Gibbs Transfer Energies of Macrocyclic Ligands in Methanol+N-methyl-2-pyrrolidinone Mixtures by Solubility and Partition Measurements

Abstract

The standard Gibbs transfer energies of 18-crown-6,dibenzo-18-crown-6, cryptands 21, 22 and 222 frommethanol to methanol + N-methyl-2-pyrrolidinone(NMP) mixtures were determined from solubility andpartition measurements at 30 °C. While the Gibbs energy of transfer of 18-C-6 is positive,increases up to X_NMP = 0.7 and thereafter decreases, the transfer energy ofdibenzo-18-C-6 is negative and decreases with the addition of NMP. However,the transfer energy of cryptand 21becomes increasingly negative with theaddition of NMP while that of cryptand 22 ispositive and increases under the sameconditions. For cryptand 222, the transferenergy is slightly negative up toX_NMP = 0.5 butdecreases markedly at higher compositions of NMP. These results have been explainedin terms of the various types of interaction between the ligand molecules, solventcomponents and the effect of solvent–solvent interactions on them.