Copolymers of tetrafluoroethene with chlorotrifluoroethene and with bromotrifluoroethene

Tetrafluoroethene (TFE)–chlorotrifluoroethene (CTFE) and TFE–bromotrifluoroethene (BTFE) copolymers have been synthesized by solution copolymerization over the entire range of comonomer composition. Crystallinity data are reported and first- and second-order transitions have been investigated by DSC. Glass transition temperatures of TFE-CTFE copolymers vary in a nonlinear fashion in the range defined by the homopolymers conforming best to the Johnston equation; the behavior in the TFE-BTFE system is more linear. Whereas TFE-BTFE copolymers show a steep decrease of melting temperature at higher BTFE content, due to the amorphous character of the polymers, more regular behavior was found for TFE-CTFE copolymers. Enthalpies of fusion are also reported. The results are discussed in relation to copolymer composition and structure and are compared with data on tetrafluoroethene–hexafluoropropene (FEP) fluorocarbon resins.     

Asymmetric sorbents with N-carboxymethyl-L-valine and with N-carboxymethyl-L-aspartic acid

Conclusions The asymmetric sorbents with N-carboxymethyl-L-valine with N-carboxymethyl-L-aspartic acid can be used to resolve racemates by the ligand-exchange chromatography method. Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2378–2380, October, 1976.     

Reactions of indole derivatives with cardioprotective activity with reactive oxygen species. Comparison with melatonin

We have previously reported on the synthesis of novel indole derivatives containing an amine-triazole moiety (1a-d, 2a-c), and their antioxidant activity on in vitro non-enzymatic rat hepatic microsomal lipid peroxidation. Some of the compounds showed protective activity against oxidative injury of ischemic myocardium. In the present paper we investigated the interactions of these derivatives with reactive oxygen species, in order to find a mechanism of their antioxidant capacity and to identify structural characteristics responsible for these properties. These interactions were compared with melatonin, which is also an indole derivative. The antioxidant profiles of the compounds were established by different in vitro protocols as follows: 1) by the interaction of the compounds with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, 2) their scavenging effects on superoxide anions using an enzymic system of xanthine-xanthine oxidase, 3) their inhibitory effects on xanthine oxidase and 4) their ability to scavenge hydroxyl radicals by comparison with dimethyl sulfoxide (DMSO) for *OH. All compounds were found to interact with DPPH, most of them to be superoxide anion scavengers and to be strong hydroxyl radical scavengers. Derivatives 1a and 1d substituted on the nitrogen of the indolic nucleus were found to have better antioxidant properties than the reference compounds used and melatonin.     

Voltammetry with a Fluoride-Selective Electrode with Solid-Phase Reference System

Experimental results obtained in a study of the voltammetric response of an all-solid fluoride-selective electrode based on LaF₃ (Eu²⁺ 0.8 mol %), LaF₃ (Sr²⁺ 5 mol %) and CeF₃ (Sr²⁺ 5 mol %) single crystals brought in contact with Ag, Bi, and Sn metal samples are presented. The method of cathodic inversion voltammetry was applied to study the reduction of La³⁺ and Ce³⁺-cations from the rigid sublattice of solid electrolytes, which determines the threshold of the electrochemical stability of a membrane. Anodic inversion voltammetry was used to investigate the characteristics of solid-phase generation of metal fluorides at the interface between the fluoride-selective electrode and metals.     

Multielement analysis with ICP-AES-possibilities for quality control with CRMs

Summary An analysis using Certified Reference Materials (CRMs) together with routine samples is by far the best approach for quality control in multielement analysis of environmental samples. The selection of the correct CRM is thus the first important step for all reliable analysis. The chosen material should have a similar matrix, similar concentration of the element(s) of interest and a sufficient number of well-certified elements. For the analysis of samples from the Environmental Specimen Bank only a few CRMs could be successfully used. These were analyzed for a considerable period of time, together with the routine samples for quality control. The results of these analyses were compared with the certified values.     

