Spiegelsymmetrische Hexahydro-1,2,4,5-tetrazine aus Pyrazolidon-(3)-N,N-betainen – ein Beitrag zur „thermischen Dimerisierung”︁ von 1,3-Dipolen

Mirror-symmetric Hexahydro-1,2,4,5-tetrazines from Pyrazolidine-3-one-N,N-betaines—a Contribution to the „Thermal Dimerization”︁ of 1,3-Dipoles Chemical reactions, i.r., ¹H-n.m.r., and ¹³C-n.m.r. data show that the “thermal dimers” of pyrazolidine-3-one azomethinimines 2 , which till now accidentally formed during the synthesis of 2 from pyrazolidine-3-ones 5 and aldehydes 6 , are 5,11-diaryl-perhydro-dipyrazolo[1,2-a; 1′,2′-d][1,2,4,5]-tetrazine-1,9-diones 3 , i.e. mirror-symmetric hexahydro-1,2,4,5-tetrazines with (C-5) and (C-11) placed on the mirror plane. From DREIDING models and from the nonequivalence, concerning ¹³C-n.m.r., of the pairs of carbon atoms in the o- resp. m-positions of the aryl substituent I at (C-5) of the “dimers” 3 is derived that the rotation of I is sterically hindered (ΔG = 16,3 kcal/mole for 3b ), and that the preferred arrangement of I is perpendicular to the plane of the hexahydrotetrazine ring. The “thermal dimerization” of the 1,3-dipoles 2 is a complex series of two addition and elimination steps proceeding in the presence of catalytical amounts of pyrazolidine-3-one 5 and of H^⊕. The mechanism is rationalized, consequences are suggested concerning known “dimerizations” of 1,3-dipoles.     

Die Zusammensetzung ”︁oxidierter Fettsäuren”, ihr Gehalt als Beurteilungsgrundlage für erhitzte Fette und ihre Beziehung zur Verseifungsfarbzahl

Composition of “Oxidized Fatty Acids”, Their Content as a Basis for the Evaluation of Heated Fats and Their Relationship to Saponification Colour Number “Oxidized fatty acids”? obtained from various thermally oxidized fats according to DGF method C-III 3 (68) have been investigated. Empirical formula determined from molecular weight, and C-, H- and O-content, and the possible structural formulas are discussed. During oxidation the content of ?oxidized fatty acids”? increased parallel to the increased in saponification colour number E100%, 1 cm/470 nm. Contrary to other investigations, it has been proved that the relationship between saponification colour number and “oxidized fatty acids? is not affected by the material fried. Thus it is possible to use saponification colour number in combination with acid value as basis for the evaluation of heated fats.     

Quinone–Quinoneimine Tautomerism of Some Aminonaphthoquinonoid Dyes

Quinone–quinoneimine tautomerism of 7, 10–dihydroxy–2, 3, 4–trihydrobenzo f quinoxalin–6–one derivatives has been investigated by means of their n. m. r. and visible absorption spectra. The quinonoid ring protons gave signals in the range 5. 6–6. 1 p. p. m., while the benzenoid ring protons showed signals in the range 6. 9–7. 0 p. p. m. These differences in chemical shift were valuable in identifying the structure of the tautomer. Tautomerism was found to be largely influenced by the nature of the substituents and the polarity of the solvent, and the equilibrium shift to the quinoneimine form in polar solvents. The quinone form absorbed visible light at much longer wavelengths (by about 100 nm) than does the quinoneimine form. The isosbestic point of the tautomerism was observed at about 510 nm. The calculated absorption maximum of each tautomer obtained using the PPP MO method was correlated with the observed values to predict the principal tautomer in solution.     

Structural,spectroscopic and computational study of 5‐(substituted phenylazo)‐3‐cyano‐1‐ethyl‐6‐hydroxy‐4‐methyl‐2‐pyridones

Ten 5‐(substituted phenylazo)‐3‐cyano‐1‐ethyl‐6‐hydroxy‐4‐methyl‐2‐pyridones were studied (five new compounds) to provide insight into the electronic effects of diverse substituents located at different positions in their phenyl moieties. The structural features of these dyes were examined by combining experimental and theoretical approaches. The crystal structures of two derivatives were revealed by X‐ray crystallography and diverse packing modes owing to different intermolecular interactions (π–π stacking and lone pair–π interactions, as well as hydrogen bonds) were found. A study on lattice energy and energy related to the molecular pairs obtained from their crystal packing was performed. The tautomerism and ionisation of the dyes in ethanol or N,N ‐dimethylformamide solution were rationalised in terms of diazo component substitution pattern.     

