N 10 N-(2-Carboxyethyl)chitosans: Regioselective synthesis, characterisation and protolytic equilibria [Text] / Yu. A. Skorik, C. A. R. Gomes, M. T.S.D. Vasconcelos, Yu. G. Yatluk // Carbohydrate Research. - 2003. - Vol. 338, № 3. - P271-276 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): CARBOXYETHYLATION POLYSACCHARIDES -- N-(2-CARBOXYETHYL)CHITOSAN -- POLYAMPHOLYTE Аннотация: N-(2-Carboxyethyl)chitosans were obtained by reaction of low molecular weight chitosan with a low degree of acetylation and 3-halopropionic acids under mild alkaline media (pH 8-9, NaHCO3) at 60°C. The chemical structure of the derivatives obtained was determined by 1H and 13C NMR spectroscopies. It was found that alkylation of chitosan by 3-halopropionic acids proceeds exclusively at the amino groups. The products obtained are described in terms of their degrees of carboxyethylation and ratio of mono-, di-substitution and free amine content. The protonation constants of amino and carboxylate groups of a series of N-(2-carboxyethyl)chitosans were determined by pH-titration at ionic strength 0.1 M KNO3 and 25°C. © 2002 Elsevier Science Ltd. All rights reserved. |
C 74 Complexation models of N-(2-carboxyethyl)chitosans with copper(II) ions [Text] / Yu. A. Skorik, C. A. R. Gomes, N. V. Podberezskaya, G. V. Romanenko, L. F. Pinto, Yu. G. Yatluk // Biomacromolecules. - 2005. - Vol. 6, № 1. - P189-195 . - ISSN 1525-7797 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: The copper(II) complex formation equilibria of N-(2-carboxyethyl)chitosans with three different degrees of substitution (DS = 0.42, 0.92, and 1.61) were studied in aqueous solution by pH-potentiometric and UV-spectrophotometric techniques. It was demonstrated that the complexation model of CE-chitosans depends on DS: the [Cu(Glc-NR2)2] complexes are predominant for two lower substituted samples ("bridge model", log ?12 = 10.06 and 11.6, respectively), whereas the increase of DS leads to formation mainly of the [Cu(Glc-NR2)] complexes ("pendant model", log ?11 = 6.41). As a model for copper complexation with a disubstituted residue of CE-chitosan, the complex of N-methyliminodipropionate [CuMidp(H2O)]·(H2O) was synthesized and structurally characterized by XRD. The unit cell consists of two crystallographically nonequivalent Cu atoms having slightly distorted square pyramidal coordination; Midp constitutes the basal plane of the pyramid and acts as a tetradentate NO3 chelate-bridging ligand by the formation of two six-membered chelate rings (average Cu-O 1.99 A, Cu-N 2.04 A) and a bridge via carbonyl O atom (average Cu-O 1.99 A), an apical position is occupied by a water molecule (average Cu-Ow 2.30 A). |
H 43 Heavy metals removal by flocculation/precipitation using N-(2-carboxyethyl)chitosans [Text] / S. YU. Bratskaya, A. V. Pestov, Yu. G. Yatluk, V. A. Avramenko // Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 2009. - Vol. 339, № 1-3. - P140-144 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Here we report on solution properties and flocculation performance of polyampholyte chitosan derivatives - N-carboxyethylated chitosans (CEC) - synthesized "in gel" by treatment of chitosan with acrylic acid. We show that carboxyethylation with the substitution degrees (DS) from 0.7 to 1.6 yields water-soluble derivatives, whose isoelectric points (IEP) range from 6.30 to 3.55. At pH 7.5 interaction of negatively charged CEC derivatives with positively charged colloids of the heavy metal hydroxides (Zn2+, Cu2+, Ni2+), serving as a model of postgalvanic wastewaters, results in lowering of electrokinetic potential of the hydroxide colloids and their precipitation at appropriate flocculant dose. Investigations of CEC flocculation performance depending on pH and DS show that the efficiency of metal removal decreases in the row Cu2+ Zn2+ Ni2+ corresponding to the row of the hydroxocomplex stability for these metals. The higher was pH of the system and DS of CEC derivative, the narrower was the flocculation window and the stronger was negative effect of flocculant overdosing on the efficiency of heavy metal removal. Based on the estimation of floc settling rates and the residual metal concentrations, we have concluded that the optimal DS of CEC derivatives for the precipitation of metal hydroxides is 0.7-1.0 |
