Thermal dehydrochlorination of poly(vinyl chloride)—epoxidized butadiene/styrene triblock copolymer blends

The effect of the type of epoxidized butadiene/styrene block copolymer [ESBS; linear (B/S) or radial (E(B/S)_n), containing 0–27% of epoxy groups] on the thermal dehydrochlorination of poly (vinyl chloride) (PVC)-ESBS blends (ESBS content 10%) was investigated in the temperature range 170–180 °C, under a non-oxygen atmosphere. Thermal stability of the PVC-ESBS blends was estimated on the basis of induction time, t₀, and maximum rate of hydrochloride emission, V_max from the system. It was found that, for a similar degree of epoxidation of the SBS copolymer, the induction time i.e. the time after which emission of HCl begins, is longer in the series PVC < PVC-SBS < PVC-EB/S < PVC-E(B/S)_n, and the same is true for thermal stability. However, the maximum rate of emission of HCl is lowest in the case of PVC-EB/S blends, in the range of molar ratios from 0.5 to 2.0 × 1O⁻². On the basis of the dependence V_max = f(EB/VC), it was found that there is a certain content of epoxidized butadiene (EB) units in a mixture which causes the optimum stability of poly (vinyl chloride) during heating. During thermal destruction of the PVC-ESBS blends, the HC1 evolved undergoes addition both to epoxy fragments and to double bonds. The degree of conversion of EB units in time t₀ is 20% at 170 °C and 30% at 180 °C. The glass transition temperature, T_g, of PVC in the PVC-ESBS blends shifts towards higher temperatures by about 6–8 °C, proving the existence of crosslinking processes during moulding of the blends. The epoxidized butadiene/styrene radial block copolymer, E(B/S)_n, is a better thermal stabilizer of PVC than the linear EB/S copolymer.     

Spectral and thermal studies of light lanthanide 4-chlorophthalates

Conditions for the preparation of light lanthanide 4-chlorophthalates were investigated and their composition, solubility in water at 295 K, IR spectra and thermal decomposition were determined. 4-Chlorophthalates of La–Nd(III) were prepared as complexes with general formula NaLn[ClC₆H₃(CO₂)₂]₂, whereas compounds of Sm and Eu have general formula Ln₂[ClC₆H₃(CO₂)₂]₃·6H₂O. During heating all complexes decompose to oxides with intermediate formation of oxochlorides. The carboxylate groups in the complexes studied are bidentate bridging (Sm, Eu) or bidentate chelating and bridging (La–Nd).     

Crystal Structure and Spectral Characterization of a Rare Example of a Salen-Type Zinc Complex with Neutral Monodentate Oxygen Donor Ligands Coordination

Summary. The new zinc complex of the N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand as a product of the [2 + 1] Schiff base condensation process was synthesized in the one-step metal-promoted reaction between salicylaldehyde and 4-methyl-1,3-phenylenediamine in ethanol in the presence of zinc chloride. The two potentially tetradentate N₂O₂ Schiff bases function as neutral monodentate ligands involving only one oxygen atom in coordination. This rare coordination pattern of a mononuclear salen-type zinc complex was revealed by X-ray crystallography and correlated with spectroscopic characterization.     

Preparation and properties of yttrium,lanthanum and lanthanidep-nitrobenzoates

The conditions of the formation of rare earth elementp-nitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K were determined (their solubilities are of the order of 10^–3 mol dm^–3). The IR and X-ray spectra for the prepared complexes and the dehydrated rare earthp-nitrobenzoates were recorded. All obtained complexes are crystalline compounds. The conditions of thermal decomposition of the complexes were also studied. It was found that on heating above 573 K the complexes decompose explosively and undergo a melting process at the same time. Therefore the thermal decomposition for complexes being investigated was carried out in the temperature range 273–573 K. From the obtained results it follows that during the dehydration process no transformation of the nitro group to nitrito occurs.

