Untersuchungen über die emulgierende Wirkung von Natriumcholeat

Toluene-in-water emulsions were prepared using sodium choleate as emulgent. The microscopic data revealed the systems flocculating at appreciable rate on ageing and with electrolyte content. Half lives of the dispersions for different concentration of flocculants were determined. The electrophoretic results and the calculated energy data showed the emulsion with high degree of stability. The reversible flocculation occurring in secondary minima is thus concluded. Adsorption constants and free energy of adsorption etc. at isoelectric point were calculated.

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Mit 4 Abbildungen     

Metal complexes of hybrid oxygen — arsenic ligands. Part I. Complexes ofo-dialkyl/arylarsinobenzoic acids with chromium(III)

Summary Reactions of hybrid oxygen-arsenic ligands:o-R₂As-C₆H₄CO₂H (R = Me, Et, C₆H₁₁, Ph andp-tolyl) with CrO₃ and of their sodium salts withtrans-[CrCl₂(H₂O)₄]Cl·2H₂O in a 31 molar ratio yield three types of oxo/hydroxo bridged complexes:a. CrO(o-R₂AsC₆H₄CO₂)nH₂O (R=Me, n=1.5 or 2.5; R=Et, n=1 or 1.5; R=C₆H₁₁, n=1 or 3; R=p-tolyl, n=4),b. Cr(o-Ph₂AsC₆H₄CO₂)₂(OH)2.5 H₂O andc. Cr(o-R₂AsC₆H₄CO₂)(OH)₂nH₂O (R=Ph, n=1; R=p-tolyl, n=0.5). Their i.r. data favour symmetrical chelation of the carboxylate ion, with the metal ion leaving the arsenic(III) uncoordinated. Suitable dimeric, trimeric and tetrameric structures have been assigned for (i) Typea (R=C₆H₁₁, n=1), (ii) Typea (R=p-tolyl, n=4) and (iii) typea. (R= Et, n=1), Typeb. and Typec. (R=p-tolyl, n=0.5) complexes respectively on the basis of solution spectra and experimental molecular weights and _eff values. Calculated ligand field parameters (10 Dq and B) for all the complexes indicate covalent interaction between the metal ion and the ligands.     

Retention behaviour of51CrO4 2− species on ignited microcrystalline iodates

Summary Influence of pH and that of added lattice and certain non-lattice ions has been studied towards instantaneous sorption of tracer⁵¹CrO₄ ^2– ionic species on iodates of lead, barium and strontium. Carrying is postulated to take place by surface adsorption. In the presence of lattice ions, the mode of deposition is in accordance with the adsorption rules. However, the presence of certain non-lattice cations with similar charge and ionic dimensions produces different types of behaviour. Thus, it has been found that addition of Ba²⁺ or Sr²⁺ ions causes the carrying to fall on Pb(IO₃)₂ surface, Pb²⁺ ions on Ba(IO₃)₂ carrier show the helpful role whereas Sr²⁺ ions supresse the carrying. Both Pb²⁺ and Ba²⁺ ions augment the deposition on the surface of Sr(I0₃)₂. An attempt has been made to explain these findings as a consequence of postulated masking of active adsorption centres on Pb(IO₃)₂ and Ba(IO₃)₂ surfaces under the given experimental conditions.

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Zusammenfassung Der Einfluß des pH sowie der Zugabe von Gitterionen oder manchen gitterfremden Ionen auf die unmittelbare Sorption von⁵¹CrO₄ ^2– an Blei-, Barium- und Strontiumjodat wurde geprüft. Die Trägerwirkung ist als Folge der Oberflächenadsorption anzusehen. In Gegenwart von Gitterionen folgt die Art der Bindung den Regeln der Adsorption. Die Anwesenheit gewisser gitterfremder Ionen mit ähnlicher Ladung und Dimension führt zu verschiedenen Verhaltensweisen. So wurde gefunden, daß die Zugabe von Ba²⁺ oder Sr²⁺ die Trägerwirkung der Oberfläche von Pb(JO₃)₂ vermindert, Pb-Ionen die Trägerwirkung von Ba(JO₃)₂ fördern, während Sr-Ionen sie unterdrücken. Pb²⁺ und Ba²⁺ vermehren die Bindung an der Oberfläche von Sr(JO₃)₂. — Es wurde versucht, diese Feststellungen als Ergebnis der Maskierung aktiver Adsorptionszentren des Pb(JO₃)₂ und Ba(JO₃)₂ unter den gegebenen Versuchsbedingungen zu deuten.

