Temperature Coefficient Method Research Articles

ON THE INTERACTION OF H[AuCl2] WITH 2-ETHYLIMIDAZOLE INTERACTION OF [AuCl2]- WITH 2-ETHYLIMIDAZOLE AT 278-318K

Using the potentiometric titration method, the process of complexation of gold (I) with 2-ethylimidazole was studied. Adding an organic ligand solution to the [AuCl2]-/Au system leads to a smooth decrease in the electrode potential (without any jumps). The nonlinearity of the dependence of E on –log[2EI] indicates the stepwise nature of complex formation between [AuCl2]- and 2-ethylimidazole. The general stability constants of successively formed complexes were determined in the temperature range 278-318K (at T=298K, logβ1=4.41±0.03; logβ2=10.81±0.02). An increase in temperature leads to the stability of the formed complexes. It has been shown that trivalent gold complexes are superior in stability to similar gold(I) complexes. The thermodynamic functions of the process of complex formation of gold (I) with 2-ethylimidazole were calculated using the temperature coefficient method. The value of enthalpy (∆Н0) was determined by the tangent of the slope of the direct dependence logβί0=f(1/T), the value of entropy (∆S0) by the segment cut off by this straight line on the ordinate axis, while the change in the isobaric-isothermal potential was calculated according to the equation ∆G0 =∆H0-T∆S0. It was revealed that the replacement of chloride ions with the ultraspherical molecule of 2-ethylimidazole is accompanied by a positive change in enthalpy. This experimental fact is associated with the difference in the binding energies of gold-chlorine (Au-Cl) and gold-2-ethylimidazole (Au-2-EI). A positive change in enthalpy makes a negative contribution to the spontaneous occurrence of complexation reactions. At the same time, the value of ∆S0 for the studied system has a positive value. In the [AuCl4]- –2-EI-H2O system, the number of particles participating in the complexation reaction remains unchanged. The positive change in entropy is most likely due to the release of the H2O molecule from the hydration shell of each of the reactants. A positive change in entropy promotes the spontaneous occurrence of complexation reactions in the studied system.

Temperature Effect on the Acid–Base Properties of β-Alanine in Aqueous Solution

The acid–base properties of β-alanine (β-Ala) in aqueous solution were studied by the pH-metric method in the temperature range 278.2–318.2 K and at I = 0.1 M KCl. The ionization constants (pKi) of β‑Ala at different temperatures were calculated. The ionization constants were found to change depending on the temperature: an increase in the temperature leads to a decrease in pKi for both carboxyl and amine groups, which indicates that the degree of ionization of β-alanine increased and its acidic properties were enhanced. The thermodynamic characteristics (ΔН0, ΔS0, and ΔG) of the corresponding ionization processes were determined by the temperature coefficient method.

COMPLEX FORMATION OF GOLD (I) WITH 2-METHYLIMIDAZOLE

The complex formation process of Au (I) with 2-methylimidazole was studied by potentiometric titration. When 2-methylimidazole is added to the [AuCl2]-/Au system, the potential gradually decreases without any jumps. The nonlinearity of the dependence of E on –lg[2MI] indicates the stepwise nature of the complex formation between [AuCl2]- and 2-methylimidazole. The general and thermodynamic stability constants of the complexes were determined in the temperature range of 278-318 K (at T=298 K, lgβ0[AuСl(Н2МИ)]+=13.84±0.03; lgβ10[Au2МИCl]=5.38±0.05; lgβ20[Au(2МИ)2]+=10.60±0.03). The reliability of the determination of the constants is proved by the satisfactory agreement between the experimentally found values of the potentials (Eex.) with theoretical ones (Etheor.). As the temperature increases, the stability of the complexes increases. A change in the ionic strength of the solution has little effect on the stability of the complexes. Comparison of the process of complexation of gold (I) and gold (III) with 2-methylimidazole shows that the stability of the complexes of trivalent gold is superior to similar complexes of gold (I). The thermodynamic functions of the complex formation reaction were calculated by the temperature coefficient method. In this case, the value of ΔrН0 was determined from the tangent of the slope of the direct dependence lgβ0=f(1/T), and the value of ΔrS0 was determined from the segment cut off by this straight line on the y-axis. The change in the isobaric-isothermal potential was calculated by the equation ΔrG0= ΔrН0-TΔrS0. The substitution of chloride ions for a 2MI molecule is accompanied by a positive change in ΔН, which has a negative contribution to the spontaneous course of reactions. For the [AuCl2]- - 2MI system, the number of particles participating in the reaction remains unchanged and the positive change in ΔS is most likely due to the release of water molecules from the hydration shell of the initial substances and reaction products.

