Statistische methoden zur ermittlung der verteilung der molekülgrössen in hochpolymeren systemen aus experimentalergebnissen der fraktionierten fällung. IV. Berücksichtigung der polydispersität der fraktionen

The relation between the most important statistical parameters of the number frequency h(P) determining the kinetics of polymerization and the molecular weight distribution H(P) is explained. The polydispersity g_w of H corresponds to the non-uniformity of H(= U). For calculating g_w, a correction formula (22) is derived which takes into account the averaged polydispersity α of the fractions. By this means, the asymmetry of h is also calculated. As explained in an earlier investigation, it is possible to determine the type of distribution function in the SWN step diagram. If this type is known, it is furthermore possible to calculate the correction quantity α according to the equilibrium theory of G. V. Schulz. The α unequivocally depends on the distribution function, the volume quotient φ of the sol and the gel, and on the parameter k of the function type, if the number X of the fractions lies between 5 and 20 and the single fractions show approximately the same mass. As an example, it is shown that then the quantity k, which is characteristic for the type of the reaction, can be calculated from the experimental data with an error of only a few per cent, and α² has a value below 0.1. Although, with a fractionation column, α² generally shows lower values, in favorable cases even down to 0.03, the uncertainty in the determination of the parameter k is, for many practical reasons, generally not lower compared with the uncertainty observed in precipitation fractionations using our new method.     

Über die Chemie der Oberfläche des Titandioxids. III. Reaktionen der basischen Hydroxylgruppen auf der Oberfläche

Adsorption of various acids on anatase of high surface area was studied. Phosphoric, arsenic, sulphuric and acetic acid are specifically adsorbed; hydrochloric and perchloric acid are not adsorbed. Phosphate ions are bound on the TiO₂ surface also from NaH₂PO₄ and Na₂HPO₄ solutions; sodium ions are adsorbed at the same time. OH^? ions on the surface are replaced by anions such as H₂PO in these reactions. The bonding of adsorbed phosphate ions is not purely ionic. Infrared spectra show that adsorbed acetic acid is bound as acetate. NO₂ reacts with the basic OH^? ions undergoing disproportionation; OH^? ions are replaced by NO ions. Phophoric acid adsorption corresponded always to half the total OH population on five different TiO₂ samples. The TiO₂ surface is not completely covered by OH groups. The maximum coverage is ca. 7.5 μMol OH/m².     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. 44. Trialkoxysilylthioderivate der Permethylpolysilane

Contributions to the Chemistry of Silicon-Sulphur Compounds. 44. Trialkoxysilylthio Derivatives of Permethylpolysilanes By reaction of (RO)₃SiSH · NEt₃ (R = i-Pr, t-Bu) with α,ω-Cl₂(SiMe₂)_n (n = 1, 2, 3, 4, 6) or with 1-Cl(SiMe₂)_nMe (n = 2, 4) trialkoxysilylthio derivatives of polysilanes of the two series α,ω-(RO)₃SiS(SiMe₂)_nSSi(OR)₃ and 1-(RO)₃SiS(SiMe₂)_nMe have been prepared. Some properties of obtained new compounds were given. The resistance of the Si? S bond on protolytic splitting has been characterized by half-life times of the alcoholysis reaction.     

Zur Kenntnis der Chemie der Silazane. IV. Über ein Sulfurylphosphazo-silazan

Trichlorophosphazo-sulphurylchloride. Cl₃P?N? SO₂Cl, reacts with heptamethyldisilazane to yield the Si? N? P compound (I) formulated in ?Inhaltsübersicht”?. (I) reacts with PCl₅ or C₆H₅? PCl₄ forming the known 2,2,2,4,4,4-hexachloro-1,3-di-methylcyclo-diphosphazane(II), accompanied by the compound Cl₃P?N? SO₂Cl and C₆H₅? PCl₂?N? SO₂Cl, respectively, which were detected by means of ³¹P-NMR spectroscopy.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXVIII. Trimethylsilylderivate der Trialkoxysilanthiole

Contributions to the Chemistry of Silicon-Sulphur Compounds. XXVIII. Trimethylsilylderivatives of Trialkoxysilanethiols The reactions of trialkoxysilanethiols and their salts with trimethylchlorosilane and hexamethyldisilazane were investigated. The preparation of trimethyltrialkoxydisilthianes has been described. Some properties of the obtained compounds were given and about their silylation ability has been considered.     

