown in figure 2 using the six auxiliary functions indicated in figure 1.