Complex formation of molybdenum (V) with 1-phenyl-2,3-dimethylpyrazoline-5-thion in 4 mol/L HCI medium at 273-338 K

The process of complexation of molybdenum (V) with 1-phenyl-2,3-dimethylpyrazolin-5-thione in a 4 mol/l HCI medium in the temperature range 273-338 K was studied by the potentiometric method. It has been shown that the reduced form of the 1-phenyl-2,3-dimethylpyrazolin-5-thione molecule is involved in the complex formation reaction. Using the data of potentiometric studies, the change in the energy value (ΔE) of the (NH4)2[MoOCI5]2-1-phenyl-2,3-dimethylpyrazolin-5-thione-4 mol/l HCl system, the equilibrium concentrations of 1-phenyl-2,3-dimethylpyrazolin-5-thione, formation function values, step and general stability constants of oxochloro-1-phenyl-2,3-dimethylpyrazolin-5-thione complexes of molybdenum (V) formed in HCl solutions in the temperature range 273-338 K. The stability constants of oxochloro-1-phenyl-2,3-dimethylpyrazolin-5-thione complexes of molybdenum (V) were refined using the Bjerrum graphical method. The temperature coefficient method was used to estimate the thermodynamic functions of complex formation processes in the (NH4)2[MoOCI5]-1-phenyl-2,3-dimethylpyrazolin-5-thione - 4 mol/L HCI system. The domains of dominance and the maximum yield of each complex form are found. It has been established that in the studied system (NH4)2[MoOCI5]-1-phenyl-2,3-dimethylpyrazolin-5-thione - 4 mol/l HCI during the interaction of the MoO3+ ion with 1-phenyl-2,3-dimethylpyrazolin- 5-thione in the entire temperature range of the experiment forms 5 mononuclear coordination compounds containing from one to five coordinated molecules of the organic ligand. It was found that with increasing temperature, the values of the general stability constants of coordination compounds decrease, which confirms the exothermicity of the reaction of formation of oxochloro-1-phenyl-2,3-dimethylpyrazoline-5-thione compounds of molybdenum (V). The experimentally found values of enthalpy made it possible to assume that the reaction of complex formation between the MoO3+ ion and the molecules of nitrogen- and sulfur-containing heterocyclic 1-phenyl-2,3-dimethylpyrazolin-5-thione proceeded exothermically spontaneously. Based on the above equations, all calculations were carried out using a computer in the Excel programming language, Borland Delphi, Windows 7 operating system.

Potentiometer study of the process of complexation of silver (I) ions with thiourea

The process of complexation of silver(I) ions with thiourea (Tu) in the temperature range 287.16–318.16 K at an ionic strength of 0.11 M (I = 0.1 NaNO3 + 0.01 HNO3) was studied by the potentiometric method using a silver electrode in aqueous solution. The study was performed at a concentration of silver(I) ions CAg+ = 1 · 10–5 and CAg+ = 1 · 10–3 M. The values of the stability constants of AgTui + complexes (i = 1–2) were estimated at CAg+ = 1 · 10–5 M. The AgTu3+ complex constant was determined at CAg+ = 1 · 10–3 M and CTu ≥ 0.01 M. The stability constants of complexes were calculated using the Leden method. The values of the complex constants at 298.16 K are equal to: lgβ1 = 5.59 ± 0.10 (AgTu+), lgβ2 = 10.62 ± 0.03 (AgTu2+) and lgβ3 = 13.05±0.11 (AgTu3+). It is established that the temperature effect does not affect the number of formed particles in the solution; an increase in temperature leads to a decrease in the stability of complexes. The analysis of the values of the stability constants by degrees shows that the step constants AgTu3+ (AgTu2+ + Tu = AgTu3+ + lgβ3 = 2.4) are much smaller than the constants for mono- and bis-coordinated complexes. The complexes thermodynamic parameters (ΔH0, ΔG0, ΔS0) were calculated by the temperature coefficient method. In the system under study, all complexation reactions are exothermic. The largest increase in the value of enthalpy (ΔH0) is observed in the formation of a complex containing two molecules of thiourea. The change in entropy (ΔS0) at the stage of formation of bis- and tris-coordinated complexes is negative, which is most likely due to a decrease in the number of particles in the system under study. It is determined that enthalpy-entropy dependences show a monotonic character. The spontaneous course of complexation reactions is determined by the value of the free Gibbs energy (ΔG0). In degrees G0 decreases (ΔG0)1 < (ΔG0)2 < (ΔG0)3) and has a negative value, which indicates a decrease in the affinity of the complexing agent to the ligand.

