Persulphate initiated polymerisation of methacrylamide—I: Kinetics and molecular weight dependences

A kinetic study of the aqueous persulphate initiated polymerisation of methacrylamide has shown that the rate of polymerisation is represented by the equation $\text{R}{}_{\mathrm{p}}\text{= k [}\text{M}\text{] [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ where the overall rate constant, $\text{k = 1.3 × 10}{}^9\text{exp}\text{(?18,400/}\text{RT}\text{) 1}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{?1}}$. Chain transfer with monomer, where C_M = 5.4 × 10^?3 at 60°, is shown to be the dominant transfer step. Comparison with kinetic studies of the analogous acrylamide polymerisation shed doubt on the ‘cage effect’ interpretation of complex orders with respect to monomer. An alternative explanation is proposed.     

A Photoelectron-spectroscopic investigation of the Homoconjugative Interaction between π- and Walsh-Orbitals in endo- and exo-Cyclopropano-norbornene

Photoelectron spectra of endo- and exo-cyclopropano-norbornene ( = endo- and exo-tricyclo[3.2.1.0^2.4]octa-6-ene) show that a significant homoconjugation exists between the π-orbital of the double bond and the symmetric Walsh-es-orbital of the cyclopropane ring in the exo-isomer, whereas the interaction is negligeable in the endo-derivative.     

Determination de L’oxygene et du fluor au moyen de l’activation par les photons γ et le comptage des neutrons retardes emis par17N

The activation of¹⁸O and¹⁹F by the reactions¹⁸O(γ, p)¹⁷N and¹⁹F(γ, 2p)¹⁷N was determined as a function of the maximum energy of the bremsstrahlung beam. By the use of this method it is possible to measure oxygen or fluorine by counting the delayed neutrons emitted by¹⁷N with a half-life of 4.2 sec.      

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.     

Absorptiometric determination of microgram amounts of uranium with Rhodamine B

Uranium (VI) can be extracted as a complex with rhodamine B into a benzeneetherhexone solvent from a benzoate buffered solution. Optimum conditions for the colour development are defined, leading to a molar absorptivity of 102700 mmol^-1 cm² at 555 nm, the highest yet reported for a uranium complex. The determination of uranium in the range 0.02–3 μg/ml in nitrate samples is described. The relative standard deviation ranges from 20 to 0.6%. The interference of several ions is investigated.     

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.     

Optically active hydrocarbon polymers with aromatic side chains. II. Poly-(S)-p-sec-butylstyrene

The synthesis of optically active p-sec-butylstyrene (I) has been carried out starting with (S)-2-phenylbutane (II) having optical purity 88–91%. The optical purity of I thus obtained was found to be 73–75%. The polymerization of I with stereospecific coordinated anionic catalysts gave amorphous polymers, as in the case of many other p-substituted styrene derivatives. The fractions obtained from these polymers have very similar rotatory power at 589 nm which is practically equal to that of polymer of I obtained by nonstereospecific radical initiator and of low molecular weight structural models. Accordingly the ¹L_b electronic transition of the aromatic chromophore shows a very low rotatory strength in all samples examined. This result is related to the lack in solution of conformations with a predominant single chirality of the main chain of the macromolecules derived from I.     

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.