Thermodynamic characteristics of the protolytic equilibria of tetramethylenediamine-N,N,N′,N′-tetraacetic acid

The stepwise dissociation constants of tetramethylenediamine-N,N,N′,N′-tetraacetic acid (H₄L) are determined by means of potentiometry at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO₃). The heat effects of the dissociation of the betaine groups of the complexone are measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H₄L are calculated via combined use of the results from thermochemical and potentiometric studies performed under identical experimental conditions. Our results are compared with the corresponding data on relative compounds.     

Thermodynamic characteristics of protolytic equilibria of trimethylenediamine-<Emphasis Type="Italic">N,N,N′,N′</Emphasis>-tetraacetic acid

The thermal effects of the neutralization of betainic protons of trimethylenediamine-N,N,N′,N′-tetraacetic acid (H₄L) at 298.15 K and ionic strength of 0.3, 0.5, and 1.0 (KNO₃) were directly measured by calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H₄L were calculated from a combination of thermochemical and potentiometric data obtained under identical experimental conditions. The results obtained were compared with the corresponding data for related compounds taking into account the specific structure of diamine complexones.     

Thermodynamic characteristics of the acid–base equilibria of ethylenediamine-N,N′-diglutaric acid in aqueous solutions using calorimetric data

Russian Journal of Physical Chemistry A - The enthalpies of reaction of betaine group neutralization of ethylenediamine-N,N'-diglutaric acid (H4L) at 298.15 K and at different values of ionic...     

Protolytic equilibria of N-(β-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid

The heats of the successive dissociation of N-(β-hydroxyethyl)ethylenediamine-N,N′, N′-triacetic acid at T = 298.15 K and I = 0.1, 0.5, and 1.0 (KNO₃) have been determined directly by calorimetry. Standard thermodynamic characteristics of the protolytic equilibria have been derived from thermochemical and potentiometric data obtained under identical conditions. The results are compared with the corresponding data for similar compounds and are discussed with reference to the structural features of the diamine chelants.     

Synthesis and crystal structure of a 2-D yttrium coordination network with propylenediamine-N,N,N′,N′-tetraacetic acid

A 2-D binuclear coordination polymer, {[Y^III(Hpdta)(H₂O)]_2?·?6H₂O} _n (H₄pdta?=?propylenediamine-N,N,N′,N′-tetraacetic acid), has been synthesized through direct hydrothermal reaction and characterized by infrared spectrum and thermal analysis. Single-crystal X-ray diffraction reveals that Y(III) is eight-coordinate of almost standard square antiprismatic polyhedron.     

Cyclopalladation of N,N,N′,N′-tetramethylisophthalthioamide

Summary N,N,N,N-Tetramethylisophthalthioamide (Hmpt) was cyclopalladated with PdCl₂ in hot dimethylsulphoxide to give [PdCl(mpt)]. The structure was determined by X-ray analysis. The thioamide is metallated at C(2) to act as an S528-01C528-02S tridentate anionic ligand. There is appreciable steric repulsion between the benzene ring H(4, 6) and the dimethylamino groups. The hydrogens and the methyl groups mutually deviate from the coordination plane in opposite directions. The stability of the fused 5,5-membered chelate ring formed by the S528-03C528-04S ligand seems to overcome the steric hindrance. Derivatives were prepared by replacement of the chloride ion with iodide, diethyldithiocarbamate, 4-tert-butylpyridine, or tri-n-butylphosphine, and characterized spectroscopically. The S528-05C528-06S-fused chelate ring was maintained in these derivatives.     

Solvent extraction of uranyl by N,N,N′,N′-tetraoctylsuccinylamide from nitric acid solution

Synthesis and characterization of N,N,N′,N′-tetraoctylsuccinylamide (TOSA) was carried out and used for extraction of U(VI) from nitric acid solutions. The effect of different factors affecting the extraction distribution ratio (TOSA concentration, concentrations of nitric acid, salting-out agent LiNO₃ concentration, equilibration time, temperature and effect of diluents) have been investigated. The results obtained indicated that TOSA have a great capability to extract uranyl with kerosene-1,3,5-trimethylbenzene than other diluents, it have a high extraction distribution ratios when the concentration of TOSA is lower and not found the third matter. It was found that the main extracted species is UO₂(NO₃)₂·TOSA. The apparent equilibrium constant of extraction determined is (2.32 ± 0.31) L³/mol³ at (298 ± 1) K. The enthalpy of extraction is ?35.20 ± 0.352 kJ/mol.     

Extraction behavior of strontium from nitric acid solution with N,N,N′,N′-Tetraisobutyl diglycolamide

The extraction behaviors of strontium from nitric acid solution were investigated with N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA). Effects of acidity, diluents, concentration of extractant and temperature on the distribution ratio of strontium (D _Sr) were examined. The stoichiometry of the extracted molecule was Sr²⁺:TiBDGA of 1:3. The apparent extraction equilibrium concentration constant logK _ex was 3.25. The enthalpy change ΔH and entropy change ΔS were ?55.6 kJ mol^-1 and ?124 J mol^-1 K^-1, respectively. The extraction is an exothermic process. Through two strip stages, strontium could be stripped effectively by 0.01 M nitric acid solution.     