COMPLEXATION OF GOLD (III) WITH 1-FURFURYLIDENE AMINO-1,3,4-TRIAZOLE AT 288 – 318 K

The potentiometric titration method was used to determine the ionization constant of 1-furfurylideneamino-1,3,4-triazole (pKk = 11.83 log.). The dominating region of 1-furfurylideneamino-1,3,4-triazoles (FF) was identified in a wide pH range. It was shown that 1-furfurylideneamino-1,3,4-triazole ion (HL+) predominates in the pH range up to 0.5-2.0. At pH of 5.0 to 10.5, the neutral molecule (L) predominates, and at pH>13.0 1-furfurylideneamino-1,3,4-triazolate ion (L-) predominates in a solution. To determine the number of a particles formed during the interaction of Au (III) with FF from the potentiometric titration data the dependence of ΔE on -lg [FF] was used for 1-furfurylideneamino-1,3,4-triazole gold (III) complexes at 288-318 K. The slope of the curves of the ΔE-lg [FF] with the excess of 1-furfurylideneamino-1,3,4-triazole at temperatures of 288, 298 and 308 K is 0.059, 0.060 and 0.061 V/mol/l-1, which corresponds to the sequential addition of three molecules of 1-furfurylideneamino-1,3,4-triazole to gold (III). At the temperature of 318 K it is not possible to find the slope angle corresponding to the tris complex due to a quick change in the potential with an excess of FF in a solution. General stability constants of 1-furfuryldenoamino-1,3,4-triazole complexes of Au (III) according to potentiometric titration data was determined by the Friedman method and non-linear least squares method. It was shown that as the temperature increases, the general stability constants of gold (III) complexes are reduced. It was shown that the introduction of substituents into the 1,2,4-triazole molecule affects both the number of particles formed in a solution and the stability of the complexes. Thus, in the system Au (III) -1,2,4-triazole-H2O at 298 K four complex particles are formed, and in the Au (III) system, 1-furfurylideneamino-1,3,4-triazole-H2O only three are formed. The general stability constants of 1,2,4-triazole complexes equal to lgβ1 = 6.56, lgβ2 = 11.13, lgβ3 = 14.94 and lg4 = 18.78 log units, and for 1-furfurylideneamino-1,3,4-triazole complexes Igβ1 = 5.92, lgβ2 = 10.14, lgβ3 = 13.80 log units. The thermodynamic functions of complexe formation were calculated by the temperature coefficient method. It was shown that all complex particles are enthalpy-stabilized. The greatest increase in the exothermicity of the reactions is observed when a complex of three organic-ligand molecules is formed. The value of ΔS at all steps of complexation is negative, which is most likely due to the decrease in the number of particles in a system under study. The spontaneous reaction of complexation is determined by the enthalpy factorFor citation:Safarmamadov S.M., Muborakkadamov D.A., Mabatkadamova K.S. Complexation of gold (III) with 1-furfurylidene amino-1,3,4-triazole at 288 – 318 K. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 37-43.

Zero Temperature Coefficient Bias in MOS Devices. Dependence on Interface Traps Density, Application to MOS Dosimetry

In this paper the influence of temperature fluctuations on the response of thick gate oxide metal oxide semiconductor dosimeters is reviewed and the zero temperature coefficient (ZTC) method is evaluated for error compensation. The response of the ZTC current to irradiation is studied showing that the error compensation impoverishes with absorbed dose. Finally, an explanation and analytic expression for the shifts in the ZTC current with irradiation based on the interface traps creation is proposed and verified with experimental data.