Treatment of Wool with Laccase and Dyeing with Madder

This research has explored the effect of laccase (Denilite ІІ S) on the physical properties of the wool fabric and confirms the anti-felting of wool. In the experiment, laccase was applied to a wool fabric and different characteristics including weight loss, strength, alkali solubility, felting shrinkage, water drop absorption, and dye ability with madder were studied. The surface morphology of the wool fabrics was also observed by scanning electron microscope. The results indicated that the wool fabric treated with laccase has a higher water drop absorption, lower felting shrinkage, and lower values of a ^* and b ^*. Treatment of a wool fabric with 10% or lower percentage of laccase reduced the fabric weight but increased the tensile strength. However, using higher concentration of laccase reduced fabric weight and tensile strength. The dyeing of laccase pre-treated wool fabric with madder indicated a lower lightness.     

Fluorination with xenon difluoride. Reaction with halogenated hydrocarbons

Filler and coworkers [1-5] have demonstrated the utility of xenon difluoride as a selective fluorinating agent for aromatic hydrocarbons in the liquid phase, while Mackenzie and coworker [6] have fluorinated aromatic compounds in the vapour phase. We have developed a fluorination reaction of phenyl substituted olefins resulting in high yields of vicinal difluorides [7,8] and trifluoroacetates, depending on the catalyst. In our continued interest in the use of xenon difluoride as a mild fluorinating agent for fluorination of organic compounds, we have tries to fluorinate some heterocyclic ring systems, e.g. imidazo-(1,2-b)-pyridazine, under conditions similar of those used for fluorination of phenyl substituted olefins [7,8,9] (room temperature, methylene chloride as solvent, hydrogen fluoride as catalyst). It is well known that heteroaromatic compounds are less reactive toward electrophilic substitution reactions then aromatic hydrocarbon systems. However, it has been shown that bromination of imidazo-(1,2-b) -pyridazine results in 3-bromo products [10], while in chlorination with phosphorus pentachloride [11], the entering order of chlorine atoms is at position 3 > 2, 7 > 8 > 6 (Radical reactions).     

Microfibrillated cellulose with sizing for reinforcing composites with LDPE

Microfibrillated cellulose (MFC) fibers were acylated by the sizing agent, alkenyl succinic anhydride (ASA) reagent in an aqueous medium, by simple impregnation. The chemical modification was confirmed by Fourier transform infrared spectroscopy and solid-state ¹³C NMR. All the samples were combined with low-density polyethylene and the morphology, thermal properties, mechanical properties and water absorption behavior of the ensuing composites were investigated. The chemical modification of the MFC with ASA improved the interfacial adhesion with the matrix and hence the mechanical properties of the composites while decreasing their water uptake capacity. In addition, it was shown that the degree of substitution strongly influenced the performance of the composites.     

Reaction of isatin with alkylating agents with acidic methylenes

The reaction of isatin (1) with different alkyl halides 2 and alkaline carbonates in aprotic polar solvents leads mainly to N-alkyl derivatives 3. The use of alkylating agents that have acidic methylenes leads to competitive formation of the corresponding epoxide 5. The formation of 5 is favored by low-polarity solvents at low temperatures and strong bases. Epoxides 5c, d obtained using NaEtOH/EtOH at 0–5 °C are transformed into the corresponding 4-quinolinones 6 at higher temperatures. The use of Ag₂CO₃ allows obtaining compounds 3 as major products, along with varying amounts of labile O-alkyl derivatives 4 and dimerization products.     

