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.     

Stabilitätskonstanten der Kupferkomplexe von Acetessigsäureamiden. I

The stability constants of the copper complexes of acetoacetdialkylamides and substituted acetoacetanilides have been determined by potentiometric pH-measurements. The variation of stability constants with phenyl substituents is interpreted.     

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.     

Belträge zur Chemie der Silicium-Schwefel-Verbindungen. XIV. Reaktion der Silanthiole und cyclo-Disilthiane mit o-Hydroxymercuribenzoesäure

Contributions to the Chemistry of Silicon-Sulphur-Compounds. XIV. Reaction of Silanethiols and cyclo-Disilthianes with o-Hydroxymercuribenzoic Acid. The reaction of trialkoxysilanethiols, di-t-butoxysilanedithiol and tetra-t-butoxy-cyclo-disilthiane with o-hydroxymercuribenzoic acid by means of titration was investigated. By this method some informations about the hydrolytic stability of the Si—S-bound were received.     

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.     

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. 136 [1]. Alkylester der Cyanoameisensäure und der Cyanomonothioameisensäure

On Chalcogenolates. 136. Alkyl Esters of Cyanoformic Acid and of Cyanomonothioformic Acid By use of the phase transfer catalyst 18-crown-6 the esters CH₃O—CO—CN, C₂H₅O—CO—CN, C₂H₅S—CO—CN, and ⁿC₃H₇S—CO—CN have been prepared by reaction of the corresponding chloro compound with potassium cyanide. The prepared compounds have been characterized by means of electron absorption, infrared, nuclear magnetic resonance (¹H and ¹³C), and mass spectra.     

Zur thermodynamisch-phänomenologischen Beschreibung der Färbevorgänge I. Diskontinuierliches Modellsystem

The essential characteristics of a simple, discontinuous model system for mass transfer between two phases are discussed. It is shown that for dyeing processes that conform to this model it is possible, with the aid of the methods of non-equilibrium thermodynamics, to give an unambiguous definition of the concepts «rate of dyeing» and «affinity of dyeing», at any stage of dyeing. It is clear from the derived phenomenological equations that dyeing systems rarely reach a true equilibrium state (i.e. a stationary state of zero order), but that in general an osmotic or a DONNAN equilibrium is attained.     

Über Chalkogenolate. 128. Untersuchungen über Ester der N-Cyancarbamidsäure. 1. Darstellung und Eigenschaften der Ammoniumsalze von N-Cyancarbamidsäureestern und vom N-Methyl-N-cyancarbamidsäureethylester

On Chalcogenolates. 128. Studies on Esters of N-Cyancarbamic Acid. 1. Synthesis and Properties of Ammonium Salts of N-Cyancarbamic Acid Esters and of the Ethyl Ester of N-Methyl N-Cyancarbamic Acid The reaction of NC? N(CO? OR)₂ with NH₃(g) yields NH₄[NC? N? CO? OR], where R = CH₃, C₂H₅, and C₆H₅. NH₄[NC? N? CO? OC₂H₅] reacts with H₃CI to form NC? N(CH₃)? CO? OC₂H₅. The called compounds have been studied with chemical and spectroscopic methods.     

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.     

Metallkomplexe der Phosphinsäuren. XVIII. Ansa- und Oligokomplexe bifunktioneller Dithiophosphinsäuren

Metal Complexes of Phosphinic Acids. XVIII. Ansa- and Oligo-Complexes of Bifunctional Dithiophosphinic Acids The influence of R′ in the bifunctionell chelate ligands ^?S(S)P(R)? R′? (R)P(S)S^? on the association of their planar Ni^II and tetrahedral Co^II complexes is investigated by vapour pressure osmometry and in the case of diamagnetic Ni^II compounds also by ³¹P-NMR spectroscopy. While insoluble coordination polymers [S₂P(R)? R′? (R)PS₂M]_x (M = Ni^II, Co^II) are formed with R′ = p-(C₂H₄)₂C₆H₄ it can be shown, that in solutions of the complexes with R′ = o-(C₂H₄)₂C₆H₄ and R′ = o-(C₃H₆)₂C₆H₄ there exists an association equilibrium comprehending oligomers with n ? x. Above all in the latter case steric conditions seem to favour intramolecular chelating and thus formation of ansa-type complexes. Synthesis of the ligands and the complexes is described.     

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.     