Solvent extraction studies of plutonium(IV) by crown ether dicyclohexyl-18-crown-6 (DC18C6) in 1-butyl-3-methyl imidazolium hexafluorophosphate (C4mimPF6) and 1-hexyl-3-methyl imidazolium hexafluorophosphate (C6mimPF6) room temperature ionic liquids (RTIL)

Abstract Solvent extraction studies of Pu(IV) from aqueous nitric acid by crown ether (CE) dicyclohexyl-18-crown-6 (DC18C6) in 1-butyl-3-methyl imidazolium hexafluorophosphate (C4mimPF6) and 1-hexyl-3-methyl imidazolium hexafluorophosphate (C6mimPF6) room temperature ionic liquids (RTIL) were carried out at different temperatures in the range of 298 to 318 K. The least squares analysis of the extraction data indicated the extracted species at 1 M HNO3 aqueous concentration to be cationic complex with the formula Pu(CE)(NO3)2 2+. The thermodynamic parameters evaluated by the temperature coefficient method indicated that the reaction is favoured by decrease in enthalpy and is counteracted by decrease in entropy.

ChemInform Abstract: Complexation and Thermodynamics of the Uranyl Ion with Phosphate.

Abstract Complexation of UO22+ with the H2PO4− anion at various ionic strengths (0.1–1.0 M NaClO4) has been studied using the solvent extraction technique. The equilibrium constants (β1 and β2) for the formation of the species UO2H2PO4+ and UO2(H2PO4)2 were fit to the following extended Debye-Huckel expressions: logβ 1 (I) = 3.47 − 2.044I 1/2 1+1.6I 1/2 + 0.273I and logβ 2 (I) = 5.77 − 3.066I 1/2 1+1.6I 1/2 + 0.364I . The thermodynamic parameters for these systems have been computed using the temperature coefficient method. The reactions are favoured by entropy and opposed by enthalpy. The complexes are predominantly the “inner sphere” type.

Thermodynamics of neptunium(V) complexes with phosphate at elevated temperatures

The complexation of Np(V) with phosphate at elevated temperatures was studied by a synergistic extraction method. A mixed buffer solution of TRIS and MES was used to maintain an appropriate pH value during the distribution experiments. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of phosphate were increased. Stability constants of the 1:1 and 1:2 Np(V)-HPO4 2− complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [HPO4 2−] on the distribution ratio. The thermodynamic parameters including enthalpy and entropy of complexation between Np(V) and HPO4 2− at 25 °C–55 °C were calculated by the temperature coefficient method.

Solvent extraction studies on Th(IV) and U(VI) using PolyEthylene Glycol (PEG) based aqueous biphasic system (ABS) with 18-crown-6

SummaryExtraction of Th(IV) and U(VI) using PEG-2000/(NH4)2SO4(40% w/w of each) aqueous biphasic system (ABS) with 18-crown-6 (18-C-6) as the extractant was studied at four fixed temperatures in the range 288 to 318 K. The species extracted were identified to be [Th·(18-C-6)](SO4)2and [UO2·(18-C-6)]SO4by the slope ratio method. The equilibrium constant (K) was evaluated for the extraction reactions. The thermodynamic parameters evaluated by the temperature coefficient method at 298 K showed that the reaction is favoured by decrease in enthalpy and counteracted by decrease in entropy. The large decrease in the enthalpy values was attributed to direct bonding of crown ether to the central metal atom (i.e.the formation of inner sphere complex).

EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH4NO3, NH4SCN, NH4ClO4 or a mixture of 0.3 M NH4NO3 + 0.7 M NH4ClO4 at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML3 · 3CMPO (M = Am(III) or Eu(III), L = NO3 −, SCN− or ClO4 −) and M(NO3)(ClO4)2 · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The −ΔG values follow the order SCN− > NO3 − + ClO4 − > NO3 − ≈ ClO4 −, whereas the −ΔH values an order NO3 − + ClO4 − > SCN− > NO3 − ≈ ClO4 −. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.

