Thermodynamics of substituted pyrazolone. V: Potentiometric and conductometric studies of complexes of some transition metals with 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one

1999 ◽  
Vol 77 (7) ◽  
pp. 1305-1309 ◽  
Author(s):  
Ashraf A El-Bindary ◽  
Adel Z El-Sonbati ◽  
Hanan M Kera
Keyword(s):  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Water Mixture ◽  
Dissociation Process ◽  
Different Temperatures ◽  
The Stability ◽  
Dissociation And Stability Constants ◽  
Key Words 4

Proton-ligand dissociation constants of 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one (AHMP) and metal-ligand stability constants of its complexes with some transition metal ions were calculated potentiometrically in 0.1 M KCl and 50% (v/v) ethanol-water mixture. The order of stability constants was found to be Th4+ > UO22+ > Ce3+ > La3+ > Mn2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The dissociation constant, pK1H, of AHMP and the stability constants, log K, of their complexes were determined at different temperatures (298, 308, and 318 K). The corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, exothermic, or endothermic (depending the metal), and entropically favourable. The stoichiometries of these complexes were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. Key words: 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one, dissociation and stability constants, thermodynamic parameters, stoichiometries.

Potentiometric and thermodynamic studies of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)-sulfamoyl]phenylazo}-2-pyrazolin-5-one and its metal complexes

2006 ◽  
Vol 60 (1) ◽  
Author(s):  
A. Fouda ◽  
A. Al-Sarawy ◽  
E. El-Katori
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Stability Constants ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Effect Of Temperature ◽  
Water Mixture ◽  
Dissociation Process ◽  
The Stability ◽  
Metal Ligand

AbstractThe dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Cu2+, La3+, Hf3+, UO22+, Zr4+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable.

scholarly journals Potentiometric and spectrophotometric studies of the complexation of Schiff-base hydrazones containing the pyrimidine moiety

2003 ◽  
Vol 68 (10) ◽  
pp. 729-749 ◽  
Author(s):  
H.S. Seleem ◽  
B.A. El-Shetary ◽  
S.M.E. Khalil ◽  
M. Shebl
Keyword(s):  
Schiff Base ◽  
Ionic Strength ◽  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Elemental Analysis ◽  
Mass Spectra ◽  
Dissociation Constants ◽  
The Stability ◽  
Pyrimidine Moiety ◽  
Metal Ligand

Three Schiff-base hydrazones (ONN ? donors) were prepared by condensation of 2-amino-4-hydrazino-6-methylpyrimidine with 2-hydroxyacetophenone 2-methoxybenzaldehyde and diacetyl to yield 2-OHAHP, 2-OMeBHPand DHP respectively. The structures of these ligands were elucidated by elemental analysis, UV, IR, 1H-NMR and mass spectra. The metal?ligand stability constants of Mn2+, Fe3+,Co2+,Ni2+,Cu2+, Zn2+,Cd2+,UO22+ and Th4+ chelates were determined potentiometrically in two different media (75%(v/v) dioxane?water and ethanol?water) at 283, 293, 303 and 313 K at an ionic strength of 0.05 M (KNO3). The thermodynamic parameters of the 1:1 and 1:2 complexes were evaluated and are discussed. The dissociation constants of 2-OHAHP, 2-OMeBHP and DHPligands and the stability constants of Co2+, Ni2 and Cu2+ with 2-OHAHP were determined spectrophotometrically in 75 % (v/v) dioxane?water.

scholarly journals The Stability Constants and Thermodynamic Parameters of Borate - Carbohydrate Complexes by pH Measurements

2012 ◽  
Vol 25 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Farida Akhtar ◽  
Md Anisur Rahman ◽  
DM Shafiqul Islam ◽  
Md Anamul Hoque
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Chemical Society ◽  
Ph Measurements ◽  
Negative Contribution ◽  
Exothermic Process ◽  
Different Temperatures ◽  
The Stability

The complexation of borate with carbohydrates was studied potentiometrically at  temperatures 298.15-328.15K in aqueous medium at constant ionic strength, I = 0.1M  KCl. The stability constants (?) and thermodynamic parameters of borate-carbohydrate  complexes were determined using the technique proposed by Verchere and Hlaibi.  Carbohydrates such as D-fructose, D-Sorbitol, D-Mannitol, D-Galactose, D-Glucose and  D-Raffinose were used as ligands in this study. The ?1 values for the complexes at  different temperatures were found to follow the order: D-fructose > D-Sorbitol > DMannitol > D-Galactose > D-Glucose > D-Raffinose. The ?G0 values were found to be  negative and the negative values increased according to the above order. The values of  ?H0 and ?S0 were both negative which indicated that the complex formation was an  exothermic process and the spontaneity of its formation is driven by enthalpic  contribution overcoming the negative contribution of ?S0. DOI: http://dx.doi.org/10.3329/jbcs.v25i1.11766 Journal of Bangladesh Chemical Society, Vol. 25(1), 15-20, 2012

