Arylsulfimide Polymers. VI. Polysaccharins of the AA-BB Type

m-Bisaccharin and related derivatives have been condensed with p-phenyl-enediamine or benzidine. The polymerizations were carried out in melts and in solutions in dimethylacetamide and in polyphosphoric acid. In contrast to the results obtained in the A-B system, hemipolymers isolated from melts incorporating m-bisaccharin underwent considerable ring closure. Postheated polymers of the AA-BB type exhibited thermal stabilities comparable to those found in the A-B series.     

Studies in heterocyclic polymers. Part VI. A weight-loss study of the formation of a polybenzoxazole

The cyclisation of an aromatic poly(o-hydroxyamide) to form polybenzoxazole has been studied by combining isothermal weight-loss and thermogravimetric analyses. The thermogravimetric data were analysed by the method of Gyulai and Greenhow [4] to derive values for the apparent activation energy of the cyclisation process which was found to double at about 50% conversion (74–155 kJ mole^?1. A similar result was observed when the process was studied in the presence of low concentrations of p-toluene sulphonic acid, which appears to have a moderate catalytic effect upon the cyclisation process. The apparent order of reaction of the process has been found to be close to 2, contrary to previous studies which have assumed it to be unimolecular.     

Finite-field many-body perturbation theory. VI. Multipole polarizabilities of beryllium. A comparative study

A high-resolution ESCA N1s spectrum from free p-aminobenzonitrile molecules is presented. The spectrum is very different from the corresponding spectrum from a solid sample. It shows one uncommonly intense shape-up line from the N1s ionization in the nitrile group, while ionization in the NH₂ group does not give rise to any such anomalous shake-up features. The spectrum is theoretically analyzed by means of a large-scale ab initio calculation by the CAS SCF method, in which a full π-orbital active space was employed for the ground and N1s ionic states. The calculations strongly underline the role of multiple excitations in the charge transfer following N1s(CN) ionization, as well as the importance of separate self-consistent treatment of all states involved. In particular, it is shown that an unsuitable choice of orbitals can lead to an apparent “shake-down”.     

Synthesis and study of boron trifluoride-based catalytic complex participating in hexafluoropropylene sulfotrioxation

Catalytic complexes of boron trifluoride and sulfuric anhydride were experimentally detected and studied by the ¹⁹F NMR method.

     

色谱法研究杂多酸VI. 12-钨硼酸根离子溶液中降解反应的研究

本文将胶束液相色谱用于α-BW~12O~40^5-溶液中降解反应的研究。首次发现α-BW~12O~40^5-降解存在两个过程。第一步为α-BW~12O~40^5-向其异构体转化的快速平衡反应, 第二步为该异构体的缓慢降解。实验测定了杂多酸离子浓度、pH值、无机盐逍度、温度对降解反应的影响, 得到第一步反应的平衡表达式和第二步反应的速率方程式, 推断了α-BW~12O~40^5-降解反应的机理。     

Using the liquid nature of the stationary phase. VI. Theoretical study of multi-dual mode countercurrent chromatography

Countercurrent chromatography (CCC) is a separation technique using a biphasic liquid system and centrifugal forces to maintain a support-free liquid stationary phase. Either one of the two phases can be the liquid stationary phase. It is even possible to switch the phase role during the separation. The dual-mode method is revisited recalling its theoretical background. The multi-dual mode (MDM) CCC method was introduced to enhance the resolution power of a CCC column. The theoretical study of the MDM method is validated by modeling the separation of two solutes. The basic hypothesis is that the forward step (partial classical elution) is followed by a backward step that returns the less retained solute to the column head. The equations show that the most important parameter to maximize resolution is not the number of MDM steps but the total volume of liquid phases used to elute the solutes. The model is validated calculating correctly the peak position of previously published MDM experiments.     

Four-center type photopolymerization in the crystalline state. VI. Kinetic and structural study of the polymerization of p-phenylenediacrylic acid diethyl ester

The effect of temperature on the four-center type photopolymerization has been investigated for p-phenylenediacrylic acid diethyl ester over a wide temperature range including crystal transition point (56°C) and melting point (96°C) of monomer. With the elevation of temperature between ?50 and 15°C, the polymerization rate in the initial stage increased and the degree of polymerization decreased monotonously, while the rate in the later stage decreased above ?25°C. With irradiation at above 25°C, the monomer crystals became sticky, and the polymerization was suppressed at the stage of oligomerization with low conversion. This tendency was enhanced above the crystal transition point, giving mainly dimer in low yield. Above the melting point, only radical polymerization occurred with the aid of oxygen. The steric configuration of the products in the crystalline state was 1,3-trans with respect to the cyclobutane ring. Peaks in NMR spectra of all products were assigned to the protons involved in four compounds up to tetramer. Various results obtained have been interpreted in terms of the change, as a function of temperature, from a topochemical polymerization which proceeds under a control of the monomer lattice to a photoinitiated vinyl-type polymerization in the disordered state. It is concluded that a rigid crystal lattice is indispensable for the four-center type photopolymerization to proceed smoothly.     

