Chemistry is the science of change. But why do chemical reactions take place? Why do chemicals react with each other? The answer is in thermodynamics and kinetics.In a document type is Article, the author is D’Aprano, Alessandro and a compound is mentioned, 33100-27-5, 1,4,7,10,13-Pentaoxacyclopentadecane, introducing its new discovery. 33100-27-5
Solvent Effects on Complexation of Crown Ethers with LiClO4, NaClO4 and KClO4 in Methanol and Acetonitrile
The thermodynamic formation constants Kf for complexation of Li+, Na+ and K+ with the crown ethers 12C4 and 15C5 have been determined in methanol and acetonitrile at 25 deg C using precision conductivity data.The method permits evaluation of very small Kf values (e.g., Kf = 6.98 mol-1-dm3 for LiClO4 + 12C4 in methanol) as well as fairly large values (e.g., Kf 0 2.73*104 mol-1-dm3 for NaClO4 + 15C5 in acetonitrile).The determination fo Kf values from condcutivity data takes into consideration the often neglected ion pair formation of both the uncomplexed and the complexed cations.Our results for Kf are generally consistent with previously reported values based on potentiometry, calorimetry, and polarography, but there are significant differences in several cases which we attribure to neglect of ion association both for uncomplexed or “free” cation Ka and the macrocyclic complexed cation Ka2.Our results are also consistent with the well known concept relating the magnitude of Kf to both the cavity diameter and ion-solvent interactions.Limiting molar conductivities Lambda2 for the complex salt (M-crown ether) (ClO4) in both solvents were generally found to be smaller or very close to the corresponding quantity Lambda1 for the binary MClO4-solvent system.However, in methanol, single ion limiting molar conductivities for the cationic complexes lambda2 exhibit anomalous behavior which is attributed to solvation differences between “free” cations and complexed cations. – Key words: Electrolytic, molar and ionic conductance; ion pair and complex ion formation; 12-crown-4; 15-crown-5; lithium, sodium and potassium perchlorate; acetonitrile; methanol; solvation effects; ion solvation; Gibbs energies of transfer.
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Reference£º
Chiral Catalysts,
Chiral catalysts – SlideShare