From neutral to ionic species: amine–p-tert-butylcalix(n)arene (n= 6, 8) interaction. Electrochemical, thermodynamic and structural studies in benzonitrile
- 1 January 1993
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 89 (15) , 2727-2736
- https://doi.org/10.1039/ft9938902727
Abstract
Solubilities and derived Gibbs energies, enthalpies and entropies of solution of p-tert-butylcalix(n)arenes (n= 4, 6, 8) in benzonitrile at 298.15 K are reported. An important consequence of amine–calixarene interactions in solution is the generation of new electrolytes. Thus, using two different calixarenes (cyclic hexamer and octamer) and various amines, conductance measurements are performed in order to derive equilibria data for the process involving two neutral species to give an electrolyte, as a result of a proton-transfer reaction from the calixarene to the amine. The results obtained by conductivity are checked by using a combination of pKa values for p-tert-butylcalix(n)arene and various amines in benzonitrile calculated from potentiometric data. Thermodynamic parameters for these processes obtained from titration calorimetry reflect the distinctive properties of cryptands relative to other cyclic and aliphatic amines, suggesting that cryptand 222 is likely to host the proton released by the cyclic octamer in its cavity. 13C NMR studies on these systems revealed that the charge on the calixarene anion is delocalised as a result of a dynamic interchange of the remaining protons among the oxygen atoms present in the oligomeric molecule. Finally, the extraction of amines from aqueous solutions by calixarenes is analysed by taking into account the individual parameters that contribute to the overall process. It is shown that the transfer of amines from water to benzonitrile is favoured in the presence of calixarenes. Although the main contribution to the extraction process results from ion-pair formation in solution, the selective extraction of these amines by calixarenes is largely controlled by the transfer Gibbs energy of the amine from water to the non-aqueous phase.Keywords
This publication has 35 references indexed in Scilit:
- Thermodynamics of supramolecular systems: Recent developmentsPublished by Walter de Gruyter GmbH ,1993
- Triple-ion formation and acid–base strength of ions in protophobic aprotic solventsJournal of the Chemical Society, Faraday Transactions, 1992
- First report on electrochemical, thermodynamic and structural aspects of the interaction of p-tert-butylcalix[8]arene and cryptands in benzonitrileJournal of the Chemical Society, Chemical Communications, 1992
- Solution studies of haptens containing azobenzoate and substituted azobenzoate anions in water and in methanolJournal of the Chemical Society, Faraday Transactions, 1990
- Supramolecular chemistry ? Scope and perspectives: Molecules ? Supermolecules ? Molecular devicesJournal of inclusion phenomena and molecular recognition in chemistry, 1988
- Calixarenes. 20. The interaction of calixarenes and aminesJournal of the American Chemical Society, 1987
- Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. I. Polyazapolyoxa macrotricycle cylindrique et monocycle constitutifHelvetica Chimica Acta, 1985
- Heat capacities and volumes of the monoprotonation and diprotonation of cryptand 222 in water at 298.15 KThe Journal of Physical Chemistry, 1984
- Kinetics and mechanisms of formation of the di-endo protonated cryptand (2,1,1)H2 2+ including trapping and X-ray structure determination as its diperchlorate saltJournal of the Chemical Society, Chemical Communications, 1982
- Calculations on ionic solvation—V The calculation of partition coefficients of ionsJournal of Inorganic and Nuclear Chemistry, 1981