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Herstellung und Eigenschaften von Y, La und Lanthaniden-p-nitrobenzoaten

Zusammenfassung Die Bedingungen zur Darstellung von Y-, La- und Lanthaniden-p-nitrobenzoaten wurden untersucht. Ihre quantitative Zusammensetzung und ihre Wasserlöslichkeit bei 298 K wurden bestimmt (die Löslichkeit ist in der Größenordnung 10^–3 mol dm^–3). Die Infrarot- und Röntgenspektren der erhaltenen Komplexe sowie derp-Nitrobenzoate der seltenen Erden nach der Dehydratisierung wurden gemessen und dabei festgestellt, daß es sich um kristalline Verbindungen handelt. Das thermische Verhalten der erhaltenen Komplexe wurde untersucht: Sie zerfallen über 573 K explosiv und schmelzen zugleich. Der thermische Zerfall der erhaltenenp-Nitrobenzoate der seltenen Erden wurde im Temperaturbereich von 273–573 K untersucht. Es wurde festgestellt, daß die Y-, La- und Lanthaniden-p-nitrobenzoate bei Temperaturzunahme oder im Dehydratisierungsprozeß keiner Umgruppierung in entsprechende Nitritoverbindungen unterliegen.

     

Crystal Structure and Spectral Characterization of a Rare Example of a Salen-Type Zinc Complex with Neutral Monodentate Oxygen Donor Ligands Coordination

The new zinc complex of the N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand as a product of the [2 + 1] Schiff base condensation process was synthesized in the one-step metal-promoted reaction between salicylaldehyde and 4-methyl-1,3-phenylenediamine in ethanol in the presence of zinc chloride. The two potentially tetradentate N₂O₂ Schiff bases function as neutral monodentate ligands involving only one oxygen atom in coordination. This rare coordination pattern of a mononuclear salen-type zinc complex was revealed by X-ray crystallography and correlated with spectroscopic characterization.     

Pentaaza macrocyclic ytterbium(III) complex and solvent controlled supramolecular self-assembly of its dimeric mu-eta 2:eta 2 peroxo-bridged derivatives

The unprecedented template action of ytterbium ion in the synthesis of pentaaza macrocyclic Schiff bases is exemplified by isolation and definitive identification of the seven-coordinate pentagonal bipyramidal complex with the formula of [YbLCl(2)]ClO(4) (1), where L is 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),2,13,15,17-pentaene, providing the first example of crystallographically characterized pentaaza macrocyclic ytterbium complex. For the first time the spectrum of the (2)F(7/2) --> (2)F(5/2) transition has been obtained for a molecular complex of ytterbium with organic ligands in which all ligand-field components of the ground and excited state are well displayed at room temperature. This complex is capable of forming a dimeric peroxo Yb(2)(mu-eta(2):eta(2)-O(2))L(2)(4+) (2) derivative containing the biologically significant planar side-on doubly bidentate coordination mode of the peroxide. Inclusion of the appropriate solvent molecule into the crystal structure generates supramolecular architectures (2a-d) in which the solvent controlled self-assembly is observed. Spectral properties of these complexes were found to be very important and promising in the area of ytterbium physicochemistry.     

Determination of oxygen in certain gases : Improved winkler method

An improved method is described for the determination of micro-amounts of oxygen gas in argon, carbon dioxide, helium, hydrogen and nitrogen by the Winkler. procedure. The technique is such that a mean standard deviation of ± 0.33 ppm oxygen with a reproducibility of ± 0.67 is obtained for gases varying in oxygen content from 1 to 30 ppm. The results are reproducible on a day-to-day basis. The reagent blank is equivalent to about 2.5 ppm with a deviation of 0.2 ppm. The method can be used for oxygen gas determination from 1 to 1.50 ppm. The accuracy of the method is ± 0.1 ppm for the lower range of oxygen concentrations.The method may also be extended to higher oxygen-containing gases, except that the oxygen determination is made by titration and smaller gas samples are used.     

Potentiometric titration of low concentrations of boric acid anhydride in deuterium oxide and in ordinary water

A precision of 99.5 per cent, or better, is obtainable for the determination of boric acid anhydride (50 to 150 mg per liter) in deuterium oxide or ordinary water solution; titrations may be performed with concentrations as low as 0.76 mg per liter. Sufficient mannitol is added so that the potentiometric curve is duplicable. Glycerol is not satisfactory, in deuterium oxide, at low molar concentrations of boric acid anhydride.Differences in pH end-points for water and deuterium oxide solutions were noted.