     

Studies on microcapsules

Summary Potentiometric titrations and electrophoretic mobility measurements were made on carboxylated polyphthalamide microcapsules prepared by the interfacial polycondensation method.The values of surface potential and zeta potential of the microcapsules were calculated by using a theoretical potentiometric equation and the simple Smoluchowski equation, respectively.The ionic strength of the medium was found to have no effect on the conformation of the polymer chains of the microcapsules.The negative surface potential obtained from potentiometric titration data rose first with increasing pH of the medium and then tended to level off as the pH approached 7 while the zeta potential as evaluated from electrophoresis data was found to change until the pH attained a value of 10.The cause for this difference in pH change between the surface potential and the zeta potential of the microcapsules was ascribed to the reason that potentiometric titration does not permit the detection of terminal amino groups of the polymer chains constituting the microcapsules, which are far smaller in number than the carboxyl groups, while electrophoresis can detect the presence of the terminal amino groups.

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Zusammenfassung Mit Poly(phthaloyl-l-lysin)-Mikrokapseln wurden potentiometrische Titrationen and elektrophoretische Messungen durchgeführt. Die Größen des Oberflächenpotentials and des Zeta-Potentials der Mikrokapseln wurden unter Verwendung einer theoretischen potentiometrischen Gleichung bzw. der Smoluchowskischen Gleichung berechnet. Es stellte sich heraus, daß die Ionenstärke keinen Einfluß auf die Konformation der Polymerketten der Mikrokapseln ausübt. Das negative Oberflächenpotential, welches aus den potentiometrischen Titrationsdaten erhalten wird, steigt mit dem pH-Wert des Medium bis pH = 7, während das aus den Elektrophoresedaten abgeleitete negative Zeta-Potential mit dem pH-Wert bis pH = 10 zunimmt.Dieser Unterschied zwischen dem Oberflächenpotential und dem Zeta-Potential der Mikrokapseln bei pH-Änderung wird dadurch erklärt, daß bei der potentiometrischen Titration terminale Aminogruppen in den Polymerketten nicht gefunden werden, während die Elektrophorese auf die Anwesenheit terminaler Aminogruppen anspricht.

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With 4 figures     

Complexes of hydrazine and substituted hydrazines with some oxocations

Summary Several new polymeric complexes of general composition MO_n(L)₄X₂ (where M = V, Zr and U; n = 1 or 2; X = Cl, Br, I, NO₃ and NCS and L = N₂H₄, PhNHNH₂ and Me₂NNH₂ have been synthesised and characterized by elemental and d.t. analyses and by magnetic measurements, electronic and i.r. spectra. The vanadyl(IV) complexes exhibit subnormal magnetic moments (1.26–1.36BM) possibly because of exchange interaction between vanadium(IV) ions. The thermal stability of hydrazine complexes fall in the order: Cl>Br>NCS>I. The M-N bond strength, as revealed, by v(M-N), decreases as: Me₂NNH₂>N₂H₄>PhNHNH₂.Presented in symposium on Frontiers of coordination chemistry, Allahabad University, Allahabad, Dec. 6–8, 1979.     

Synthetic studies on stevastelins. 1. Total synthesis of stevastelins B and B3

[Chemical reaction: See text] The synthesis of stevastelin B3 (2) and B (5) are described. In a first approach, epoxy cyclodepsipeptide 8 was considered as a promising candidate for the synthesis of the [15]-membered ring members of the stevastelins; however, the oxirane ring opening, required for the completion of the natural stevastelin synthesis, failed. Thus, we synthesized stevastelin B (5), carrying out the oxirane ring opening earlier in the synthesis and following a synthetic scheme capable of delivering analogues. On the other hand, a translactonization reaction of the [15]-membered ring derivative 59 led to the total synthesis of the natural [13]-membered ring component of the stevastelins family, stevastelin B3 (2).     

