Conductance and Thermodynamic Study of the Complexation of Ammonium Ion with Different Crown Ethers in Binary Nonaqueous Solvents

Abstract

A conductance study of the interaction between ammonium ion and 18-Crown-6 (18C6), dicyclohexano-18-crown-6 (DC18C6), ditertbutyl-dicyclohexano-18-crown-6 (t-bu) 2 DC18C6, diaza-15-crown-5 (DA15C5), dibenzo-21-crown-7 (DB21C7) and N-Phenylaza-15-crown-5 (NPA15C5) in acetonitril-dimethylsulfoxide mixture was carried out at various temperatures. The formation constants of the resultant 1:1 complexes were determined from the molar conductance-mole ratio data and found to vary in the order of DA15C5 > DC18C6 > 18C6 > (t-bu) 2 DC18C6 > DB21C7 > NPA15C5.The enthalpy and entropy of the complexation reactions were determined from the temperature dependence of the formation constants.

Conductometric Studies of Thermodynamics of Complexation of Co2+, Ni2+, Cu2+, and Zn2+ Cations with Aza-18-crown-6 in Binary Acetonitrile-Methanol Mixtures

“…However, the observed increase (or decrease, depending on the nature of the metal ion) in ΔH • value upon addition of MeOH to the solvent mixture will be compensated by an increase (or decrease) in the corresponding ΔS • value. The existence of such a compensating effect ( Figure 6) between ΔH • and ΔS • values, which has been frequently reported for a variety of metal-ligand systems [ [23][24][25], would cause the overall change in the ΔG • value of the complex to be smaller than might be expected from the change in either ΔH • or ΔS • independently. There is an entropy-driven stabilization for Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ complexation in AN-MeOH mixtures.…”

Simultaneous separation and extraction of Ag(I), Pb(II) and Pd(II) ions by solid phase method and determination of these ions by flame atomic absorption spectrometry

“…], [L] and f represent the equilibrium molar concentration of complexes, free cation, free ligand and the activity coefficient of the species, respectively. Under the dilute conditions used, the activity coefficient of uncharged crown ether, f (L) can be reasonably assumed as unity [19][20][21][22][23][24]. The use of Deby-Huckel limiting law of 1:1 electrolytes [25], lead to the conclusion that f (M n? )…”

“…3 and 4 to the molar conductance-mole ratio data using a non linear leastsquares program KINFIT [27]. The details are described elsewhere [19][20][21][22]. General extraction procedure Extraction were performed using Empore TM membrane disks (3 M CO., St. paul, MN, USA): 47 mm diameter, 0.5 mm thickness with 90% octadecyl-bonded silica 18 lm particle size) and 10% PTFE fiber.…”

“…A dip-type conductivity cell made of platinum black, with the cell constant of 0.832 cm -1 was used. In all measurements the cell was thermostated at 25.0 ± 0.1°C by using a MLW thermostated-circular water bath as described elsewhere [19][20][21][22].…”

Thermodynamic analysis of alkali metal complex formation of polymer-bonded crown ether

“…The extraction can be monitored by UV/Vis spectroscopy 7,8 and enables thermodynamic analysis if suitable counterions are used. [9][10][11][12][13] Besides, the thermodynamics of complex formation of ionic compounds with crown ethers in various organic solvents [14][15][16] as well as in mixed non-aqueous solutions 17,18 has been explored. The stability of a formed complex depends on the diameter of the crown ether and the radius of the metal cation.…”