Study of the direct detection of crosslinks in hydrocarbons by 13C-NMR. I. Preparation and characterization of model compound 1,1,2,2-tetra(tridecyl) ethane

The present series of papers is the commencement of a study aimed at the direct detection and quantification of crosslinking in hydrocarbons with the ultimate objective of a precise study of radiation-induced crosslinking in polyethylene. The subject of the present paper is the synthesis of a model compound containing a crosslink in a well-defined position sufficiently remote from the chain ends to be representative of an average crosslink in polyethylene. Such a compound in the form of 1,1,2,2-tetra(tridecyl) ethane has been synthetized and isolated in pure form in the course of the present work. Melting points and x-ray spacings of the new compound have been determined, and a comparison with the corresponding linear paraffins has been made. Effects are noted relating to the influence of molecular shape on the GPC elution volume, in which context an observation on a cyclic paraffin is also quoted.     

On the extraction of mineral acids and uranium from alcoholic and acetonic solutions with tri-N-butyl phosphate

The extraction of hydrochloric, nitric, and sulphuric acids with TBP was studied as a function of methanol, ethanol, isopropanol, and acetone concentration in the aqueous phase. Extraction increases in the order: methanol相似文献   

Acylsilanes from the pyrolysis of silyl esters of α-ketoacids

The pyrolyses of silyl esters of pyruvic acid and phenylglyoxylic acid gave rise to acylsilanes in high yield. An intramolecular rearrangement involving an intermediate siloxycarbene is proposed to account for the reaction.     

Aroma analysis in food chemistry by GC/MS techniques: Determination of natural and artificial coconut flavour

Summary It is shown that the grazing-incidence grating monochromator with the crossed mirror-grating X-ray optics and a windowless electron multiplier can be used effectively in the electron probe analyser for microanalysis of beryllium.

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Elektronenstrahlmikroanalytische Bestimmung von Beryllium mittels eines Gitterspektrometers

Zusammenfassung Es wird gezeigt, daß ein Gitterspektrometer mit gekreuzter Spiegelgitter-Röntgenoptik in Verbindung mit einem offenen Elektronenvervielfacher vorteilhaft für die Elektronenstrahlmikroanalyse von Beryllium verwendet werden kann.

     

Heteronuclear solid-state correlation spectroscopy

Two-dimensional NMR methods are proposed for correlating the spectra of abundant and dilute spins in solids. The techniques simplify assignment and permit determination of shielding tensors even when extensive overlaps occur. Spin diffusion among abundant spins can be observed indirectly.     

Electron paramagnetic resonance study of partially oriented clay platelets intercalated with copper(II) 1,4,8,11-tetraazacyclotetradecane

Electron paramagnetic resonance (EPR) spectra of powder and oriented films of montmorillonite, hectorite, and saponite intercalated with [Cu(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) exhibit three components: an orientation-dependent component without hyperfine features, an orientation-dependent component with hyperfine features, and an orientation-independent component without hyperfine feature. EPR spectra of [Cu(cyclam)](2+)-saponite, which exhibit only two components and the best resolved hyperfine features, were simulated. The spectra indicate that a large portion of the saponite platelets are inclined to the glass surface, although they tend to align with their basal planes parallel to the glass surface. The orientation-dependent spectra could be simulated by introducing a Gaussian distribution with a standard deviation of 20 degrees for the inclination angle. The standard deviation may be used as a disorder parameter for the microcrystals assembled on glass plates. Spectral simulation also shows that the CuN(4) plane of [Cu(cyclam)](2+) is parallel to the clay layers. EPR spectra of some other partially oriented systems are also discussed.     

Phosphorylation of lignins I. Phosphorylation of piperidinomethylated dioxane lignin from cottonseed husks

The phosphorylation of piperidinomethylated dioxane lignin has been studied. It has been shown that the reaction takes place with the formation of quaternary ammonium phosphates, while the transesterification of dimethyl phosphite with an aliphatic hydroxy group of the lignin is also possible.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 275–277, March–April, 1993.     

Kinetic Model of the Decomposition of Sodium Hydroxymethanesulfinate in Aqueous Solution

A kinetic model of the decomposition of sodium hydroxymethanesulfinate (rongalite) in aqueous solution at an initial value of pH 7.9 was considered. This multistep reaction was found to include oxidation decomposition in a solution surface layer and bulk reactions both with and without the participation of oxygen. To evaluate the parameters of this model, it was modified over three time intervals. The adequacy of this model to experimental data supported the hypothesis on the catalytic effect of active sulfur in the decomposition of rongalite.