Thermodynamics of nickel(II) complexing with trimethylenediamine-<Emphasis Type="Italic">N,N,N′,N′</Emphasis>-tetraacetic acid

The heats of nickel(II) trimethylenediaminetetraacetate formation were determined by direct calorimetry at 298.15 K and ionic strength I =0.1, 0.5, and 1.0 (KNO₃). The corresponding thermodynamic characteristics were calculated. The results were compared to literature data on the related compounds.     

Thermodynamic characteristics of acid–base equilibria of glycyl-glycyl-glycine in water–ethanol solutions at 298 K

The enthalpies of the acid dissociation of glycyl-glycyl-glycine zwitterions and triglycinium ions are determined calorimetrically in water–ethanol solvents containing 0.0, 0.10, 0.30, and 0.50 molar fractions of ethanol at ionic strengths of 0.1 (maintained by sodium perchlorate) and Т = 298.15 K. It is found that increasing the ethanol content in the solvent enhances the endothermic effect of triglycinium ion dissociation and reduces the endothermic effect of glycyl-glycyl-glycine dissociation. The results are discussed in terms of the solvation thermodynamics.     

A New Dinuclear Gadolinium Complex Constructed from p-Phenylenediamine-N,N,N′,N′-tetraacetic Acid and in situ Generated Oxalate

Routine solution reaction of Gd3+ and p-phenylenediamine-N,N,N′,N′-tetraacetic acid (p-PhDTA) yields a dinuclear complex [Gd2(ox)(p-PhDTA)2(H2O)10]·6H2O (ox = oxalate), which was characterized by single-crystal X-ray diffraction (MoKα radiation, = 0.71073), elemental analysis and IR. This complex crystallizes in the monoclinic system, space group P21/n with a = 10.2522(8), b = 10.0053(8), c = 23.8834(18), = 99.1080(10)°, V = 2419.0(3)3, Z = 2, Mr = 1367.32, Dc = 1.877 g/cm3, F(000) = 1368, = 2.830 mm-1, the final R = 0.0337 and wR = 0.0794 for 4747 observed reflections (I > 2 (I)). The exo-tetradentate oxalate ligand, generated in situ from the oxidative coupling of methanol, is incorporated to construct a dinuclear Gd2(ox)2 unit decorated with p-PhDTA ligands on the two sides with a monodentate coordination mode. The dinuclear molecules are further connected by the lattice water molecules to form a three-dimen- sional hydrogen network.     

Sensitive Spectrophotometric Determination of Benzoylperoxide with N,N,N′,N′-Tetramethyl-p-phenylenediamine

Abstract

A highly sensitive spectrophotometric determination of benzoylperoxide (BPO) based on the color developing reaction between N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) and BPO in the presence of cerium(IV) in weakly acidic media is proposed. The calibration graph is linear in the range 0–6000 ng BPO per 10 ml with an apparent molar absorptivity of 4.73 × 10⁵ 1 mol^?1 cm-1 at 612 nm. The proposed method is about 50-fold more sensitive than N-ethyl-2-naphthylamine (NENA), and application to assays of flour is described.     

Vibrational spectra of N,N-dimethyl/diethylaniline,N,N,N′,N′-tetramethyl/tetraethyl-p-phenylenediamine and N,N,N′,N′-tetramethyl/tetraethylbenzidine derivatives

The ground state and protonated state (quaternized salt) vibrational spectra (200–1800 cm⁻¹) of the title amines are reported for various ring and/or methyl deuterated derivatives. Complete assignments are proposed and compared to those established for the parent hydrocarbons, benzene and biphenyl, and for the parent primary amines, aniline, p-phenylenediamine and benzidine. The electronic distribution, N(n)→ring(π) charge-transfer character and inductive effects are characterized from a vibrational point of view. Finally changes in the vibrational and electronic conformation upon protonation of the nitrogen atom are discussed. These results provide a fundamental basis for the vibrational investigation of excited states and reactive transients of aromatic amines.     

The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids

The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0 (KNO₃) were determined potentiometrically. The results were extrapolated to zero ionic strength by the equation with one individual parameter. The thermodynamic constants of dissociation were calculated. The results are compared with the corresponding data on related compounds.     

Calorimetric study of the reaction between formic acid and N,N,N′,N′-tetramethylethylenediamine from the aspect of thermal energy storage

The attack by formic acid on the nitrogen electron pairs of N,N,N,N-tetramethylethylenediamine leads to the stoichiometric salt or to many other complexes with different molar fractions. Physical and thermodynamic parameters of two adducts, obtained by calorimetric study, are discussed in terms of their use as potential phase change materials in thermal energy storage because of their large heat of fusion between 288 and 333 K.

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Zusammenfassung Bei der Einwirkung von Ameisensäure auf die Elektronenpaare von N,N,N,N-Tetramethylethylendiamin entsteht ein stöchiometrisches Salz oder mehrere andere Komplexe mit unterschiedlichem Molenbruch. Es werden physikalische und thermodynamische Parameter zweier bei der kalorimetrischen Untersuchung erhaltenen Addukte hinsichtlich ihrer Verwendung als potentielle Phasenwechselsubstanzen bei der thermischen Energiespeicherung diskutiert, da sie im Bereich 288–333 K eine große Schmelz-wärme besitzen.