Formation constants of ternary complexes of copper(II), L/D-histidine and, in turn, glycine, L-alanine, L-valine, L-leucine, L-tryptophan, or L-phenylalanine have been determined potentio-metrically at 25 °C and I= 0.1 mol dm–3(KNO3). In the case of amino acids with aromatic side chains the ternary complexes containing ligands of opposite chirality are more stable than those having ligands of the same chirality; the opposite is true for amino acids with aliphatic residues. Calorimetric measurements have been carried out to obtain the enthalpy and entropy values associated with complex formation. Copper(II)–histamine ternary systems with L-alanine or L-phenylalanine have also been investigated. Comparison of the thermodynamic parameters pertinent to formation of the histamine complexes with those of the analogous histidine complexes allows one to ascertain the number of donor atoms involved in the co-ordination to copper(II), in the histidine systems. The determination of H and S values renders easier understanding of the factors determining Stereoselectivity in the above systems. The Stereoselectivity may be explained in terms of non-covalent interactions between side-chain residues. The role played by the histidine carboxylate in the molecular recognition of amino acids is also discussed

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The adsorption of butane-1,4-diol on a polarized Hg electrode from both NaF and Na2S04 solutions has been studied by means of electrocapillary and capacity curves. Analysis has been carried out both at constant charge and at constant potential. Irrespective of the choice of the electrical variable, adsorption has been found to conform to congruent Langmuir isotherms on the negative side of the adsorption maximum, and to non-congruent isotherms on the other side. Results suggest that molecules adsorb flat on the surface. Non congruence may be described in terms of a saturation coverage linearly decreasing with electric field. The inner layer capacity at constant amount adsorbed has been determined up to saturation coverage over a wide range of electric field. Results are discussed in terms of a polarization-dependent adsorbate-solvent interaction on the surface. A detailed molecular model of the adsorption layer is suggested.

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