A 10 A generalized model of protolytic, complexing and colloidal properties of polyelectrolytes. Case study : N-(2-carboxyethyl)chitosans [] : доклад, тезисы доклада / S. YU. Bratskaya, A. Golikov, A. V. Pestov, A. Voit, Yu. G. Yatluk, V. A. Avramenko // EUCHIS 2009 - 9th International Conference of the European Chitin Society , Venice, Italy, 23-26 May 2009 : conference book. - Venice, Italy, 2009. - 21 (P1-5) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
К 44 Кислотно-основные и коллоидные свойства N-(2-карбоксиэтил)хитозанов [] = Acid-base and colloid properties of N-(2-carboxyetil)chitosans : доклад, тезисы доклада / С. Ю. Братская, А. В. Пестов, А. П. Голиков, Ю. Г. Ятлук, В. А. Авраменко // Современные перспективы в исследовании хитина и хитозана : материалы IX Международной конф., Ставрополь, 13-17 окт. 2008 г. : докл. - Ставрополь, 2008. - С. 49-52. - Библиогр.: с. 52 (7 назв.) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
T 45 Thiocarbamoyl chitosan: Synthesis, characterization and sorption of Au(III), Pt(IV), and Pd(II) [Text] / S. YU. Bratskaya, A. Yu. Ustinov, Yu. A. Azarova, A. V. Pestov // Carbohydrate Polymers. - 2011. - Vol. 85, № 4. - P854-861 : ил. - Bibliogr. : p. 860-861 (39 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Here we suggest a new method of chitosan sulfur derivatives (thiocarbamoylchitosans, TC-chitosans) synthesis via reaction in eutectic two-component system ammonium rodanide–thiourea that allows significant increase of substitution degrees at the reduced time and reagent consumption as compared to conventional synthetic procedures. The sorption properties of TC-chitosans with substitution degrees (DS) from 0.4 to 0.9 toward Au(III), Pt(IV), Pd(II) ions were studied in chloride solutions, including systems with 10 to 1000-fold excess of Fe(III), Cu(II), and Zn(II) over the precious metal ions content. The sorption capacities of TC-chitosans increase with DS and change in the row: Au(III) Pd(II) Pt(IV) ? Cu(II) Fe(III) Zn(II). The maximum sorption capacities of TC-chitosan with DS 0.9 for Pt(IV), Pd(II), and Au(III) were 1.24 mmol/g, 3.43 mmol/g, and 3.81 mmol/g, respectively. Characterization of precious metals oxidation states by the XPS method after the sorption on TC-chitosan revealed that the platinum and gold recovery occurred with reduction of Au(III) to Au(I)/Au(0) and Pt(IV) to Pt(II)???? \\\\Expert2\\nbo\\Carbohydrate Polymers\\2011, v. 85, p.854.pdf |
P 91 Preparation of a sorbent for metal ions based on N-(5-methylimidazol-4- ylmethyl) chitosan with medium degree of substitution [Electronic resource] / A. V. Pestov, M. A. Ezhikova, M. I. Kodess, Yu. A. Azarova, S. YU. Bratskaya // Russian Journal of Applied Chemistry. - 2014. - Vol.87, №1. - С. 82-87. - Bibliogr. : p. 87 (27 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): HETEROCYCLE-CONTAINING CHELATING -- CHITOSANS -- AMINO POLYMER Аннотация: A procedure was developed for preparing a heterocycle-containing chelating amino polymer, N-(5-methylimidazol-4-ylmethyl) chitosan, by polymer-analogous transformations of chitosan in reaction with 4-chloromethyl-5-methylimidazole. The procedure allows synthesis of the polymer with the degree of substitution of up to 0.8, with simultaneous formation of the cross-linked structure. The structure of the polymers prepared was proved by IR and 13C NMR spectroscopy. The ability of N-(5-methylimidazol-4-ylmethyl) chitosan with the degree of substitution of 0.54 to sorb Cu2+ and Ni2+ ions was evaluated. According to the sorption isotherms, the sorption capacity of this derivative exceeds that of the unmodifi ed polymer by a factor of 5. \\\\expert2\\nbo\\Russian Journal of Applied Chemistry\\2014, v. 87, N 1, p.82-87.pdf |