Photooxidation von Leukofarbstoffen. XII. Kurzzeitspektroskopische Untersuchungen zur Photooxidation von Bis-schwefelsäuremonoestern der Leukoformen von Thioindigoverbindungen

Photooxidation of Leuco Dyes. XII. Time Resolved Investigations on the Photooxidation of Bis-sulfuric Acid Monoesters of Leucothioindigoid Compounds The photooxidation of 4, 4′-dimethyl-6, 6′-dichlorothioindigosol ( 1 ) was studied by means of laser and conventional flash photolysis. Three transients were detected and assigned to a radical R generated by homolytic splitting of one O S-bond of the parent compound and to two further radicals which are formed from R by hydrolytic cleavage of the second ester group. The latter two radicals are in a protolytic equilibrium with each other and react, depending on the nature of the solvent by H-atom abstraction, or by disproportionation forming the leuco-thioindigoid dye or both dye and leuco dye. A mechanistic scheme is proposed.     

Photooxidation von Leukofarbstoffen. VIII. Kurzzeitspektroskopische Untersuchungen zum Mechanismus der Photooxidation von Leukokristallviolett

Photooxidation of Leuco Dyes. VIII. Time Resolved Investigations of the Mechanism of the Photooxidation of Leucocrystal Violet The photooxidation of leucocrystal violet has been reexamined by means of conventional and laser flash photolysis as well as spin trap experiments. Three radical transients have been observed and assigned to the cation radical (λ_max ≈ 490, 530 nm), the neutral radical with one NCH₃ CH₂ moiety (λ_max ≈ 480 nm) and the triphenyl methyl radical derivative (λmax ≈ 400 nm).     

Photooxidation von Leukofarbstoffen. III. Sensibilisierte Photooxidation von Leukofluoreszein

Photooxidation of Leuco Dyes. III. Sensitized Photooxidation of Leuco Fluorescein Quantum yields of the sensitized photooxidation of leuco fluorescein are reported. Fluorescein and benzophenone were found to be efficient sensitizers of photooxidation of leuco fluorescein. There is a characteristic dependence of quantum yields on concentration of leuco fluorescein and oxygen in the solution. The results are discussed on the basis of reaction scheme proposed for the sensitized formation of fluorescein.     

Untersuchungen zur Sensibilisierten Photooxidation von 1,3-Dithiolthionen-(2)

Studies on the Sensitized Photooxidation of 1,3-Dithiol-thiones-(2) 1,3-Dithiol-thiones-(2) 1a — h are sensitized photooxidable. With methylenblue as a sensitizer it is probable that singlet oxygen becomes the oxidizing reagent. The rate of oxidation increases with the capacity of the substituents of 1 to increase the electron-density in the heterocycle. As main products of the photooxidation of 4,5-diphenyl-1,3-dithiol-thone-(2) 1a 4,5-diphenyl-1,3-dithiolone-(2) 8 , dibenzoylsulfid 9 , and benzil 10 are isolated beside carbondisulfide, sulfur and sulfurdioxid. The 1,3-dithiolone-(2) 8 reacts with singlet oxygen too. A way of forming the reaction products is discussed.     

Untersuchungen zur struktur von emulsions-polyvinylchlorid

The structural characteristics of PVC prepared by bulk or suspension polymerization as well as their relationships to synthesis and processing conditions have repeatedly been investigated. Thus, grains aggregates, particles, domains and microdomains have to be discerned according to Geil. In our electron microscope studies emulsion PVC powder obtained by spray drying of aqueous PVC latices and used in preparing pastes were investigated. The grain structure was found to change in preparing pastes and subsequent gelation. With increasing temperature of gelation the grains disintegrate, particles arrange in dense packings and, finally, loose their individuality. Due to diffusion of the plastiziser the particles acquire distinctly discernible microdomain structures. Microdomains are found to be the dominating structural characteristic of PVC gelation products.     

