Structure and phase behaviour of the ternary system water, n-heptane and the nonionic surfactant Igepal® CA520

The phase behavior of the system water, n-heptane and the nonionic surfactant Igepal^® CA520 has been studied by visual inspection, high-performance liquid chromatography, polarizing microscopy and freeze-fracture electron microscopy. The phase diagram at 25?°C contains two large homogeneous microemulsion phases, an extended region of a lamellar liquid crystalline structure and some two- and three-phase regions. The oil-rich part of the phase diagram has been investigated by static and dynamic light scattering in order to examine the behavior of the collective diffusion coefficient and the scattering intensity in the presence of increasing concentrations of water, starting from the binary system of n-heptane and Igepal^® CA520. The results suggested that at a very low water content the aggregates of the microemulsion are small. With the exception of this region the structure is bicontinuous.     

Synthese,Struktur und Thermolyse von NH4[Re3Br10]

Synthesis, Structure and Thermolysis of NH₄[Re₃Br₁₀] NH₄[Re₃Br₁₀] crystallizes as dark brown single crystals upon slow cooling of a hot, saturated hydrobromic-acid solution of [Re₃Br₉(H₂O)₂] after the addition of NH₄Br. The crystal structure (monoclinic, C2/m (Nr. 12); Z = 4; a = 1461.6(7), b = 1 085.6(4), c = 1030.3(7) pm, β = 92.63(4)°, V_m = 245.9(4)cm³/mol; R = 0.097, R_w = 0.043) contains [Re₃Br₁₂]^? units that share two common edges. These chains run along [010] and are held together by NH₄⁺ ions. Each NH₄⁺ is surrounded by eight Br^? from four different chains. The first step of the thermal decomposition at 290°C is the disproportionation to ReBr₃ (ReCl₃ type), rhenium metal and (NH₄)₂[ReBr₆]. Secondly, the internal reduction of (NH₄)₂[ReBr₆] at 390°C to rhenium metal takes place.     

Quaternary ammonium and sulfonium derivatives of 2-chloromethylbutadiene and poly-2-chloromethylbutadiene

2-Chloromethylbutadiene has been converted to quaternary ammonium and sulfonium monomers which have been polymerized at room temperature. They show a very great tendency to dimerize on heating in water solution. The aqueous quaternary monomer dimerized 25 times as fast as the aqueous sulfonium monomer and nearly 10⁵ times as fast as neat isoprene at 50°C. The quaternary monomer dimerized with itself in a water solution to which 2-hydroxymethylbutadiene has been added as an example of a nonionic diene. The latter monomer did not dimerize rapidly in water, nor did 2-aminomethylbutadiene. The hydrochlorides of 2-aminomethylbutadiene and 2-dimethylaminomethylbutadiene dimerized at rates comparable to that of the sulfonium monomer. Poly 2-chloromethylbutadiene contains reactive chlorine except for the structure resulting from the minor extent of 1,2 addition. Water-soluble derivatives have been made from it with nucleophilic tertiary amines and sulfides. Cationic polymers are substantive to paper pulp, and the sulfonium polymers can be cured in paper to give improved wet strength.     

Die Elektronische Struktur von Nb3Br8

The Electronic Structure of Nb₃Br₈ The bonding in Nb₃Br₈ was investigated with the aid of extended Hückel and molecular orbital calculations to gain some understanding concerning stability and possible chemical altering. Seven electrons occupy metal—metal bonding states of a Nb₃Br₈ unit. Six of them are responsible for strong σ bonds within the Nb₃ cluster. One to two additional electrons may be incorporated to occupy a₁ orbitals, which slightly increase the bonding in a Nb₃ cluster, rather than between adjacent clusters.     

Untersuchungen zur thermischen Zersetzung der Ammoniumyttriumhalogenide III. Ammoniumyttriumbromid, (NH4)3YBr6

Investigation on the Thermal Decomposition of Ammonium Yttrium Halides. III. Ammonium Yttrium Bromide, (NH₄)₃YBr₆ The decomposition equilibria of NH₄Br and (NH₄)₃YBr₆ were determined by total pressure measurements. It was shown by high temperature X-ray patterns and DTA that (NH₄)₃YBr₆ and YBr₃ show phase transitions in the measured temperature region. An endothermic transition of YBr₃ starts near 300°C and is very slow. By interpretation of the thermal decomposition of (NH₄)₃YBr₆, the enthalpy of formation, and the standard entropy was derived. In the system NH₄Br/YBr₃ only the described phase (NH₄)₃YBr₆ exists.     

Literatur

Analytical and Bioanalytical Chemistry -