Die Phosphorbestimmung in organischen Substanzen. VI

Zusammenfassung Die Fehler bei der Verbrennung phosphorhaltiger Substanzen im Sauerstoffkolben sind zu beseitigen durch Mitkochen des Platinnetzes bei der Hydrolyse und Hydrolysieren in basischer und saurer Lösung. Es konnte nachher keine Bildung von Platin-Phosphor-Verbindungen oder Verluste durch Auftreten von anderen Phosphaten als Orthophosphat nachgewiesen werden. Die Verbrennung an einem 25-mesh-Netz ist erforderlich.

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The determination of phosphorus in organic substances. VI

Summary During the burning of phosphorus containing organic compounds in an oxygen flask often losses of phosphorus occur. These losses are avoided by simply putting the platinum gauze in the absorption solution and hydrolysing in basic and acidic solution. There remained no platinum-phosphorus compounds after this procedure. Losses due to the formation of other phosphates as orthophosphate did not occur. Burning in a 25-mesh platinum gauze is recommended.

     

Electron-donor-acceptor complexing reagents in the analysis of pesticides. VI

Summary Pesticides may be detected following thin-layer chromatography by spraying the chromatogram with a reagent which forms a-complex with the pesticide. The effect of various pesticide structures and substituents in choosing a suitable-complexing reagent is discussed, as well as the effect of these factors in influencing the colour of the complex formed. Quantitative analyses may be performedin situ on the thin-layer chromatogram and positive identification of the-complexed compounds may be made by mass spectrometry. The procedure should be applicable for formulation analysis or studies of pesticide decomposition.

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Zusammenfassung Zum Nachweis von Pestiziden besprüht man deren Dünnschichtchromatogramme (DC) mit einem zur Bildung eines-Komplexes geeigneten Reagens. Die Bedeutung verschiedener Pestizidstrukturen und -Substituenten bei der Wahl eines solchen Reagens wurde erörtert; ebenso der Einfluß der genannten Faktoren auf die Farbe des Komplexes. Quantitative Bestimmungen lassen sich unmittelbar auf dem DC, Nachweise der einzelnen komplexierten Verbindungen mit Hilfe der Massenspektrometrie durchführen. Das Verfahren eignet sich zur Strukturanalyse sowie zur Untersuchung von Pestizidabbauproblemen.

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Issued as NRCC No. 13120.     

Studies on lanthanoid sulfites: Part VI. Thermogravimetric study of scandium sulfite pentahydrate

Scandium sulfite was found to crystallize as a pentahydrate both at 25 and 90 °C when precipitated by the action of sulfur dioxide on aqueous suspensions of Sc(OH)₃. Thermogravimetric analysis showed that the anhydrous sulfite is formed by 200 °C but it starts to decompose immediately after its formation. The decomposition leads to an intermediate phase which is stable up to 700 °C in inert (nitrogen) and air atmospheres but decomposes earlier in reductive (hydrogen) environment. The weight remaining, which corresponds to the intermediate level, varies between 58 and 43 %, depending on experimental conditions and thus cannot be assigned to a single compound such as Sc₂O₂SO₄ or Sc₂O₂SO₃. The intermediate phase is amorphous to X-rays but IR spectra indicate the presence of both sulfite and sulfate ions pointing to a mixture. In all atmospheres studied the final decomposition step is the formation of scandium sesquioxide.     

31P-NMR study of the organophosphorous complexes of uranium(VI)

The intermolecular ligand exchange in uranyl nitrate complexes with TBP and TOPO is studied by³¹P-NMR. The constant rates at 25°C in CCl₄ are: (8.47±1.86)·10³ s^?1 for U-TBP and (1.3±0.04)·10⁴M^?1·s^?1 for U-TOPO system. The very similar activation parameters values of the ligand exchange suggest the same mechanism for both systems, namely an one-step interchange mechanism. The differences between the systems regarding the rate equations and the extraction properties are discussed.     

Emulsion polymerization. VI. Concentration of monomers in latex particles

Nonpolymerizing latex particles surrounded by an aqueous phase saturated with monomer absorb only a finite amount of monomer, even if the monomer is a good solvent for the polymer, because the surface energy of each particle increases on swelling. At equilibrium the change in surface energy and the free energy of mixing exactly balance. Equations based on this thermodynamic principle predict with good accuracy the saturation swelling of crosslinked and uncrosslinked latex particles and the partitioning of monomer between the aqueous phase and latex particles at partial saturation. The available experimental data on swelling of latex polymers with monomers are reviewed. Earlier papers assumed that during emulsion polymerization the monomer concentration in the latex particles is independent of conversion as long as monomer droplets are present. This assumption is shown to be a justifiable approximation. The thermodynamics of the swelling of latex particles with a blend of two monomers is presented. The calculations indicate that copolymerization in emulsion should define reactivity ratios differing from those of homogeneous copolymerization by not more than 40% if the solubility of the comonomers in water is low. The reactivity ratio scheme is strictly applicable to emulsion copolymerization if the solvent properties of the two comonomers are identical.