Stability constants and thermodynamic behaviour of the complex formation of two crown ethers with zinc (II) and copper (II) ions in water + acetonitrile mixed solvent: a conductivity measurement study

Ultraviolet spectral studies of hydrogen bonding between phenol and N,N-dimethylacetamide (DMA) in several media are reported. The equilibrium constant for the formation of the phenol–DMA complex is strongly solvent dependent, varying from 295 1/mole in cyclohexane to 130 in CCl4 and 16 in CHCl3, all at 28°. The greatly reduced value in CHCl3 indicates that the measured equilibrium constant is only an apparent one which does not take into account the decrease in free DMA concentration resulting from hydrogen-bonded complex formation with the solvent acting as hydrogen donor. In CCl4/CHCl3 mixed solvent, in the range of [chloroform] = 0 to 1.227 M, the measured equilibrium constant, K′, varies linearly with K′ [chloroform]. The slope of the line corresponds to the equilibrium constant for the formation of the hydrogen-bonded complex between CHCl3 and DMA in CCl4. The value, 0.9 1/mole, agrees with that obtained from a proton magnetic resonance method. The agreement is particularly noteworthy when we consider that the concentrations of phenol used in the proton magnetic resonance and ultraviolet spectral methods differ by a factor of 200, which leads definitely to the conclusion that the hydrogen-bonded CHCl3–DMA complex formed is 1:1. In cyclohexane/CHCl3 mixed solvent, similar results are obtained.

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Equilibrium Studies of Alkyltin(IV) Complexes with D-Glucosamine

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19971023 ◽

1997 ◽

Vol 62 (7) ◽

pp. 1023-1028 ◽

Cited By ~ 2

Author(s):

Mohamed M. Shoukry ◽

Samir M. El-Medani

Keyword(s):

Complex Formation ◽

Stability Constants ◽

Acid Base ◽

Complex Formation Equilibria ◽

Equilibrium Studies ◽

Formation Equilibria ◽

Effects Of Temperature ◽

The Stability

The acid-base and complex-formation equilibria involving glucosamine and its complexes with alkyltin(IV) chlorides have been studied by potentiometric technique. The results prove to a formation of 1 : 1 complex with trialkyltin(IV) and both 1 : 1 and 1 : 2 complexes with dialkyltin(IV) species. The stability constants in water were determined, the effects of temperature (from 15 to 35 °C) and ethanol (up to 88 vol.%) was studied and the speciation of the complexes was resolved.

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The affinity of aldehydic compounds to complex formation. Nickel(II) and cobalt(II) complexes with 2-pyridinecarboxaldehyde

Canadian Journal of Chemistry ◽

10.1139/v77-362 ◽

1977 ◽

Vol 55 (14) ◽

pp. 2613-2619 ◽

Cited By ~ 3

Author(s):

M. S. El-Ezaby ◽

M. A. El-Dessouky ◽

N. M. Shuaib

Keyword(s):

Complex Formation ◽

Aqueous Solutions ◽

Stability Constants ◽

Metal Ion ◽

Experimental Conditions ◽

Complex Species ◽

Spectrophotometric Methods ◽

Complex Equilibria ◽

The Stability ◽

Hydroxy Groups

The interactions of Ni(II) and Co(II) with 2-pyridinecarboxaldehyde have been investigated in aqueous solutions at μ = 0.10 M (KNO3) at 30 °C. The stability constants of different complex equilibria have been determined using potentiometric methods. Spectrophotometric methods were also used in the case of the nickel(II) – 2-pyridinecarboxaldehyde system. It was concluded that nickel(II) and cobalt(II), analogous to copper(II), enhance hyrdation of 2-pyridinecarboxaldehyde prior to deprotonation of one of the geminal hydroxy groups. Complex species of 1:1 as well as 1:2 metal ion to ligand composition exist under the experimental conditions used.

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