Preparation of long-chain β-enaminones and β-diketones from long-chain 3,5-disubstituted isoxazole compounds

A series of long-chain compounds containing the β-enaminone functionality were prepared in yields ranging from 71 to 88% from their corresponding long-chain 3,5-disubstituted isoxazole precursors utilizing a Raney nickel-catalyzed reductive ring-opening procedure. These newly prepared multifunctional compounds were subsequently hydrolyzed under mild acidic conditions (pH 4–5) to give their corresponding long-chain β-diketones in yields ranging from 79 to 98%. Both the β-enaminone and β-diketone functionalized compounds were characterized by NMR, IR spectroscopy, GC-MS, and m.p. The mass spectra for these two classes of compounds, derived by utilizing electron impact ionization, gave distinctive McLafferty rearrangement fragmentation ions that clearly established the newly introduced functionality to reside at the C-2 and C-4 positions of the lipid’s alkyl chain. ¹H NMR spectra of the pure β-diketone compounds were complex owing to the keto enol tautomerism displayed by the β-diketone moiety. In solution the β-diketone compounds were shown to exist mainly in the enolic tautomeric form. Long-chain β-diketone compounds are known to be relatively common constituents of some plant waxes, and the overall procedure starting from soybean methyl esters provides a complementary approach to prepare these types of compounds.     

Spektroskopische Untersuchungen zur Strukturaufklärung von acyclischen,vinylogen Carbonsäure- und vierfach koordinierten P(O)-Säureaniliden

Spectroscopical Investigation for the Determination of the Structure of Acyclic, Vinylogous Carbon Acid Anilides and Quadruple Coordinated P(O)-Acid Anilides The ¹H-n.m.r., i.r. and u.v. spectra of the title compounds are reported and discussed. Because of the tautomerism of the NH-proton as well as the cis-trans-isomerism, 5 structures are possible. The enamine-imine-equilibrium is totally shifted to the side of the enamine form, while the distribution between cis- and trans-isomers depends on the existence of intra- or intermolecular hydrogen bonds, solvent-effects and the size of the substituents.     

Synthese eines „Ethyl-Brahmanols”︁

Synthesis of „Ethyl-Brahmanol”︁ The synthesis of the title compound ( 11 ) from ethylapopinene ( 5 ) by oxydation to the epoxide ( 6 ), rearrangement to “ethyl-α-campholene aldehyde” ( 7 ) and its aldol condensation is described.     

Quinone-Quinoneimine Tautomerism of 5, 8-Bis(donor) substituted 1, 4-Naphthoquinonoid Dyes

Quinone-quinoneimine tautomerism of 5, 8-bis(donor) substituted 1, 4-naphthoquinones have been investigated by means of their visible absorption spectra. Tautomerism was found to be influenced mainly by the nature of the substituents and the polarity of the solvents; the equilibrium shifted to the quinone form in the more polar solvents. The quinone tautomer absorbed visible light at much longer wavelengths (about 160–180 nm) than did the quinoneimine tautomer. Isosbestic points of the tautomerism were observed. The calculated absorption maximum of each tautomer, obtained by means of the PPP MO method, was correlated with the observed values to predict the principal tautomer in solution.     

Über “Stoffmenge” und Mischphasen-Kennzeichnung

Previous contributions to the notion of “quantity of a substance” (different from its mass for the needs of chemistry) are reviewed. Such a quantity is definable either as dimensionless (pure number of molecules, moles, equivalents …) or as having a new kind of dimension. Names, notations and dimensions are logically deduced for correlated quantities and fundamental constants (i.e. gazes and Faraday's constants). It may be generalised from pure substances to homogeneous mixtures.     

Spectral characterisation and computational studies of some novel phenylazoindol‐2‐one dyes

A series of novel phenylazo disperse dyes were prepared by coupling selected diazotised 3‐ or 4‐anilines with indol‐2‐one. The structures of the synthesised dyes were determined by spectroscopic and analytical methods. Solvent effects on the ultraviolet–visible absorption spectra of these novel dyes were studied. The colour of the dyes was evaluated with respect to the substituent therein. Acid and base effects on the visible absorption maxima of the dyes were also reported. The tautomerism of 3‐(phenyldiazenyl)indol‐2‐one was modelled by density functional theory at the B3LYP level. The ultraviolet–visible absorption spectra for the tautomers were reproduced with the time‐dependent density functional theory and semi‐empirical Zerner’s intermediate neglect of differential overlap/spectroscopic (ZINDO/S) method. The predominance of the keto–hydrazone tautomer was confirmed experimentally and theoretically.     

