Phosphorylthioacetamides in the synthesis of annulated quinoxalines

Diethoxyphosphorylthioacetamide in the reaction with 2,3-dichloroquinoxaline acted as a thionating reagent, giving diethoxyphosphorylacetonitrile and 2-chloro-3-[(3-chloro-2-quinoxalinyl)thio]quinoxaline. Reactions of phosphorylthioacetamides with N-methylquinoxalinium iodide in alcohol media in the presence of a base proceeded stereoselectively to afford cis-3-phosphoryl-1,3,3a,4,9,9a-hexahydro-2H-pyrrolo[2,3-b]quinoxaline-2-thiones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1010–1013, May, 2007.     

One-pot synthesis of 5-(substituted-amino)pyrazoles

An efficient and mild one-pot synthesis of substituted 5-alkylamino and/or 5-(arylamino)pyrazoles is described. A suitably decorated β-ketoamide, an aryl or alkyl hydrazine and Lawesson's reagent are suspended in THF/Py and gently heated to yield the requisite 5-aminopyrazoles.     

Analysis of ion binding on humic substances and the determination of intrinsic affinity distributions

Humic substances are characterized by a variable electric potential and by a variety of binding sites leading to chemical heterogeneity. Binding of ions to these substances is influenced by both factors. A methodology based on acid—base titrations at several salt levels is presented that allows for the assessment of an appropriate electrostatic double-layer model and the intrinsic proton affinity distribution. The double-layer model is used for the conversion of pH to pH_S for each data point, where H_S is the proton concentration in the diffuse layer near the binding site. It is shown that with an appropriate double-layer model the proton binding curves at different salt levels converge into one “master curve” when plotted as a function of pH_S. The intrinsic proton affinity distribution can then be derived from the “master curve” using the LOGA method. A rigorous analysis of metal binding to humic substances is complex and in practice is not feasible. Under two different (simplifying) assumptions, namely fully coupled and uncoupled binding, it is shown how intrinsic metal ion affinity distributions can be obtained. Model calculations show that apparent metal ion affinity distributions do not resemble the intrinsic metal ion affinity distribution.     

Isolation of nonprotamine proteins from the nuclei of the gonad cells of the Russian sturgeonAcipenser güldenstadti

Eight nonprotamine proteins have extracted from the nuclei of the cells of the gonads of the Russian sturgeon with 0.35 M sodium chloride solution followed by fractionation of carboxymethyl-Sephadex G-25 and desalting on Bio-Gel P-2, and their amino acid compositions have been determined.     

Two-dimensional separations and behaviour of alkaloids of various polarities on unmodified silica gel in polar and very polar neutral or acidic mobile phases

Summary New separation procedures for alkaloids of similar polarity and structure or of very different polarity and structure, based upon two-dimensional thin-layer chromatography on unmodified silica gel under mild conditions are described. Separation factors and separation mechanisms based on the structure of the bases and mobile phase composition are discussed for some examples of very efficient procedures.Proportions in solvent mixtures are v/v except where otherwise indicated.     

Use of1H and13C NMR spectroscopy to determine the stereochemistry of 1 - methyl- δ4-octalin- 1,2-dicarboxylic acids and their derivatives

Conclusions The combined use of the¹H and¹³C NMR spectra makes it possible to unequivocally assign 1-methyl-⁴-octalin-l,2-dicarboxylic acids and their derivatives to the proper steric series.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1429–1431, June, 1977.     

The determination of alumina in silicates (Rocks and Refractories)

New procedures have been developed for determining the alumina contents of silicate material (rocks and refractories). The material is first taken into solution by a peroxide sinter technique, followed by dissolving the sinter in warm water and the addition of sufficient hydrochloric acid to render the solution acid to litmus. A different technique is used for silicates containing less than 5% alumina. The majority of the silica is first removed by treating with hydrofluoric-sulphuric acids and the residue is fused with potassium bisulphate. Extractions with cupferron are next employed to remove iron, titanium, zirconium etc., and the aluminium is subsequently separated from other sample constituents by precipitating as its insoluble benzoate. After filtration the aluminium benzoate is dissolved in hydrochloric acid and the aluminium concentration determined volumetrically with ethylenediaminetetraacetic acid.     

