Die Jodierung von desaktivierten aromatischen Aminen in wässeriger Phase

By treatment of deactivated aromatic amines such as 4-nitroaniline, 4-aminobenzonitrile or 2-bromo-4-nitro-aniline with iodine in water at 90–93° for 30–35 hours, in the presence of hydrogen peroxide, monoiodinated products with over 99% purity are obtained in 88–98% yield.     

Beitrag zur Kinetik der Korrosion von Eisen in konzentrierter Schwefels?ure

Ohne Zusammenfassung     

Beitrag zur Kinetik der Korrosion von Eisen in konzentrierter Schwefelsäure

Ohne Zusammenfassung     

Der Gegenionen-Effekt bei der durch Perchlorsäure initiierten Polymerisation von Styrol

The effect of various counter-ions has been investigated in the cationic polymerisation of styrene in 1,2-dichloroethane at different temperatures (238 K, 253 K). The soluble silver salts of the corresponding acids HBF₄, HClO₄, HPF₆, HAsF₆, and HSbF₆ were added to the reaction medium before initiation by perchlorid acid. Monomer consumption is seen to be incomplete under these circumstances. Initial polymerisation rates and the final degree of monomer conversion rise with decreasing nucleophilicity of the counter-ions.A kinetic scheme is proposed which is able to describe the course of polymerisation and gives the approximate values of the rate constants for propagation, termination and chain transfer reactions, respectively. The information obtained from GPC-measurements on the polymeric products supports the view that chain propagation takes place by at least two different forms of active species, the ratio of which is strongly determined by the nature of the added silver salt.

     

Die Komplexbildung der neutralen Amidgruppe mit Cu2+ in wässeriger Lösung

The interaction between Cu²⁺ and the terdentate ligands N-picolinoyl-ethylenediamine, glycine-2-pyridylmethylamide, N^α-(2-pyridylmethyl)-glycinamide and N^α-(2-pyridylmethyl)-glycine-ethylamide, respectively, has been studied by spectrophotometry and potentiometry. At high pH values the ionised amide group undergoes complex formation and the resulting chelates have similar structures and stabilities. In slightly acidic solution however, each ligand gives rise to a different species. These facts are explained by assuming that the neutral amide group coordinates through its carbonyl oxygen atom. The stability constant and the absorption spectrum of each complex have been calculated by computer programmes.     

Die Komplexbildungstendenz des dreiwertigen Antimons in wässeriger Lösung

The formation of the complexes of trivalent antimony ion with the following ligands has been investigated with pH measurements: D -tartaric acid, L -tartaric acid, catechol, catechol-3,5-disulfonic acid, 2,3-dihydroxybenzoic acid, mercaptoacetic acid, rac-thiomalic acid, meso-, rac-dithiotartaric acid, and mercapto-ethanol. Using the determined equilibrium constants, a classification of the ligands with respect to their ability to sequester the cation studied is given. In a discussion in which data of the literature are also included the structure of the tartar emetic, the possibility of a volumetric determination of the antimony, some problems concerning the coordination number, and the structure of the complexes are examined.     

Über Veränderungen der Mikrostruktur während der Hydratation von Monocalciumaluminat bei 50°C

On the Change of Microstructure During the Hydration of Mono Calcium Aluminate at 50°C The course of hydration of mono calcium aluminate at 50°C is characterized by periods of different reaction rates. Measuring the change of specific surface area, heat evolution, degree of hydration and by chemical analysis of the liquid phase it is shown that this behaviour has to be attributed to the formation of a primary reaction layer on the surface of the CaO · Al₂O₃ in the first stage of hydration. At later times, due to conversion and crystallization processes, the reaction rate is influenced by changes of the microstructure of the shell of hydration products covering the CaO · Al₂O₃ grains.     

Synthese von phenoxygruppenhaltigen Derivaten der Methandiphosphonsäure

Synthesis of Phenoxy Derivatives of Methanediphosphonic Acid Derivatives of the methanediphosphonic acid containing different numbers of phenoxy groups were prepared by Michaelis-Arbusov reaction of iodomethane phosphonic acid esters with phosphorous acid esters and by reaction of methane diphosphonic acid tetrachlorid with sodium phenolate. The obtained products were investigated by means of n.m.r. spectroscopy.     

Oxydation von nichtcyclischen Derivaten der Methylarsonigsäure

Oxidation of Noncyclic Derivatives of Methylarsonous Acid Reaction of methyldichloroarsine with alcohols and sec. amides yields esters, diamides and amidechlorides of methylarsonous acid. Oxidation with o-chloranil yields the corresponding derivatives of methylarsonic acid.     

Die gaschromatographische Trennung der Methylester von 4-Chlorphenoxyessigs?ure, 2,4-Dichlorphenoxyessigs?ure und 2,4,5-Trichlorphenoxyessigs?ure

Ohne Zusammenfassung     

Die Verwendung von Perchlors?ure bei der Analyse von Treibmitteln

Ohne Zusammenfassung     

Die Komplexe der Hexamine «penten» und «ptetraen» Thermodynamik ihrer Bildung in wässeriger Lösung

The two hexamines (H₂N? CH₂? CH_{2? )2}N? (CH_2)n? N(? CH₂? CH₂? NH₂₎₂, «penten» (n = 2) and «ptetraen» (n=3) have been investigated as chelating agents for COIII (preparative Study) and some of the divalent metal ions (potentiometric and calorimetric studies). Both amines function as sexadentate ligands for Co^III, Co^II and Ni^II, but one of the terminal aminogroups is much easier detached from the metal in case of M (penten)^v+ than in case of M(ptetraen)^v+, thus revealing more strain in the fivemembered chelate rings of the girdle plane of the «penten» complexes. On the other hand, the sixmembered chelate ring in M(ptetraen)^v+ is more strained than the five-membered ring comprising the tertiary nitrogen atoms of M(penten)^v+ Cu^II and Zn^II coordinate with both ligands only 5 of the 6 basic nitrogen atoms present. Both hexaamines function as sexadentates again with Mn^II, but the metal is coordinated with a molecule of water in addition to the 6 nitrogen atoms in the «penten» complex in contrast to the «ptetraen» complex. The thermodynamic functions for the protonation of the hexamines and for the addition of metal ions in aqueous solution are understood in almost every detail. The dielectric shielding of the charges of the reactants exerted by the solvent has to be taken into account; it is reduced by electrostriction as well as by an increase in temperature. It is shown that the approach of charges of equal sign often is an exothermic process.