Über Chalkogenolate. 146. Asymmetrische Derivate der Kohlensäure mit Elementen der IV. Hauptgruppe. Notiz über Silbermonomethylcarbonat

On Chalcogenolates. 146. Asymmetric Derivatives of Carbonic Acid with main Group IV Elements. Notice of Silver Monomethyl Carbonate The esters of carbonic acid have been prepared by different methods. The compounds were characterized by means of infrared, nuclear magnetic resonance (¹H and ¹³C), and mass spectra. Synthesis and properties of unstable Ag[O₂C? OCH₃] are described. The infrared spectrum is given.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXIII. Die Hydrolysereaktion der Silanthiole

Contributions to the Chemistry of Silicon-Sulphur Compounds. XXIII. The Hydrolysis Reaction of Silanethiols The kinetics of the hydrolysis reaction of silanethiols (RO)₃SiSH and R₃SiSH in dioxane-water solutions were investigated and the rate constants and the activation parameters evaluated. The mechanism of the reaction is discussed. The relationship between the structure of silanethiols and their reactivity are evaluated.     

Über Metall-Stickoxid-Komplexe. XXV. Zur Kenntnis von Nitrosylcyano-Komplexen der Metalle der Eisengruppe

The binuclear nitrosylhalides of iron and cobalt react with cyanide to anionic complexes [M(NO)₂(CN)₂]^? (M = Fe, Co). Substituted monomeric compounds M(NO)₂LBr and Ni(NO)L₂Br lead primarily under replacement of bromide to nonionic complexes M(NO)₂LCN and Ni(NO)L₂CN. In general these complexes react with more cyanide yielding anions [M(NO)₂(CN)₂]^?, [Ni(NO)L(CN)₂]^? and [Ni(NO)(CN)₃]^2?. The paramagnetic dinitrosyliron compounds can be reduced to diamagnetic complexes by Na/Hg. A disproportion reaction of Co(NO)₂P(C₆H₅)₃CN forms a salt [Co(NO)₂ · (P(C₆H₅)₃)₂][Co(NO)₂(CN)₂], a similar salt can be made by the reaction of Na[Co(NO)₂(CN)₂] with [Co(NO)₂(NHP(C₆H₅)₃₂]Br. The IR spectra are discussed.     

Über die Wanderung der Carboxylatgruppe bei der Benzilsäureumlagerung. 26. Mitteilung über Reduktone und Tricarbonylverbindungen

The benzilic acid rearrangement of ethyl α,β-dioxo-butyrate was studied by NMR.-and UV.-techniques. In weak alkaline media (pH < 10) the ester group is hydrolyzed first, then the carboxylate group migrates to form methyltartronate. The migration of the carboxylate group was proved by radioactive labeling. At higher pH-values (pH > 11,5) the intakt ester group migrates, with ester hydrolysis occuring as a second step.     

Über Chalkogenolate. 153. Untersuchungen über Derivate der N-Thioformyldithiocarbamidsäure 3. Ester der N-Thioformyldithiocarbamidsäure und Oxydation von N-Thioformyldithiocarbamaten

On Chalcogenolates. 153. Studies on Derivatives of N-Thioformyl Dithiocarbamic Acid. 3. Esters of N-Thioformyl Dithiocarbamic Acid and Oxidation of N-Thioformyl Dithiocarbamates The esters of N-thioformyl dithiocarbamic acid have been prepared by reaction of tetra-n-butylammonium N-thioformyl dithiocarbamate with the corresponding alkyl iodide. Also the reaction of S-methyl N-formyl dithiocarbamate with Lawesson reagent forms the methyl ester of N-thioformyl dithiocarbamic acid. The oxidation of N-thioformyl dithiocarbamates with iodine yields 1,2,4-dithiazole-3-thione All compounds have been characterized by means of chemical and diverse spectroscopic methods. A new method to prepare 5-phenyl 1,2,4-dithiazole-3-thione is given.