Fourier transform IR spectroscopic observation of chlorine nitrite,ciono, formed via Cl + NO2 (+M) → ClONO(+M)

Using the FTIR method, chlorine nitrite (ClONO) and nitryl chloride (ClNO₂) were identified as reaction products in the photolysis of Cl₂-NO₂ mixtures. The observed yields of ClONO (? 80%) and ClNO₂ (? 20%) suggest that Cl atom adds mainly to the O atom rather than the N atom of NO₂ molecule.     

FTIR studies of the kinetics and mechanism for the reaction of Cl atom with formylchloride

The rate constant for the reaction Cl + CHClO → HCl + CClO was determined from relative decay rates of CHClO and CH₃Cl inthe photolysis of mixtures containing Cl₂ (～1 torr), CH₃Cl (～1 torr), and O₂ (～0.1 torr) in 700 torr N₂. In such mixtures CHClO was generated in situ as a principal product prior to complete consumption of O₂. The value of k(Cl + CHClO)/k(Cl + CH₃Cl) = 1.6 ± 0.2(3σ) combined with the literature value of k(Cl + CH₃Cl) = 4.9 × 10^?13 cm³/molecule sec gives k(Cl + CHClO) = 7.8 × 10^?13 cm³/molecule sec at 298 ± 2 K, in excellent agreement with a previous value of (7.9 ± 1.5) × 10^?13 cm³/molecule sec determined by Sanhueza and Heicklen [J. Phys. Chem., 79 , 7 (1975)]. Thus this reaction is approximately 100 times slower than the corresponding reactions of aldehydes and alkanes with comparable C? H bond energies (≤95 kcal/mol).     

Fourier transform IR spectroscopic observation of pernitric acid formed via HOO + NO2 → HOONO2

Kinetic and spectroscopic evidence has been found for the formation of pernitric acid via HOO + NO₂ → HOONO₂ using Cl-atom sensitized oxidation of H₂  NO₂ mixture and a Fourier transform IR spectroscopic detection method.     

Zur wechselseitigen Löslichkeitsbeeinflussung von Polymeren mit verschiedenen Molekulargewichten, 2. Mitt.: Mischlösungsmittel mit präferentieller Fällungsmitteladsorption durch das Polymere

Zusammenfassung Für das System CHCl₃/Aceton/Polystyrol wurde die Trübungskurve einer Mischung aus gleichen Gewichtsteilen zweier Polystyrole mit verschiedenen Molekulargewichten mit den Trübungskurven der Komponenten verglichen.Das untersuchte Mischlösungsmittel, aus dem die Fällungsmittelkomponente bevorzugt ins Polymerknäuel aufgenommen wird, zeigt eine ähnliche wechselseitige Löslichkeitsbeeinflussung der Polymeren wie das Cyclohexan — Polystyrolsystem (Einkomponentenlösungsmittel). Der Temperaturbereich, über den sich die Trübungskurve erstreckt, nimmt mit steigender Uneinheitlichkeit der Polymeren stark zu. Die Änderung im Typ der Trübungskurve, verglichen mit Einkomponentenlösungsmitteln (Abnahme der Trübungstemperatur für die untersuchten polymolekularen Proben mit steigender Polymerkonzentration über den gesamten Bereich), wird zurückgeführt auf die Änderung der effektiven Lösungsmittelgüte mit der Polymerkonzentration.Für die untersuchte Probe mit wahrscheinlichster Molekulargewichtsverteilung fällt der kritische Punkt mit dem Wendepunkt der Trübungskurve zusammen.Aus den gemessenen kritischen Konzentrationen können auf der Grundlage derFlory-Huggins-Theorie keine physikalisch sinnvollen Wechselwirkungsparameter berechnet werden; dieser Befund wird auf die Nichtberücksichtigung des Struktureffekts durch die obige Theorie zurückgeführt.

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Mutual influence of polymers of different molecular weights on solubility, II: Mixed solvent systems with preferential adsorption of precipitant by the polymer

The cloud-point curve for a solution containing equal amounts of two polystyrene samples of different molecular weight has been compared with the cloud-point curves of the components for the system CHCl₃/acetone/polystyrene. In the mixed solvent under investigation the non-solvent is preferentially adsorbed into the interior of the polymer coil. As far as the mutual influence of the polymers on the solubility is concerned the system behaves like the single solvent system cyclohexane-polystyrene. The temperature range covered by the cloud-point curve on the other hand strongly increases with the non-uniformity of the polymer. The variation of the type of the cloud-point curve as compared with single solvents (decrease in the precipitation temperature with increasing polymer concentration over the entire range in the case of the polymolecular samples studied) is explained by the variation of the effective solvent power with the polymer concentration.For the sample with a most probable molecular weight distribution the critical point coincides with the inflection point of the cloud-point curve. The evaluation of physically significant pair interaction constants from the measured critical concentrations on the basis of theFlory-Huggins theory is not possible; this finding is explained by the fact, that also a structure effect has to be considered.

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Mit 3 Abbildungen     

Das Diels-Alder-Zwischenprodukt als Kettenübertragungsmittel bei der spontanen Styrol-Polymerisation. 1. Mitt. Ein neuer Nachweis aus der kinetischen Analyse der photoiniierten Polymerisation

Ohne Zusammenfassung     

Die Polymerisation von N-Vinylcarbazol in Gegenwart von Tetrabromkohlenstoff, 1. Mitt.: Der Einfluß von langwelligem UV

N-Vinylcarbazol (NVC) shows an extremely fast polymerization when irradiated for several minutes in a glass vessel at 30°C with long wave length UV in benzene solutions containing CBr₄. The conversion-time curves are sigmoid in character. The polymerization continues with its rate practically unchanged when the irradiation is stopped. Therefore termination reactions must be absent in this polymerization process which is shown to be cationic in mechanism. When a solution of CBr₄ in benzene is irradiated and the monomer is added after the irradiation has been stopped polymerization occurs likewise; its rate, however, is two orders of magnitude less than the maximum rates in the direct polymerization in the presence of CBr₄ and light. Here the conversion-time curves are linear. In both cases acidic products can be detected in the reaction systems. A reaction scheme is developed which attributes the initiation of polymerization by preirradiated CBr₄ solutions to the action of acidic decomposition products of CBr₄ (HBr). In the direct photopolymerization the monomer, probably in form of itsEDA-complex with CBr₄, participates in the initiation step or at least in the uptake of the photochemical energy, leading to a photochemically induced cationic polymerization. Based on this scheme an interpretation of the experimental results is given.