Chemoselective acylation of monosubstituted thiacalix[4]arene with di-<Emphasis Type="Italic">tert</Emphasis>-butyl dicarbonate

Mono-, di-, and tetrasubstituted derivatives of p-tert-butylthiacalix[4]arene containing tert-butylcarbamate, tert-butylcarbonate, and tert-butyl fragments have been prepared for the first time. Depending on the reaction conditions (reagents ratio, temperature, and the presence of a base), the interaction of the monoamine derivative of p-tert-butylthiacalix[4]arene with di-tert-butyl dicarbonate can lead to the formation of mono-, di-, and tetrasubstituted products.     

Modification of silica nanoparticles with stereisomers of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene containing four 2-oxo-2-{[3-(triethoxysilyl)prop-1-yl]amino}ethoxy substituents at the lower rim

Three stereoisomers (cone, partial cone, and 1,3-alternate) of p-tert-butylthiacalix[4]arene bearing four anchor propyltriethoxysilane substituents at the lower rim were synthesized for the first time. Surface modification of silica nanoparticles (d = 12 nm) with the synthesized macrocycles gave novel hybride thiacalix [4]arene?SiO₂ particles. The obtained nanostructured adsorbents were found to efficiently extract nitroaromatic compounds from aqueous solutions. The partial cone and 1,3-alternate thiacalix[4]arene–SiO₂ hybrid particles showed affinity to nitrophenols.     

On the derived algebra of a centraliser

Let g be a classical Lie algebra, e∈g a nilpotent element and ge⊂g the centraliser of e. We prove that ge=[ge,ge] if and only if e is rigid. It is also shown that if e∈[ge,ge], then the nilpotent radical of ge coincides with [ge(1),ge], where ge(1)⊂ge is an eigenspace of a characteristic of e corresponding to the eigenvalue 1.     

Determination of platinum by atomic absorption spectrometry with chromatographic preconcentration from aqueous solutions

The conditions for determining platinum by electrothermal atomic absorption spectrometry after its extraction-chromatographic preconcentration and separation from iron(III) and copper(II) were selected. A procedure was developed that allows 0.01–0.1 mg/L platinum to be determined with a relative standard deviation of 5–7 % in the presence of 1000-fold amounts of Fe(III) and Cu(II).Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 41–44.Original Russian Text Copyright © 2005 by Moskvin, Yakimova, Alekseeva.     

Superacids as catalysts of the oxidation of inorganic substrates

The oxidation of sulfur dioxide, nitrogen dioxide, carbon monoxide, etc., in anhydrous trifluoroacetic acid (TFA) at room temperature was observed. The oxidative ability of anhydrous TFA in reactions with inorganic substances was shown to be related to molecular oxygen dissolved in it. The dissolved molecular oxygen endowed TFA with the properties of a superacid with pK _a ? ?12. Mechanisms of active oxygen reactions with inorganic substrates were suggested.     

Determination of alkylamines in aqueous media by capillary electrophoresis

A procedure is developed for the determination of organic amines in potable water and wastewater by capillary electrophoresis. A mixed solution of benzimidazole and tartaric acid is selected as a leading electrolyte for indirect photometric detection. The sample was injected hydrodynamically. The procedure was tested on samples of potable water and wastewater. The accuracy of the results was evaluated by the standard addition method. The analytical range is 0.25–5 mg/L. The analysis time is 4–5 min.     

Fast isotopic separation of 10B and 11B boric acid by capillary zone electrophoresis

Fast isotopic separation of ¹⁰B and ¹¹B boric acid by CZE was demonstrated. The BGE contained 25 mM phenylalanine and 5 mM putrescine (рН 8.95). The running conditions were +25 kV at 20°C with indirect photometric detection at 210 nm. Baseline separation was achieved in less than 9 min. RSD of migration times and corrected peak areas were less than 0.5 and 3%, respectively (n = 5). Linearity was demonstrated in the range 0.2–2 mM for ¹¹B and 0.2–0.5 mM for ¹⁰B.     

Guest exchange in dimeric capsules of a tetraurea calix[4]arene in the solid state

A solid powder of hydrogen bonded dimers of a tetraurea calix[4]arene is able to exchange the encapsulated guest in contact with the vapor of a second guest. The molecules of a guest-free powder obtained from a polar solvent cannot rearrange in the solid phase to form new guest-filled capsules under these conditions.