Kinetics and mechanism of the acid dissociation of the Cobalt(II) complex of novel C‐functionalized 13‐membered macrocyclic dioxotetraamines

The kinetics of acid dissociation of cobalt(II) complexes of novel C-functionalized 13-membered macrocyclic dioxotetraamines was studied using stopped-flow spectrophotometry at different temperatures. The results indicated the dissociation rate follows the law vd = CcomkK1K2[H]2/(1 + K1[H] + K1K2[H]2). On the basis of the experiment facts obtained, the dissociation kinetics is interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-rate-determining step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in strongly acidic solution. K1 and K2 of the pre-rate-determining steps and k of the rate-determining step were obtained by means of non-linear least-squares fitting method, and corresponding activation parameters were also obtained by means of temperature coefficient method. The influence of the substituents to the acid dissociation rates has been discussed. The Brönsted type linear-free energy relationship does exist in these C-functionalized dioxotetraamine cobalt(II) complexes. It is first found that the linear relationship between the ΔH≠ and ΔS≠ of the rate-determining step does exist in this and another analogous system. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 804–809, 1999

Kinetics and mechanism of the acid dissociation of the Cobalt(II) complex of novel C-functionalized 13-membered macrocyclic dioxotetraamines

The kinetics of acid dissociation of cobalt(II) complexes of novel C-functionalized 13-membered macrocyclic dioxotetraamines was studied using stopped-flow spectrophotometry at different temperatures. The results indicated the dissociation rate follows the law vd = CcomkK1K2[H]2/(1 + K1[H] + K1K2[H]2). On the basis of the experiment facts obtained, the dissociation kinetics is interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-rate-determining step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in strongly acidic solution. K1 and K2 of the pre-rate-determining steps and k of the rate-determining step were obtained by means of non-linear least-squares fitting method, and corresponding activation parameters were also obtained by means of temperature coefficient method. The influence of the substituents to the acid dissociation rates has been discussed. The Bronsted type linear-free energy relationship does exist in these C-functionalized dioxotetraamine cobalt(II) complexes. It is first found that the linear relationship between the ΔH≠ and ΔS≠ of the rate-determining step does exist in this and another analogous system. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 804–809, 1999

Study of kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocyclic dioxotetraamines

The kinetics of the acid dissociation of copper(II) complexes of novel C-functionalized macrocyclic dioxotetraamines has been studied by means of a stopped-flow spectrophotometer. The acid dissociation rate follows the law V d = C com kK 1 K 2 H 2 /(1+ K 1 H+ K 1 K 2 H 2 ). From the experimental facts we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in the strongly acidic solution. By means of temperature coefficient method, Δ H φ , Δ S φ of the pre-equilibrium step and Δ H ≠, Δ S ≠ of the rate-determining step were obtained. The results of 13-membered macrocyclic dioxotetraamines have been discussed. The influence of the substituents to the acid dissociation rates has also been discussed. The Bronsted type linear free energy relationships do also exist in these C-functionalized dioxotetraamine copper(II) complexes.

Kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocylcic dioxotetramines

The kinetics of the acid dissociation of copper(II) complex of a novel C-functionalized macrocyclic dioxotetraamine has been studied using a stopped-flow spectrophotometer. It was provent that substituents decrease the acid dissociation rates. The dissociation rate follows the law v d = C com kK 1 K 2H 2/(1 + K 1H + K 1 K 2H 2). On the intermediates we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in strongly acidic solution. By means of temperature coefficient method, K 1, K 2 of the pre-equilibrium step and ΔH ≠ and ΔS ≠ of the rate-determining step were obtained and the results discussed. It is the strong in-plane ligand field that increased ΔH of the rate-determining step and thus decreases the dissociation rate constant. The Brönsted type linear free energy relationships do exist in this C-functionalized dioxotetraamine copper(II) complex. The results clarify insights into acid dissociation mechanisms for the 14-membered macrocyclic dioxotetraamine copper(II) complex.