Multiple losses of neutral C14H14 in the tandem mass spectrometry of several perbenzyl ether intermediates in the synthesis of green tea constituents

Electrospray and matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry (MS/MS) experiments were used to investigate an unusual fragmentation in collision-induced dissociation (CID) of sodiated and potassiated perbenzyl ether intermediates obtained in the total synthesis of gallate ester constituents of green tea. Prominent fragments correspond to multiple sequential losses of neutral C14H14 that were not observed in the protonated and ammoniated species, that instead present fragment ion series in which members are separated by C7H6. High-resolution MALDI quadrupole time-of-flight (Q-TOF) and electrospray-Fourier transform mass spectrometry (FTMS) were used to confirm elemental compositions of these and related ions.     

Studies on nitrile imines. Synthesis of some new five-membered heterocyclics via N-(2,4-dinitrophenyl)-C-alkyl nitrile imines

Reaction of N-(2,4-dinitrophenyl)-C-alkyl hydrazonyl chlorides with diverse dipolarophiles gave a variety of novel heterocyclics, which are expected to possess biological activities. The ring closure is brought about by a concerted process involving nitrile imine as an intermediate. The structures of the resulting products are supported by nmr and ir spectral data.     

Crystallization kinetics of PHB/PVAc blends using time resolved dielectric spectroscopy

Crystallization kinetics of poly(hydroxy butyrate), PHB, and its blends with poly(vinyl acetate), PVAc, have been thoroughly investigated using broadband dielectric technique over a wide range of frequencies (10⁻²-10⁵ Hz) as functions of crystallization temperature and blend composition. The dielectric strength of the amorphous segments, Δε, which is directly proportional to the volume fraction of the mobile amorphous phase in the blend decreases exponentially with increasing the crystallization time. However, on the other hand, the dielectric strength of the rigid amorphous segments, Δε_α′, which is related to the percentage of crystallinity in the blend increases dramatically with increasing crystallization time. A great variation in the dynamical constraints of relaxation segments with increasing crystallization time has been observed as a result of different environments, which would lead to a variation in the consistency of the cooperative regions. The value of the dielectric constant, ε′, decreases dramatically with increasing crystallization time, after that it reaches an equilibrium value at the end of the crystallization process. This dramatic decrease in the value of ε′ as a result of crystallization at a given crystallization temperature, was taken as an accurate evaluation for the amount of the amorphous phase that has undergone crystallization considering the theoretical approach of Avrami. The Avrami exponent, n, was found to be crystallization temperature, T_c, independent (n ∼ 3) indicating a three-dimensional crystal growth for pure PHB. The crystallization rate constant, k, increases greatly with increasing T_c due to the high crystallization rate. In the blend the value of n was found to be concentration dependent (n ∼ 1.8-3.2). The different values of n indicate that the shapes of the growing crystals are affected by blend concentration. For n ∼ 1.8, the crystals can either grow sporadically as rods or instantaneously as disks, while for n ∼ 3 a three-dimensional crystal growth takes place.     

Excess molar volumes of binary mixtures of γ-butyrolactone and a glycol at 303.15 K

Excess molar volumes at 303.15 K for the binary mixture of ethylene glycol+, diethylene glycol+, triethylene glycol+ and tetraethylene glycol+ γ-butyrolactone were determined from precise density measurements over the whole mole fraction range. The excess molar volumes are positive over the whole mole fraction range for ethylene glycol and diethylene glycol systems. For triethylene glycol and tetraethylene glycol systems, V^E curves are sigmoid with a positive lobe at low mole fraction of glycol and a negative lobe at high mole fraction. The excess molar volumes V^E, results are interpreted qualitatively in terms of several opposing effects.