Toward “Rubbery” nanoparticles

The synthesis of electrically Conducting Natural Rubber (CNR) nanoparticles from natural rubber (cis 1, 4 polyisoprene) by a simple chemical doping technique is reported for the first time. Much before the establishment of conjugation as a precondition for polymers to be conducting a typical nonconjugated polymer like cis 1,4 polyisoprene was shown to develop intrinsic conductivity on doping. However, the possibility of developing conducting nanoparticles of natural rubber by doping has never been explored. Doping of natural rubber solution with Antimony pentchloride is found to lead to the formation of nanosized rubber particles with improved thermal stability and lower degradation characteristics than that of pristine rubber. Transmission electron microscopy and Dynamic Light Scattering experiments revealed a highly uniform dispersion of the particles with sizes in the range of 4 nm. The doped nanoparticles are found to retain “rubbery” properties of natural rubber and therefore these can be rightly termed as Rubber Nano particles. The development of nanoparticles of rubber assumes great significance in that it would lead to hitherto unknown applications for natural rubber in micro applications‐like sensors, and optoelectronics devices to macro applications such as compatible reinforcing fillers for elastomers and plastics to replace conventional fillers like carbon particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Antitermite Activities of Coumarin Derivatives and Scopoletin from <Emphasis Type="Italic">Protium javanicum</Emphasis> Burm. f.

The antitermite (termiticidal and antifeedant) activity of Protium javanicum Burm. f. extract was investigated. The ethyl acetate fraction was active. Scopoletin (1), quercetin, and stigmasterol were isolated by bioassay-guided fractionation. Scopoletin had the highest activity among the three compounds. In order to investigate the structure-activity relationship (SAR) of the methoxy and hydroxy groups at the C-6 and C-7 positions of the coumarin skeleton, we synthesized several coumarin derivatives whose chemical structures are similar to scopoletin. Scopoletin exhibited the strongest termiticidal activity among the 10 compounds tested, followed by 6-methoxycoumarin (3), 6-hydroxycoumarin (7), and umbelliferone (8). All compounds except coumarin (9) showed antifeedant activity.     

Polymer waste recycling over “used” catalysts

Catalytic degradation of high-density polyethylene (HDPE) was carried out under nitrogen using a laboratory fluidised bed reactor operating at 360 °C with catalyst to polymer feed ratio of 2:1 and at 450 °C with catalyst to polymer feed ratio of 6:1 under atmospheric pressure. The catalysts used in this study were ZSM-5, US-Y, ASA, fresh FCC (fluid catalytic cracking) commercial catalyst (Cat-A) and equilibrium FCC catalysts with different levels of metal poisoning were studied. The initial results for polymer degradation at 360 °C (catalyst to polymer ratio of 2:1) in a fluidised bed reactor in terms of the yield of volatile hydrocarbon products were: model catalysts>commercial FCC catalyst>E-Cats. However, when the process conditions more closely resembled to FCC conditions, the fresh commercial FCC catalyst was more favourable in terms of the yield of volatile hydrocarbon products. The degradation of HDPE over E-Cats although reduced was similar to ASA in product selectivity and yield, and the level of metal contamination did not affect the product stream generated. A simple economic evaluation of polymer recycling process is reported showing that a catalytic system based on E-Cats appears comparable in costs to a commercial thermal cracking plant.     

Let's call it “color‐gamut rendering”

The term “color gamut” historically has been associated with color output such as optimal color stimuli and additive and subtractive imaging systems. Recently, this term has been used with input devices such as scanners and digital cameras. It is proposed that the term “color‐gamut rendering” should be used instead of input devices. This clarifies the distinction between input (analysis) and output (synthesis) color systems in terms of the effect of an input system on defining the colorimetric properties of an output system. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 334–335, 2007     

Solvatochromism,halochromism, and azo–hydrazone tautomerism in novel V‐shaped azo‐azine colorants – consolidated experimental and computational approach

The azo–hydrazone tautomerism, solvatochromism, and halochromism in four novel V‐shaped asymmetrical acceptor‐π‐donor‐π‐acceptor (A‐π‐D‐π‐A) compounds were examined. They contain 2,7,15,16‐functionalised benzophenazine cores connected to the anchoring electron‐deficient phenyl core via azo linkers and 2,7‐position fused with anthraquinone. These compounds derived from 2‐hydroxy‐1,4‐napthaquinone (lawsone) have been prepared in moderate to good yields. The synthesis involved the diazotisation of substituted aromatic amines, coupling onto 2‐hydroxy‐1,4‐napthaquinone, and further condensing the resulting azo compounds with 1,2‐diaminoanthraquinone in acetic acid. The absorption wavelengths of the dyes in different solvents were in the range 500–720 nm. The spectral changes of the synthesised azo‐azine compounds in different pH indicated the formation of hydrazone tautomer in acidic pH and of azo tautomer in alkaline pH. Density functional theory was used to assess the tautomers in terms of geometry and position of the tautomeric equilibrium. Time‐dependent density functional theory calculations allowed us to assign the electronic transitions (>90%) of the low‐energy bands.     