Einfluss der geometrischen verhältnisse der trägermaterialien auf die leistungsfähigkeit eines extraktions-chromatographischen systems II. Änderung der austauschkinetik des Eu im system HDEHP--- SiO2---HCl in abhängigkeit von der porengrösse der träger-materialien (matrizen)

The kinetics of europium exchange were studied aa a function of the pore size of the solid support with the HDEHP---HCl partition chromatography system. Spherical silica gel paarticles with an average diameter of 56 μm were investigated and found to have surfaces between 1 and 195 m²/g aand the median pore diameter in the range of 117–5,500 Å. The coating of the silylated support material was 10% by weight.The kinetics of the europium exchange were found to be a heterogenous, transport-controlled reaction in the aqueous phase. The unsteady exchange is described by Fick's second law. The transportation of the HDEHP-molecules from the interface into the aqueous phase must be considered to be rate-determining step. Its length (= distance between the interface and the layer where the complex ion is formed) as well as the variable hindrance due to different pore size of this rate-determining step was investigated.Four pore size ranges were discussed, in each of which the transport reaction is hindered to a greater or smaller extent. Thus we could demonstrate that in the case of a pore size range with pore diameter > 2 μm the rate of exchange with increasing coating of the solid support with HDEHP could be explained in the light of the above results due to the influence of the HDEHP-solubility in the aqueous phase.

Zusammenfassung

Es wurde die Kinetik des Europiumaustausches in dem extraktionschromatographischen System HDEHP---HCl in Abhängigkeit von den geometrischen Kenndaten der Trägermaterialien (Matrizen) untersucht. Als Trägermaterialien dienten kugelförmige Kieselgele mit einem mittleren Korndurchmesser von 56 μm. Die Oberflächen der verschiedenen, vermessenen Präparate lagen zwischen 1 und 295 m²/g, der häufigste Porendurchmesser im Bereich von 117–5500 Å. Die Belegung der silikonisierten Matrizen mit HDEHP betrug einheitlich 10 Gew. %.Die Kinetik des Europiumaustausches wurde als heterogene, transportlimitierte Reaktion in der wässrigen Phase erkannt. Der instationäre Austausch wird mit dem zweiten Fick'schen Gesetz beschrieben. Als geschwindigkeitsbestimmender Schritt muss der Transport der HDEHP-Moleküle von der Grenzfläche in die wässerige Phase betrachtet werden. Für diesen geschwindigkeitsbestimmenden Transportschritt wurde sowohl seine Länge (= Abstand Phasengrenzfläche—Reaktionsebene, in der die Komplexierung des Europiums stattfindet) als auch seine unterschiedliche Behinderung bei verschiedenem Porendurchmesser behandelt. Es werden vier Porengrössenbereiche diskutiert, bei denen sich eine unterschiedlich starke Behinderung dieses Transportvorganges feststellen lässt. Dabei konnte für einen Porengrössenbereich (Porendurchmesser > 2 μm) die Übereinstimmung der Austauschgeschwindigkeit mit der des analogen Extraktionssystems nachgewiesen werden. Die Änderung der Austauschgeschwindigkeit mit zunehmender HDEHP-Belegung der Matrizen konnte unter Berücksichtigung der vorliegenden Ergebnisse über den Einfluss der HDEHP-Löslichkeit in der wässrigen Phase erklärt werden.     

Perfluoralkylierte Säuren des Phosphors. II. Zur Kenntnis der Trifluormethyl-benzol-phosphinsäure

Perfluoroalkylated Acids of Phosphorus. II. On Trifluoromethyl Benzene Phosphinic Acid Bis-(trifluoromethyl-benzene) phosphinic acid anhydride 1 , easily formed by CF₃COOH and C₆H₅PCl₂, yields on reaction with aqueous Na₂CO₃ solution the sodium salt of trifluoromethyl benzene phosphinic acid 2 . The acid itself is isolated by ion exchange as a hygroscopic and highly acidic substance.     

Photochemische Reaktionen. 74. Mitteilung. Notiz zur Photoreaktivität ausgewählter ungesättigter Ketoalkohole der Jononreihe

UV.-irradiation (λ = 254 nm) of the hydroxy-enones 3 and 6 in acetonitrile results in the cyclization to the unstable isomeric allylic alcohols 4 and 7 , which dehydrate easily to the isolated unsaturated ether 5 and 8 . The racemic γ,δ-dihydroxy-enone 9 upon irradiation under the same conditions gives rise to the exclusive formation of the furane-compound 11 .