Untersuchungen zur Photolyse von Diaryliodoniumsalzen

Investigations on Photolysis of Diaryliodonium Salts The photolysis of diaryliodonium salts in solution leads to various competitive and consecutive reactions. Upon irradiation, the excited state desactivates mainly through homolytic cleavage of the C I-bond, but to a minor extent also through heterolytic cleavage of the same bond. Thus, several photolysis products have been obtained: aromatics, new iodonium salts, iodoaromatics, substitution products of the solvent, protonic acid in aqueous solutions, iodide and iodate ions and iodine. In the case of diphenyliodonium iodide the yields of iodine are higher compared to those of other salts because of electron transfer processes. The quantum yields of the disappearance of the iodonium salt (Φ_I) and of the formation of protonic acids (Φ_P) are equal within the experimental error. These values do not depend on the nature of the solvent, with the exception of H-donor solvents, on the initial salt concentration and on oxygen. But, they depend strongly on the light intensity and on the substituent at the aromatic ring. The Φ_P-data also depend on the oxidation potential of the anion used. For diphenyliodonium chloride, the quantum yield of iodobenzene formation reaches only the half of the values for Φ_I and Φ_P. A kinetic scheme is given for the explanation of the light intensity dependence, which is based on 1. and 2. order reactions of intermediates formed by the homolytic pathway. It is assumed, that the electron transfer reaction by iodide salts proceeds only between the iodide ion and the intermediate products.     

Untersuchungen zur Sensibilisierung von Azofarbstoff-Perhalogenid-Systemen

Investigations Concerning Sensitization of Silver Free Information Recording Materials with Azo Dyes and Polyhalogen Compounds Recording materials mentioned in the title are sensitive to the visible region of light. The reason therefore is an energy transfer from the azo dye to the polyhalogen compounds, preferentially CBr₄. It's possible to separate the absorption spectra of azo compounds used in this work into two gaussian functions, which relates to n,π*- and π,π*-transitions. Only the excitation of the n,π*-transition causes sensitization. A mechanisms of sensitization is proposed.     

Untersuchungen zur Sulfochlorierung von Paraffinen. VI. Untersuchungen über die Sulfochlorierung von definierten Alkylchloriden

Studies on Sulphochlorination of Paraffins. VI. Studies on the Sulphochlorination of Individual Alkyl Chlorides The products of sulphochlorination of individual C₂–C₇ alkyl chlorides were studied by means of ¹H- and ¹³C-n.m.r. spectroscopy. Gaschromatographic determination of the isomers formed was possible after the reaction of the chloroalkane sulphochloride mixture with dimethyl amine in ether. In no case geminal chloroalkane sulphochlorides were formed. Vicinal chlorosulphochlorides are formed, but substitution in greater distance from the chlorine is preferred if possible. Thus higher alkyl chlorides yield only very little amounts of vicinal chloroalkane sulphochlorides. The relative rates of sulphochlorination of alkyl chlorides were determined by competitive reactions.     

Untersuchungen zur Sulfochlorierung von Paraffinen. VII. Untersuchungen über die Chlorierung von definierten Alkansulfochloriden

Studies on Sulphochlorination of Paraffins. VII. Studies on the Chlorination of Individual Alkane Sulphochlorides The products of the chlorination of individual C₂–C₆ alkane sulphochlorides were studied by means of ¹³C-n.m.r. spectroscopy. In no case a geminal chloro sulphochloride could be found, and only in very few cases chlorination at vicinal C H-bonds took place. As in the sulphochlorination of alkane sulphochlorides the C H-bonds geminal and vicinal to the sulphochloride group are strongly descativated. The results of ¹³C-n.m.r. analyses were confirmed by the results of gaschromatography of the sulphonic acid dimethyl amides, formed by the reaction of the chlorination mixtures with dimethyl amine.     

Vergleichende Untersuchungen zur Arylaminierung von Benzofuroxan-Derivaten

Comparative Studies on Arylamination of Benzofuroxan Derivatives The amination of benzofuroxan 2a and monosubstituted benzofuroxans 2b – e with alkali metal salts of formanilides 1 and sodium acetanilides 6 is described. Thus, the reaction of 2a with 6a – d gives the benzotriazole 1-oxides 3a – d . The benzofuroxans 2b and 2c react with sodium formanilides to give the isomeric mixtures 3f / 3g and 3h / 3i . Potassium 4-nitroformanilide reduces 2a furnishing benzofurazan 7 . Nitrobubstituted benzofuroxans such as 2d and 2e undergo a carbocyclic amination leading to the benzofurazans 8 and 9 .     

Kinetische Untersuchungen zur Pyrolyse von Mono-n-alkyl-cyclohexanen

Kinetic Investigations of the Pyrolysis of Mono-n-alkyl-cyclohexanes The thermal decomposition of cyclohexane and six mono-n-alkylcyclohexanes was studied kinetically in a metallic laboratory tubular reactor at 650 to 850°C and atmospheric pressure. Kinetic parameters were found to be a function of length of the alkylic side chain. A comparison with analogous parameters of n-paraffins and the unsubstituted cyclohexane allowed the conclusion that C C-scission in the alkylic chain is the initial reaction in pyrolysis of n-alkylcyclohexanes followed by radical attacks to all C H-bonds of the feed molecules.