THERMODYNAMIC AND ELECTROCHEMICAL ASPECTS OF P-TERT-BUTYLCALIX[N]ARENES (N=4, 6, 8) AND THEIR INTERACTIONS WITH AMINES

Attention is drawn to the need of detailed thermodynamics in calixaren e chemistry. The reasons for increasing efforts in this area are under lined and suggestions for new issues to be addressed are given. The so lution thermodynamics of p-tert-butylcalix[n]arenes (n = 4, 6, 8) is d iscussed with particular reference to transfer Gibbs energies which re flect the selective solvation that the tetramer and the octamer underg o in the various solvents. This is followed by recent solution studies on amine-p-tert-butylcalix[n] arene (n = 4, 6, 8) in nitrobenzene and in benzonitrile at 298.15 K which indicate the lower acidic character of the tetramer relative to the hexamer and the octamer in these solv ents. As an implication of these results, very low conductivities are observed in studies involving the interaction of the former with amine s. Thus, thermodynamic studies suggest that p-tert-butylcalix[4]arene interacts with triethylamine in benzonitrile and in nitrobenzene throu gh hydrogen bonding or ion-pair formation. A thermodynamic cycle is us ed to investigate the effect associated with the interaction of the am ine with the tetramer in these solvents.