Antimon(III) und Arsen(III)

Ohne Zusammenfassung     

Interactions of silver halide sols with hydrolyzed hafnium species

Summary Coagulation and reversal of charge effects of freshly prepared and heated solutions of hafnium tetrachloride have been studied as a function of the p_H using aged silver halide sols and solsin statu nascendi. It was shown that the critical coagulation concentration and the critical stabilization concentration (due to charge reversal) increased with increasing p_H. These observations have been related to the hydrolysis of the hafnium ion. At p_H values above 4 essentially the entire amount of hafnium is present in the form of the neutral soluble, species Hf(OH)₄. This accounts for the inability of the hafnium solutions to reverse the charge of the sols at higher p_H values. The adsorption measurements carried out with the aid of the radioactive isotope¹⁸¹Hf showed that the neutral hydrolyzed species are strongly adsorbed on negatively charged silver iodide particles. The adsorbed amounts of hafnium on a AgI sol are considerably larger than in the case of charged hydrolyzed ions (such as hydrolyzed thorium ions) on a similar sol. This is explained by the ability of the neutral hafnium species, Hf(OH)₄. to form a close-packed adsorbed layer. The results confirm previous findings that the enhanced adsorption of hydrolyzed ions is caused by the presence of the hydroxyl group, whereas the ionic charge plays a negligible role in this case.

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Zusammenfassung Die Koagulations- und Umladungserscheinungen von frisch dargestellten und durch Erwärmung gealterten Lösungen von Hafniumchlorid wurden an Silberhalogenid-Solen in der Abhängigkeit vom p_H untersucht. Es wurde festgestellt, daß die kritische Koagulationskonzentration und die kritische Stabilisationskonzentration (die Umladungsgrenze) mit steigendem p_H höher werden. Diese Beobachtungen wurden durch die Hydrolyse des Hafnium-Ions erklärt. Wenn p_H>4 ist, bestcht nahezu die ganze Menge von Hafnium als neutrale, gelöste Hf(OH)₄ Moleküle. Damit wird es erklärt, daß die Silberhalogenid-Teilchen bei höheren p_H-Werten durch Hafniumsalze nicht umgeladen werden können. Die mittels des radioaktiven Isotopen¹⁸¹Hf durchgeführten Messungen zeigten, daß die neutralen Hf(OH)₄ — Moleküle stark an den negativ geladenen Silberjodid-Teilchen adsorbiert sind. Die adsorbierte Menge per Mol von AgI ist beträchtlich größer als die Menge der geladenen, hydrolysierten Ionen (wie z. B. ThOH³⁺), die an dem gleichen Sol bestimmt wurde. Dieser Effekt ist leicht erklärt, da man mit den neutralen adsorbierten Molekülen eine fest gepackte Adsorptionsschicht bilden kann. Diese Resultate bestätigen die früheren Befindungen, daß die höhere Adsorptionsfähigkeit der hydrolysierten Ionen durch die Hydroxylgruppe verursacht wird, während die Ionenladung eine zu vernachlässigende Rolle spielt.

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Supported by the U.S. Army Research Office (Durham), Grant No. DA-ARO (D)-31-124-G 656.

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Part of a PhD Thesis byL. J. Stryker, supported by a NASA Traineeship.     

Thermogravimetric analysis of polycarbonates and polythiocarbonates from diphenols with methyl groups

The thermal behaviour of polycarbonates and polythiocarbonates derived from biphenols with methyl groups in the aromatic rings was studied by dynamic thermogravimetry. The thermal degradation temperatures (TDT) were determined, showing that polythiocarbonates are more stable than the corresponding polycarbonates. The kinetic parameters of the thermal decomposition were determined by using the Arrhenius relationship, and showed two steps for the degradation of the polycarbonates, the first being a zero-order process and the second having first-order kinetics; the steps were associated with two different reaction mechanisms. Polythiocarbonates degraded according to first-order kinetics.