Darstellung,Struktur und Reaktivität quartärer Ammoniumcellulosate

Tetraalkylammonium cellulosates were prepared by means of an exchange reaction between cellulose and tetraalkylammonium methoxides in anhydrous methanol and dimethylsulfoxide up to a degree of substitution of about 0,7 without chain degradation. The course of this reaction and the structure of the cellulosates in comparison to lithium and sodium cellulosate has been studied. The reaction rate and the equilibrium substitution decreased with increasing size of the cation in the methoxide. The distribution of the alcoholate groups in equilibrium at C-2, C-3 and C-6 of the glucopyranosyl unit in the cellulosates, which was investigated by methylation, hydrolysis of the methylcelluloses, and analysis of the methylglucoses by gas chromatography, was independent of the nature of the cation. Under the given reaction conditions the hydroxyl group at C-2 was more acidic than those at C-3 and C-6, while for the latter practically no difference was found. The tetraalkylammonium cellulosates are highly reactive intermediates for the preparation of cellulose derivatives. The reactivity of the cellulosates increased with increasing size of the cation, Li^⊕ < Na^⊕ < N(CH₃)₄^⊕ <[(CH₃)₃N? CH₂? C₆H₅]^⊕.     

The Electrolytic “Sintering” of Nickel Powder

Adherent and coherent deposits of nickel sponge similar to sintered nickel may be made from sulphate, chloride, fluoborate or sulphamate nickel plating solutions containing nickel powder in suspension, providing the concentration of free acid is maintained sufficiently high to inhibit co-depesition of Ni(OH) In nitrate solution, cathodic reduction of nitrate and deposition of Ni(OH)₂ predominates.     

Interrogation of “surface,” “skin,” and “core” orientation in thermotropic liquid‐crystalline copolyester moldings by near‐edge X‐ray absorption fine structure and wide‐angle X‐ray scattering

Injection molding thermotropic liquid‐crystalline polymers (TLCPs) usually results in the fabrication of molded articles that possess complex states of orientation that vary greatly as a function of thickness. “Skin‐core” morphologies are often observed in TLCP moldings. Given that both “core” and “skin” orientation states may often differ both in magnitude and direction, deconvolution of these complex orientation states requires a method to separately characterize molecular orientation in the surface region. A combination of two‐dimensional wide‐angle X‐ray scattering (WAXS) in transmission and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy is used to probe the molecular orientation in injection molded plaques fabricated from a 4,4′‐dihydroxy‐α‐methylstilbene (DHαMS)‐based thermotropic liquid crystalline copolyester. Partial electron yield (PEY) mode NEXAFS is a noninvasive ex situ characterization tool with exquisite surface sensitivity that samples to a depth of 2 nm. The effects of plaque geometry and injection molding processing conditions on surface orientation in the regions on‐ and off‐ axis to the centerline of injection molded plaques are presented and discussed. Quantitative comparisons are made between orientation parameters obtained by NEXAFS and those from 2D WAXS in transmission, which are dominated by the microstructure in the skin and core regions. Some qualitative comparisons are also made with 2D WAXS results from the literature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Antioxidative Effect of “Herbalox” on Edible Oils

Antioxidative effect of BHA (Butylated hydroxyanisole) and rosemary extract (Herbalox Type 0) in soybean and sunflower seed oil were investigated. Stability to oxidation was determined by measurement of induction time with the Rancimat 679 at 100°C. Changes in control (no antioxidant added) and experimental oil samples were monitored. The addition of antioxidants reduce oxidation thus increasing product stability. Presence of synthetic antioxidant BHA in sunflower seed oil at the concentration of 0.02% (w/w) increases induction time from 6.0 to 8.09 hours. The results obtained indicated higher synthetic antioxidant efficacy compared with natural Herbalox Type 0 antioxidant, as the induction time for the later one, used at the same concentration, increased from originally 6.0 to 6.67 hours.     

Storage hardening and “abnormal” groups in guayule rubber

The hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.