Nanocomposite material with immobilized acid-base dyes conjugated with polysaccharides

Water-soluble acid-base dyes xylenol orange and methyl red are linked by covalent bonds to chitosan macromolecules; neutral dye red is bound to carboxymethyl cellulose to prevent their washing-off from silicate matrix. Dye conjugates were then immobilized by modified sol-gel method using silicate precursor compatible with polysaccharides. Synthesized hybrid nanocomposite materials are optically transparent, which makes it possible to apply them to develop sensors for measuring pH. Spectral characteristics of dyes, their conjugates, and prepared nanocomposites with silicate matrix are studied in detail. It is shown that xylenol orange, which is linked with chitosan by covalent bonds, is the most suitable dye for the development of sensor materials because the conjugation by carboxyl groups, which do not directly bound with chromophore center, does not deteriorate the spectral properties of this dye. In the cases of methyl red and neutral red dyes, undesirable changes in their properties in the course of conjugation are caused by the covalent binding by functional groups, which are auxochromes directly affecting all spectral characteristics of dyes. An increase in the solubility of polysaccharide in water can also positively affect the covalent binding of dyes with chitosan that allows polysaccharide to be used in neutral and alkaline media.     

High-temperature reactions of trichloroethylene with toluene and with methanol

Conclusions The reactions of trichloroethylene with toluene and with methanol, conducted 560–570°, leads to the formation of a mixture of the isomers R-CH=CCl₂ and cis- and trans-R-CCl=CHCl (R=CH₂C₆H₅ and CH₂OH).Translated from Izvestiya Akademii Nauk SSSR. Seriya Khimicheskaya, No. 12, pp. 2777–2778, December, 1967.We thank E. D. Lubuzh and A. V. Kessenikh for determining and interpreting the IR and NMR spectra.     

Extraction with supercritical gases in coupling with thin-layer chromatography

Summary Numerous substances can be extracted from samples by supercritical gases, e.g. either carbon dioxide or nitrous oxide in the fluid condition at temperatures of 40° C and pressures between 70 and 400 bar. An apparatus for such solvent-free extraction in the analytical field is described. It is coupled directly with a receiving apparatus for subsequent thin-layer chromatography. Three examples with corresponding chromatograms show the possibilities and advantages of this new coupling procedure.

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Extraktion mit überkritischen Gasen in Kopplung mit der Dünnschicht-Chromatographie1. Mitteilung: Aufbau der Apparatur, Handhabung und Anwendung

Zusammenfassung Zahlreiche Substanzen lassen sich mit überkritischen Gasen aus Proben fraktioniert abtrennen. Als Gase dienen z.B. Kohlendioxid und Distickstoffoxid im fluiden Zustand, d.h. bei Temperaturen von 40° C und Drücken zwischen 70 und 400 bar. Für derartige lösungsmittelfreie Extraktionen im analytischen Bereich wird eine Apparatur beschrieben. Sie ist direkt mit einer Auffangapparatur zur anschließenden Dünnschicht-Chromatographie gekoppelt. An 3 Beispielen mit entsprechenden Chromatogrammen werden die Möglichkeiten und Vorteile dieser neuen Kopplungsmethode demonstriert.

     

Enthalphy of mixing of bromobenzene with n-alkanes,with cyclohexane,and with benzene

A dynamic flow microcalorimeter of the Picker design was used to measure enthalpies of mixing at 298.15 K and atmospheric pressure of the six binary systems bromobenzene + n-hexane, + n-heptane, + n-nonane, + n-tetradecane, + cyclohexane, and + benzene. Within the homologous series of n-alkane systems, the interaction parameter, h₁₂, calculated from rigid-lattice group contribution theory, decreases weakly with increasing chain length of the alkane. This behavior is quite analogous to that observed with chloro-derivatives of benzene + n-alkane.     

Reactions of amines with a dimer of hexafluoropropene and with a perfluorovinyl sulfide prepared with hexafluoropropene

Some reactions of amines with a perfluorovinylsulfide, (CF₃)₂CFSC(CF₃)CFCF(CF₃)₂, prepared from hexafluoropropene (HFP) and sulfur [1] are compared to reactions of the same amines with the thermodynamic dimer of HFP, (CF₃)₂CCFCF₂CF₃. Many new ketenimines, eneamines, amidines, nitriles, and quinoline derivatives are reported.