Supramolecular catalytic systems based on 1, 4-diazabicyclo[2.2.2]octane,its alkylated quaternary derivatives,and lanthanum nitrate

Spectrophotometry was used to study the catalytic effects of the systems composed of N-monoand N, N-dialkylated 1, 4-diazabicyclo[2.2.2]octanes and lanthanum nitrate on the hydrolysis rate of O-alkyl O-4-nitrophenyl chloromethylphosphonates (Alk = Et, Buⁿ, and n-hexyl). The mechanism of action and efficiency of the catalytic system depend on the structure of the heterocycle, its propensity to aggregation and complexation with the lanthanum cation, and the relative content of the components in solution. The maximum catalytic effect (a ～115-fold increase in the hydrolysis rate constant) was achieved in micellar solutions of the cationic monoalkylated derivative of 1, 4-diazabicyclo[2.2.2]octane and lanthanum nitrate.

     

Polysaccharides of algae 67. Carrageenan from Pacific red alga Turnerella mertensiana (Gigartinales,Rhodophyta)

A sulfated galactan composed of nearly equimolar amounts of d-galactose, 3,6-anhydro-d-galactose, and sulfate was isolated from the red alga Turnerella mertensiana collected in the Sea of Japan. The structures of native polysaccharide and its alkaline modification products were studied by NMR spectroscopy. The polysaccharide molecules were shown to contain a linear carbohydrate chain consisting of alternating 3-linked β-d-galactopyranose 4-sulfate and 4-linked 3,6-anhydro-α-d-galactopyranose residues (known as к-carrageenan), which is typical of carrageenans, but the regularity of polymer structure is masked by the presence of some 3,6-anhydro-α-d-galactose 2-sulfate (ι-carrageenan units) and α-D-galactose 6-sulfate (µ-carrageenan units) instead of 3,6-anhydro-α-d-galactose. Upon addition of potassium chloride (up to 4%) to a solution of the native polysaccharide, about half of the substance transforms into gel. The gel-forming fraction is к-ι-µ-hybrid carrageenan with the ～65 : 15 : 20 ratio of к-, ι-, and µ-units. The non-gelling fraction contains the к-, ι-, and µ-units at the ratio of ～46 : 12 : 42. The gel-forming carrageenan product free of µ-units can be otained in ～30% yield (based on the dry biomass) by alkaline treatment of the alga prior to extraction of the polysaccharide.

     

The characteristics of the hydrotropic Miscanthus pulp

Russian Chemical Bulletin - The characteristics of the Miscanthus pulp obtained by hydrotropic processing under different conditions were studied. The pulping conditions were optimized to achieve...     

Development of new methods for the synthesis of 2,3-bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate and its intermediates

Known methods for the synthesis of 2,3-bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate and its intermediates were investigated. New procedures were developed for the preparation of these compounds. 2,3-Bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate was studied by X-ray diffraction.

     

Ultrasound synthesis of diaryl ethers

Russian Chemical Bulletin - 2,2-Bis[4-(4-nitroaryl)phenyl]hexafluoropropanes appropriate for the synthesis of monomers were prepared by the reaction of 2,2-bis[4-hydroxyphenyl)hexafluoropropane...     

Kinetic features of ammonium persulfate decomposition in aqueous medium

Russian Chemical Bulletin - Decomposition of ammonium persulfate in an aqueous medium (353–368 K) is limited by decomposition of persulfate ions with a rate constant logk 2 =...     

Synthesis of new types of aminomethylenediphosphorus-containing acids and their derivatives

Convenient methods for synthesis of various aminomethylenediphosphorus-containing acids and their derivatives starting from available trimethylsilyl esters of hypophosphorous and phosphorous acids, ethoxymethyleneimine hydrochlorides, and N-substituted formamides have been proposed. Selected properties of the obtained compounds have been examined.

     

Coordination properties of trimeric porphyrin in acetic acid

Trimeric porphyrin H₆TP as well as its binuclear Cu₂H₂TP and trinuclear Cu₃TP copper complexes have been prepared. Kinetic features of H₆TP and Cu₂H₂TP complexes formation with copper(II) acetate in acetic acid as well as dissociation kinetics of Cu₂H₂TP and Cu₃TP in acetic acid medium in the presence of sulfuric acid have been studied.     

Synthesis and photochemical properties of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole derivatives

Method of synthesis has been developed for a series of 3,6-di-tert-butyl-9H-carbazole derivatives and their photochemical properties have been investigated. The dependence of the Steglich esterification reaction on the nature of the catalyst was studied. The synthesized compounds show fluorescent emission in the range 400–600 nm with a high quantum yield.