Condensation of Ketones in the Presence of Titanium Alkoxides

itanium alkoxides promote successful condensation of aromatic and aliphatic ketones provided that the liberated alcohol is selectively removed from the reaction mixture.     

Protolytic Equilibria of Some N,N-Bis(2-carboxyethyl)aminoazobenzenesulfonic Acids in Aqueous Solution

4-[4-Bis(2-carboxyethyl)aminophenylazo]benzenesulfonic acid and 4-[2-bis(2-carboxyethyl)amino-4,5-dimethylphenylazo]benzenesulfonic acid were synthesized for the first time by azo coupling of diazosulfanilic acid with N,N-bis(2-carboxyethyl)aniline and N,N-bis(2-carboxyethyl)-3,4-xylidine, respectively. The acid ionization constants of the products were determined, their electron absorption spectra were measured, and schemes of acid-base equilibria in aqueous solution were proposed.     

New hybrid chelating sorbents with grafted 3-aminopropionate groups based on mixed silicon,aluminum, titanium,or zirconium oxides

A series of new hybrid organo-inorganic sorbents with the 3-aminopropionate chelating group was synthesized. The synthesis includes the copolycondensation (sol—gel method) of tetraethoxysilane, 3-aminopropyltriethoxysilane, and several modifiers (MeSi(OEt)₃, EtSi(OEt)₃, Ti(OEt)₄, AlONO₃, ZrOCl₂) followed by carboxyethylation with acrylic acid. The obtained chelating sorbents were characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy, and thermogravimetry. The N-carboxylated sorbents have a higher sorption capacity with respect to metal ions (0.5–0.9 mmol g⁻¹, pH 6.3, NH₄OAc, 20 °C) than the starting sorbents with the primary amino group (0.05–0.2 mmol g⁻¹) and manifest high selectivity for copper(II) ion extraction. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1783–1788, August, 2005.     

Solid-state structure of copper complexes of <Emphasis Type="Italic">N</Emphasis>-(2-carboxyethyl)chitosan

The sorptivity for ions of the Irving-Williams series (Zn²⁺, Cu²⁺, Co²⁺, Ni²⁺) was estimated for the chelate sorbent N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron-beam irradiation. The maximum capacity reaches 3.7 mmol/g using a mixture of the appropriate sulfates at pH 4.5. The selectivity of copper sorption is 80%. The structure of the coordination sphere of the copper complexes with N-(2-carboxyethyl)chitosan was investigated by ESR spectroscopy. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 635–639, September–October, 2008.     

Protolytic properties and complexation with copper(II) ions of some azo derivatives of β-arylaminopropionic acids

The azo coupling reaction of N-(2-carboxyethyl)anthranilic acid and N,N,N′,N′-tetrabis(2-carboxyethyl)-1,3-phenylenediamine with diazosulfanilic acid yielded the complexones sodium 4-N-(2-carboxyethyl)amino-5-carboxyazobenzene-4′-sulfonate (I) and 2,4-N,N,N′,N′-tetrabis(2-carboxyethyl)diaminoazobenzene-4′-sulfonic acid (II), respectively. The acidity constants of I and II (20°C, μ = 0.1M KCl) were determined to be as follows: for I, pK ₀₀ = 1.29 ± 0.13, pK ₀ = 2.92 ± 0.07, pK ₁ = 3.92 ± 0.05, pK ₂ = 5.16 ± 0.03; for II, pK ₀₀ = 2.35 ± 0.06, pK ₀ = 2.81 ± 0.09, pK ₁ = 3.21 ± 0.11, pK ₂ = 3.81 ± 0.09, pK ₃ = 4.34 ± 0.04, pK ₄ = 5.03 ± 0.06, pK ₅ = 6.67 ± 0.07. The electronic absorption spectra of I and II were measured, and acid-base equilibrium scheme for I and II in aqueous solutions were suggested. The complexation constants of I and II with copper(II) ions were determined to be logK _CuQ^I= 5.47 ± 0.06 and logK _CuQ^II= 5.72 ± 0.13 (20°C, μ = 0.1 M KCl).     

Synthesis in a gel as a new procedure for preparing carboxyethyl chitosan

A fundamentally new procedure of synthesis of carboxyethyl chitosan in a physical gel, ensuring higher degree of substitution at lower temperatures and lower consumption of time and chemicals, compared to the existing procedures, was developed. The structure of the resulting products was examined by diffuse reflection IR and ¹H NMR spectroscopy in solutions and also ¹H and ⁷Li broad line NMR.     

Synthesis and structure of the disc-like cluster C72H102N12Ni13O40

The disc-like cluster C₇₂H₁₀₂N₁₂Ni₁₃O₄₀ is first time synthesized based on N-(2-pyridyl)methyliminodipropionic acid. Single crystal X-ray diffraction is used to determine its atomic structure. The cluster consists of seven-nuclear core: nickel(II) hydrocomplex (Ni...Ni distance 3.012–3.032 Å) and six nickel chelates of the corresponding acid arranged around its perimeter (Ni...Ni distance 2.981–3.164 Å). In the chelate part of the complex, the ligand is pentadentate owing to the formation of a bridging bond, thus organizing a coordination geometry of the metal center as a distorted square bipyramid (4+2). Liquid chromatography-mass spectrometry is employed to study the structure of the obtained nickel(II) complexes.     

Imidazole-containing chitosan derivative: a new synthetic approach and sorption properties

A novel method for the synthesis of a hetaryl-containing chelate amino polymer, namely, N-(4(5)-imidazolylmethyl)chitosan (IMC), with a degree of substitution up to 0.3 was proposed. The “synthesis in gel” approach involves direct substitution of the hydroxyl group in 4(5)-imidazolylmethanol. The structures of these polymers were confirmed by ¹H NMR data. For sorption studies, IMC samples were crosslinked with epichlorohydrin and diglycidyl ethers of ethylene glycol and diethylene glycol. The degrees of swelling and sorption properties of the polymers largely depend on the crosslinking agent and the degree of crosslinking. The sorption capacities of IMC for Au^III, Pt^IV, and Pd^II ions are higher than those of the nonmodified polymer. The extraction of noble metal ions from chloride solutions becomes more selective with increasing degree of crosslinking. The sorption capacity of IMC for Co^II and Ni^II ions is higher than those of chitosan and its known N-heterocyclic derivatives.     

Comparative coordination ability of N-(2-hydroxyethyl)aminoacetic acid and O-(2-hydroxyethyl)hydroxyacetic acid in the copper(II) complexes

Copper(II) complexes based on N-(2-hydroxyethyl)aminoacetic and O-(2-hydroxyethyl)hydroxyacetic acids were synthesized. Their structures were studied by X-ray diffraction analysis. The coordination spheres of the copper metal center were compared in the condensed phase for the both ligands.