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

2012 ◽  
Vol 239-240 ◽  
pp. 1573-1576
Author(s):  
Zhu Qing Gao ◽  
Xiao Dong Cai ◽  
Kai Cheng Ling
Keyword(s):  
Stability Constants ◽  
Tannic Acid ◽  
Ph Value ◽  
Protonation Constants ◽  
Conditional Stability ◽  
Tannin Extract ◽  
Acid Effect ◽  
Different Temperatures ◽  
The Stability ◽  
Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

Physicochemical investigation on thiomalate complexes of nickel

1968 ◽  
Vol 21 (3) ◽  
pp. 641 ◽  
Author(s):  
RS Saxena ◽  
KC Gupta ◽  
ML Mittal
Keyword(s):  
Aqueous Medium ◽  
Stability Constants ◽  
Alternative Methods ◽  
Acid System ◽  
Kcal Mole ◽  
Physicochemical Investigation ◽  
Different Temperatures ◽  
The Stability ◽  
Ph Range ◽  
Deep Violet

Potentiometric and conductometric studies of the nickel-thiomalic acid system, in aqueous medium of 0. lM KNO3, reveal the formation of two complexes; one light violet 1 : 1 predominating at pH 6.5-7.5 and another deep violet 1 : 2 in the pH range 8.5-10.0. The stability constants of the complexes formed have been determined by applying Calvin and Melchior's extension of Bjerrum's method at three different temperatures and were further refined by using alternative methods. The logK values (final) for 1 : 1 and 1 : 2 complexes at 20, 25, and 30� have been found to be 7.86, 7.87, 7.96, and 6.24, 6.31, 6.39 respectively. The values of the overall changes in ΔG, ΔH, and ΔS accompanying the reaction have also been evaluated at 25� and found to be -19.31 kcal/mole, -8.77 kcal/mole, and +35.36 cal/deg respectively.

scholarly journals Exchange of Some Divalent Metal Cations and Their Effect on the Dissociation of Iron(III) Phosphate

1996 ◽  
Vol 13 (4) ◽  
pp. 241-260 ◽  
Author(s):  
S. Mustafa ◽  
A. Naeem ◽  
N. Rehana ◽  
T. Hussain
Keyword(s):  
Transition Metal ◽  
Thermodynamic Parameters ◽  
Alkaline Earth ◽  
Dissociation Constants ◽  
Ph Value ◽  
Transition Metal Ions ◽  
Divalent Metal ◽  
Solution Ph ◽  
Divalent Metal Cations ◽  
Titration Data

Potentiometric titrations of iron(III) phosphate have shown an apparently weak monobasic acid behaviour towards alkali, alkaline earth and divalent transition metal ions. The selectivity sequence and dissociation of the exchanger was found to increase in the order Cu2+ > Zn2+ > Ni2+ > Ca2+ > K+. The dissociation constants of iron(III) phosphate have been determined from Potentiometric titration data in the temperature range 303–323 K. In addition, the exchange of Cu2+, Zn2+ and Co2+ on iron(III) phosphate and the effect of these ions on dissociation were also studied as a function of concentration, temperature and solution pH value. The thermodynamic parameters ΔH0, ΔS0 and ΔG0 for the dissociation of iron(III) phosphate are also presented.

Substituierte 2-Chloracetessigsäureanilide und ihre Metallchelate / Substituted 2-chloroacetoacetanilides and their metal chelates

1970 ◽  
Vol 25 (12) ◽  
pp. 1386-1388 ◽  
Author(s):  
A. Kettrup ◽  
J. Abshagen
Keyword(s):  
Stability Constants ◽  
Chelating Agents ◽  
Dissociation Constants ◽  
Metal Chelates ◽  
Ph Measurements ◽  
The Stability ◽  
Copper Chelates

The preparation of 2-chloroacetoacetanilides and the preparation of their metal chelates is described.The dissociation constants of the chelating agents and the stability constants of the copper chelates were determined by potentiometric pH-measurements

Chelating Tendencies of Some N-(2-Acetyl-1,3-Indandione) Trialkyl Ammonium Iodides with Transition Metal Ions

1973 ◽  
Vol 28 (5-6) ◽  
pp. 317-318 ◽  
Author(s):  
M. K. Bachlaus ◽  
K. L. Menaria ◽  
P. Nath
Keyword(s):  
Free Energy ◽  
Complex Formation ◽  
Transition Metal ◽  
Copper Complex ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Iron Complex ◽  
Potentiometric Studies ◽  
Kcal Mole ◽  
The Stability

The ligands T.P.A.I.* and T.B.A.I.** have been synthesised and their dissociation constants are 1.738 · 10-10 and 1.412 · 10-8 respectively. The potentiometric studies show that these reagents form 1 : 1 complex with copper(II) and iron(II). The stability constants of copper complex and iron complex with T.P.A.I. are 6.43 and 6.51 respectively and for T.B.A.I. 4.36 and 4.24 respectively. The free energy of complex formation at 25°C are 8.76 Kcal/mole and 8.87 Kcal/mole for Cu (II)-T.P.A.I. and Fe (II)-T.P.A.I. respectively, whereas the free energy of the Cu (II)-T.B.A.I. and Fe(II)-T.B.A.I. are 5.94 Kcal/mole and 5.78 Kcal/mole respectively.

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