Study of the microstructure of tetrahydrofuran-3,3 dimethyloxetane copolymers by 13C-NMR spectroscopy.

The microstructure of tetrahydrofuran (A)-3,3 dimethyloxetane (B) copolymers was studied by ¹³C-{¹H}-NMR spectroscopy. Only the methyl carbons corresponding to the 3,3 dimethyloxetane unit appear as a singlet, whereas the other carbons present a more complicated spectral pattern than it would be expected if ? effects were negligible. The assignment of the resonance signals allowed the determination of the values of the probabilities of the different triads, which were in good agreement with those obtained from the reactivity ratios.     

Application of ESCA to polymer chemistry. VIII. Surface structures of AB block copolymers of polydimethylsiloxane and polystyrene

The surface morphology of a number of films of AB block copolymers of polydimethylsiloxane and polystyrene was examined by ESCA and contact angle measurements. In all cases the immediate surface is shown to consist of an essentially pure polydimethylsiloxane component. By comparing the intensities of elastic peaks corresponding to photoionizations from core levels without energy loss for polydimethylsiloxane and polystyrene with those for the block copolymers and by consideration of shake-up phenomena specific to the polystyrene component, an estimate of the thickness of the polydimethylsiloxane outer layer of the latter may be obtained. This is shown to vary between ～13 and 40 Å, depending on the method of formation of copolymer film.     

Zur Kenntnis der thermischen Zersetzung von Ammoniumhexafluoroscandat,-titanat,-vanadat und-chromat

Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described.     

Hétérocyclisations intramoléculaires par réaction d'oxymercuration. I — synthèse et configurations des hétérocycles

We have accomplished the intramolecular oxymercuration of γ-δ ethylenic alcohols, with different mercuric salts under different conditions. By “in situ” reduction, or by direct reduction of isolated mercuric compounds, we obtain, in some cases, diastereoisomers with different relative yields.     

Spectrophotometric determination of the protolytic dissociation constants of the new chromogenic reagent "palladiazo"-I Investigations with sodium hydroxide, perchloric acid and different aqueous buffer solutions

The "palladiazo" reagent has been subjected to a detailed spectrophotometric investigation in concentrated perchloric acid, different aqueous buffers and concentrated sodium hydroxide solutions. K(1)-K(10) and (1)-(10) values corresponding to the instability constants of the protolytic equilibria involved and to the molar absorptivities at 540 and 630 run of the different proton complex species of the system have been calculated by a number of analytical and graphical spectrophotometric methods. Special attention has been paid to the study of the complicated phenomena implied by the interaction of the reagent with perchloric acid, which has been shown to give rise to alteration of the initial isomeric composition of the reagent and to the formation of addition and/or oxidation products derived from side-reactions undergone by the reagent with the medium. All the instability constants and molar absorptivities, which have been determined by several methods, are tabulated for comparison.     

Critical evaluation of spiking of low-grade ore samples in activation analysis for gold and uranium

In applying non-destructive neutron-activation analysis for gold and uranium in spiked low-grade ore samples, the following extrapolated unspiked concentrations were measured: 0.27₈ ± 0.01₅ ppm gold (chemical assay: 0.20₂ ± 0.02₀ ppm gold); 25.1 ± 1.1 ppm uranium (chemical assay value: 19.5 ±2.0 ppm uranium). Different approaches to the fitting of results, and the influence of spiking non-uniformity, are discussed.     

Elemento-Organic Amines and Imines

Amines with mixed substituents containing two or three El? N bonds

1 El = a higher IVa, Va, or VIa element; by IVa, Va, and VIa elements are meant elements of the IV, V, and VI main groups of the periodic system

. are relatively stable if one or two of these bonds are (CH₃)₃ Si? N bonds. IR and ¹H? NMR studies indicate that the (p → d)π bond components of the element-nitrogen bonds steadily decrease from silicon, phosphorus, and sulfur toward their higher homologs. Because of the differences in the polarities of the element-nitrogen bonds, these substances can be used for selective insertion and cleavage reactions. The reaction of metalated N-silylaminoarsines with methyl chloride as well as the reaction of metalated N-trimethyl(IVa)-element-substituted amino-tert-butylphosphines with halogenotrimethyl(IVa) element compounds open new, simple routes for the conversion of elemento-organic amine systems into imine systems. The problem of reversible and irreversible (CH₃)₃ El ligand migration (1,3 shift) is discussed for trimethyl(IVa)element-substitued benzamidines, diaminophosphines, aminoiminophosphoranes, sulfinamides, and aminosulfimines.     

Studies on Ziegler-Natta catalysts. Part II. Reactions between α- or β-TiCl3 and AlMe3, AlMe2Cl,or AlEt3 at various temperatures

The following reactions, carried out in the absence of solvents, has been studied: α-TiCl₃ + Al(CH₃)₃ at 20°C., β-TiCl₃ + Al(CH₃)₃ at 65°C., α-TiCl₃ + Al(CH₃)₂Cl at 20 and 65°C., and α-TiCl₃ + Al(C₂H₅)₃ between 30 and 65°C. It appears that a general reaction mechanism, such as discussed in the preceding paper of this series, applies to all these reactions between TiCl₃ and aluminum alkyls. The differences in overall stoichiometry between some of these systems may be linked to differences in stability of the intermediate Ti? C bonds. In the case of α-TiCl₃ + Al(CH₃)₂Cl, alkylation is probably accompanied by fixation of the AlCH₃Cl₂ on the nonvolatile product.     

Zur Kenntnis der Verbindung H3P–BJ3

Phosphine or phosphonium iodide react with boron triiodide in CS₂ or benzene to form the adduct H₃P–BI₃. The water-sensitive white solid is thermally stable up to ～150°C. Its IR and NMR spectrum are recorded.     

Kettenverzweigung bei der Polymerisation von Vinylchloracetat und Vinylacetat

Zusammenfassung Bei niedrigen Umsätzen und einer Polymerisationstemperatur von 50°C erhaltene Polyvinylacetate sind unverzweigt; das gleiche gilt für Polyvinylchoracetate. Bei diesen wurde die bei höheren Umsätzen auftretende Verzweigung durch Verseifung und Acetylierung der Polymeren sowie durch Messung von []-, und Werten an den Polymeren bestimmt. Eine Selbstverzweigung der wachsenden Kette konnte nicht gefunden werden. *** DIRECT SUPPORT *** A3615144 00012

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Chain branching in vinyl chloroacetate and vinyl acetate polymerization

Polymerization of vinyl acetate and vinyl chloroacetate to low conversions at 50°C gave unbranced polymers. The branching of polyvinyl chloroacetates at higher conversions was determined by hydrolysis and acetylation of the polymers and by measuring [], and . No self-branching of the growing chains could be found.