F. M. Chyragov

Photometric determination of copper(II) in nickel alloys using azoderivatives of ethyl acetoacetate

Abstract1-Ethoxy-2-(2-hydroxy-3-sulfo-5-chlorophenylazo)butane-1,3-dion (L1), 1-ethoxy-2-(2-hydroxy-3,5-disulfophenylazo)butane-1,3-dion (L2), 1-ethoxy-2-(2-hydroxy-4-nitrophenylazo)butane-1,3-dion (L3), and 1-ethoxy-2-(2-hydroxyphenylazo)butane-1,3-dion (L4) were synthesized on the basis of ethyl acetoacetate, and their analytical characteristics were studied. The following dissociation constants of the reagents were determined by potentiometric titration: pK1 = 5.94 ± 0.04 and pK2 = 9.75 ± 0.04 (L1), pK1 = 5.78 ± 0.02 and pK2 = 9.55 ± 0.03 (L2), pK1 = 6.03 ± 0.03 and pK2 = 9.86 ± 0.05 (L3), and pK1 = 6.19 ± 0.05 and pK2 = 9.98 ± 0.06 (L4). The chemical analytical characteristics of copper(II) complexes of L1–L4 were determined by spectrophotometry. It was found that, with an increase in the elecrophilic properties of the substituents introduced into the aromatic ring of the molecule, the sensitivity of the reaction increased; the substituents had no effect on the ratio of Cu : L = 1 : 2. A photometric procedure was developed for determining copper in nickel-based alloys.

Complexation of copper(II) with 3-(2-hydroxyphenylazo)pentadione-2,4

It is shown that 3-(2-hydroxyphenylazo)pentadione-2,4 (H2L) can exist in three tautomeric forms (enol-azo, keto-azo, and hydrazo). The effective atomic charges in the tautomeric forms of H2L are calculated by the Hückel MO LCAO method. The molar fractions and molar absorptivities of the tautomers at different pH are found. The complexation of copper(II) with H2L is studied by spectrophotometry. Beer’s law is obeyed for 0.51–5.12 µg/mL of copper. The assumed complex structure is given. The effect of foreign ions and masking agents on the complexation is studied. A procedure for the photometric determination of copper(II) in zinc-based alloys is proposed.

Quantum-chemical calculations of the tautomeric forms of 3-phenylazopentane-2,4-dione and the thermodynamic parameters of complexation between its isomers and some metals in aqueous ethanol

MO LCAO calculations in the Hückel approximation of the tautomeric (azo enol, oxo azo, and hydrazo) forms of 3-phenylazopentane-2,4-dione (L) revealed that the oxo azo tautomer is most reactive. The effective charges at the atoms of all the tautomers were calculated. Complexation between some metals and L in aqueous ethanol was studied by potentiometric and conductometric titration. The potentiometric data were used to calculate the standard thermodynamic functions of the complexation.

Complexation of copper(II) with azo derivatives of benzoylacetone

Abstract1-Phenyl-2-[2-hydroxy-3-sulfo-5-nitrophenylazo]butadione-1,3 (H2L) was synthesized from benzoylacetone. The dissociation constants of the reagent were determined (pK1 = 4.98 ± 0.03 and pK2 = 8.53 ± 0.01). Stability constants of some metal complexes with this reagent were determined by potentiometric and conductometric titrations. The stability of these complexes decreased in the following order: Fe > Cu > UO2 > Ni > Co > Zn > Cd > Mn > Mg > Ca. The copper(II) H2L complex with a stoichiometry of 1: 2 was studied by photometry. ε = 1.4 × 104, Beer is law was obeyed in the copper concentration range from 0.25 to 3.07 μg/mL. The effect of foreign ions and masking agents on complexation was studied. A procedure for the photometric determination of copper(II) in seawater was developed.

Thermochemical characteristics of complexation of some ions with 3-(4-bromophenylazo)pentane-2,4-dione in aqueous ethanol

The potentiometric and conductometric titration was used to study complexation between some metal ions and 3-(4-bromophenylazo)pentane-2,4-dione (L) in aqueous ethanol. The standard thermodynamic characteristics of the complex formation reaction were determined. The effective atomic charges in the tautomeric forms of L (azo enol, azo keto, hydrazo) were calculated by MO LCAO quantum-chemical method in the Hückel approximation.

Bis-(2,3,4-trihydroxyphenylazo)benzidine as a reagent for the photometric determination of aluminum

The complexation of aluminum(III) with bis-(2,3,4-trihydroxyphenylazo)benzidine is studied in the presence of urotropine, phenanthroline, 2,2′-dipyridyl, and papaverine. The optimal conditions are found for complexation. The molar absorption coefficients and stability constants of the aluminum complexes are determined. The concentration range is found in which Beer’s law is obeyed. A procedure for the photometric determination of aluminum in zinc-based alloys is proposed.

Thermodynamic characteristics of metal complexation with 3-[4-iodophenylazo]-2,4-pentanedione in an aqueous ethanol solution

AbstractComplexation of metals with 3-[4-iodophenylazo]-2,4-pentanedione (L) in an aqueous ethanol solution at temperatures 298 ± 0.5, 318 ± 0.5, and 318 ± 0.5 K has been studied by the potentiometric titration method. The standard thermodynamic functions of the complexation reaction have been found. They change in the following sequence:

Determination of uranium(VI) in natural waters after preconcentration on adsorbent containing m-aminophenol fragments

\begin{gathered} \left| {\Delta G^0 } \right|:Fe > Cu > Ni > Co > Mn > UO_2 > Zn > Cd > Mg > Ca, \hfill \\ \left| {\Delta H^0 } \right|:Fe > Cu > UO_2 > Ni > Co > Zn > Cd > Mn > Mg > Ca, \hfill \\ \Delta S^0 :Ca > Mn > Mg > Cd > Co > Ni > Zn > Fe > Cu > UO_2 . \hfill \\ \end{gathered}