Complexation Behavior of Heterocyclic Hydrazones. I. Structure and Acid-Base Equilibria for Heterocyclic Hydrazones

Abstract The acid-base equilibria of twenty-one hydrazones substituted by phenyl, pyridyl and/or quinolyl groups have been investigated in aqueous solutions over the region of H− to H0 acidity function by a spectrophotometric method at 25 °C. For 2-pyridinecarbaldehyde 2-(5-substituted)pyridylhydrazones, although the proton dissociation of the neutral species (HL) satisfied a Hammett correlation, those of H2L+ and H3L2+ did not. The thermodynamic parameters for the proton dissociations of H2L+ and H3L2+ of seven representative liqands were determined by a temperature-coefficient method at 25 °C and an ionic strength of 0.1 (KCl). The enthalpy and entropy changes for the proton dissociations of H3L2+ and H2L+ were influenced by the steric effects of the methyl group and/or the introduced quinolyl ring. An analysis of the pH dependence of the 1H NMR signals for three hydrazones in an acetone-d6–D2O solution gave more profitable information concerning the fine structures of HL, H2L+, and H3L2+. Each 1H and 13C NMR chemical shift of some ring-substituted methyl derivatives (HL form) in a dioxane–D2O solution has been briefly assigned. On the other hand, a single-crystal X-ray analysis, 1H NMR data in chloroform-d and thermodynamic data for di-2-pyridyl ketone 2-pyridylhydrazone (DPPH) suggested that the intramolecular hydrogen bond in the DPPH molecule is broken by the addition of a proton to the H2L+ species in an aqueous solution.

The thermodynamics of complexation of transition and lanthanide ions by 3-(α-carboxymethylaminobenzyli-denehydrazino)-5,6-diphenyl-1,2,4 triazine (HipHt)

The metal-ligand stability constants of the Ni(II), Co(II), Zn(II), Mn(II), Cd(II), Fe(III), UO 2(II) and Ln(III) chelates of HipHT were determined in 75% (v/v) dioxane-water medium at 10, 20 and 30°C and μ = 0.1M(KNO 3). The thermodynamic parameters for the proton-ligand and metal-ligand stability constants were obtained by the temperature coefficient method. The thermodynamic functions Δ G and Δ H of the complexes were analyzed in terms of the electrostatic (el) and non-electrostatic (non) components. The values of Δ H non and Δ H el show a linear variation with the hardness and softness E ν n of the metal ion and with the heat of hydration Δ H h, of the metal ion, respectively. HipHT behaves as a diprotic tridentate (NNO) donor towards the metal ions, as inferred from the infrared spectra of its metal chelates.

Extraction of actinides with tropolone

The partition coefficient of tropolone in xylene, dichloroethane and chloroform was determined from 0.05M HCl medium. The values obtained were 5.6, 25.5 and 43, respectively. In the extraction of UO 2 2+ using tropolone (HT) in xylene from an aqueous medium of ionic strength 0.05, the species UO2T2·HT was established. The species extracted in presence of a neutral donor was found to be UO2T2·S[S+dioctyl sulfide (DOS), dibutylhexanamide (DBHA), tri-n-butyl phosphate (TBP), dioctyl sulfoxide (DOSO), and tri-n-octylphosphine oxide (TOPO)]. The equilibrium constant of complex formation between the self-adduct and the neutral donor was calculated and was found to follow the basicity order (DOS«DBHA<TBP<DOSO»TOPO). The thermodynamic parameters of the adduct UO2T2·DOSO were also calculated by the temperature coefficient method. The values of free energy, enthalpy and entropy changes obtained were −1.26 kJ·mol−1, −1.98 kJ/mol and −2.5 J·mol−1·deg−1, respectively.

Extraction of uranium(VI) and plutonium(IV) with some aliphatic amides

Extraction of uranium(VI) and plutonium(IV) has been studied with N,N′-dibutyl derivatives of hexanamide (DBHA), octanamide (DBOA) and decanamide (DBDA) at various fixed temperatures of 20, 30, 40 and (50±0.1)°C. The equilibrium constants for the uptake of nitric acid (Kh, a measure of their relative basicities) by these amides were evaluated by the usual method. The equilibrium constants for the extraction of uranium as well as plutonium with all the three amides follow their order of basicity (Kh) viz. DBHA (0.09)<DBOA (0.10)<DBDA (0.13) with log K values of 1.31, 1.43 and 1.73 for uranium and 3.55, 3.65 and 4.17 for plutonium, respectively. It has been observed that whereas uranium(VI) is extracted as a disolvate (similar to TBP and sulfoxides), plutonium(IV) has been found to be extracted as a trisolvate. The thermodynamic parameters evaluated by the usual temperature coefficient method indicate that the extraction reactions of uranium as well as plutonium are stabilized by negative enthalpy change only.