The photodegradation of poly(vinyl chloride)—V The effect of wavelength of irradiation on the dehydrochlorination reaction

For a purified sample of poly(vinyl chloride), it is found that radiation of wavelength less than 300 nm causes dehydrochlorination. It appears that polychromatic radiation yields a constant ratio of concentrations of polyenes, even from the very early stages of reaction. It is proposed that energy transfer is an important step in the photodecomposition of poly(vinyl chloride).     

Stochastic description of a reaction scheme with autocatalysis and saturation law

We apply the master equation and non-linear Fokker-Planck techniques to a model with autocatalysis and (Michaelis-Menten, Langmuir-Hinshelwood) saturation law and the minimal set of reactive steps for a well posed problem is given.     

Polyselenide mit langkettigen Tetraalkylammoniumionen Die Kristallstruktur von Trimethyl-tetradecyl-ammonium-hexaselenid

Polyselenides with Long-chain Tetraalkylammonium Ions. Crystal Structure of Trimethyltetradecyl-ammonium Hexaselenide Na₂Se₂ and Na₂Se react with various tetraalkylammonium halides in ethanol and in presence of grey selenium and catalytic quantities of iodine forming different polyselenides Se_n^2? (n = 3, 5—9). In the solutions equilibria of polyselenides seem to occur; cooling of saturated solutions causes crystallization of polyselenides with a composition depending on the cation. Tri- and pentaselenide are dark green. The higher members form black crystals, all compounds are sensitive to oxygen. The i.r. spectra are reported. [(CH₃)₃N(CH₂)₁₃CH₃]₂Se₆ is characterized by a crystallographic structure determination with X-ray data: space group P2₁2₁2, Z = 4, a = 5043, b = 734.2, c = 600.3 pm (986 observed independent reflexions. R = 0.072). The compound consists of trimethyl tetradecylammonium ions and angular Se₆^2? chains of symmetry C₂ with Se? Se bond lengths of 227 and 235 pm.     

Zur Struktur von N-Benzoylthiobenzamid

Structure of N-Benzoylthiobenzamide N-Benzoylthiobenzamide forms two polymorphic modifications of which the crystal and molecular structures have been determined by X-ray structure analysis. In both modifications the molecules exist as NH tautomeres, but there are differences with regard to their rotameric configurations. In the monoclinic modification both symmetry independent molecules have a Z,Z′ configuration. The triclinic modification also contains two symmetry independent molecules, but now a Z,Z′ and an E,Z′ configuration exist. All four molecules deviate appreciably from planarity. The results of both structure determinations are compared with each other and with the structure of monothiodibenzoylmethane.     

Colloidal interactions: contact limiting laws,double-layer dissociation,and "non-DLVO" (Derjaguin–Landau–Verwey–Overbeek) forces

The conceptual basis and main results of a new model of the dissociative electrical double layer augmented with Lubetkin-Middleton-Ottewill (LMO) dissociative law are summarized. The main results are: the derivation of fundamental limiting laws of planar repulsions in the limit of surface contact, and their transition to the Debye-Hückel limiting laws at infinite separation; the prediction of stronger and longer-range electrostatic forces, quantitatively and consistently accounting for repulsions in colloidal montmorillonites; the discovery of the classical Debye-Hückel interionic effect being operative in increasing double-layer dissociation by lowering the activities of diffuse ions via the LMO law; the prediction of maxima of Stern potentials in spherical symmetry without any further assumptions, and the prediction of no maxima for platelike montmorillonites. In the light of these new insights, the concepts of "hydration forces" and other close-range "non-DLVO" forces may need to be revised, as well as the origin of the maxima of electrophoretic mobilities (Stern potentials) for spherical colloids.     

Thermal and dynamic analysis of the reactions between formic acid and triethylamine

It is possible to study the problems of thermal regulation and energy storage by utilizing chemical reactions. For this purpose, a method of dynamic and global modelling is used to determine the enthalpy of reaction of formic acid and triethylamine.     

N2O decomposition over Fe/ZSM-5: reversible generation of highly active cationic Fe species

Fe-oxide species in Fe/ZSM-5 (prepared by chemical vapor deposition of FeCl3)--active in N2O decomposition--react with zeolite protons during high temperature calcination to give highly active cationic Fe species, this transformation being reversible upon exposure to water vapor at lower temperature.     

Temperature induced structural changes of Cu(II) and Ni(II) complexes and their thermal decomposition

The paper discusses the structural changes of some Cu(II) and Ni(II) complexes during the heating and their influence upon the decomposition stoichiometry. The influence of the interactions inside of coordination polyhedra, bonding and stereochemical properties of the counter ions or molecules are discussed in this connection as well. The expressive influence of the plasticity or rigidity of the Cu(II) and Ni(II) coordination polyhedra, respectively, is emphasized.

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Zusammenfassung Es werden wÄrmebedingte StrukturverÄnderungen einiger Cu(II) bzw. Ni(II)-Komplexe sowie deren Einflu\ auf die Stöchiometrie der Zersetzung beschrieben. In diesem Zusammenhang wird auch ebenso der Einflu\ von Wechselwirkungen innerhalb des Koordinationspolyeders sowie von Bindungs- und stereochemischen Eigenschaften der Gegenionen oder -moleküle beleuchtet. Es wird der ausdrucksvolle Einflu\ der PlastizitÄt und HÄrte von Cu(II)- und Ni(II)-Koordinationspolyedern hervorgehoben.