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Water soluble calix[4]arenes. A thermodynamic investigation of proton complex formation |
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| Authors: | Giuseppe Arena Rosario Cali Gaetano Giuseppe Lombardo Enrico Rizzarelli Domenico Sciotto Rocco Ungaro |
| Institution: | 1. Dipartimento di Scienze Chimiche , Universitá di Catania , Viale A. Doria 8, 95125 , Catania , Italy;2. Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico , C.N.R., Catania , Italy;3. Dipartimento di Scienze Chimiche , Universitá di Catania , Viale A. Doria 8, 95125 , Catania , Italy;4. Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico , C.N.R., Catania , Italy;5. Istituto di Chimica Organica, Universitá di Parma , Viale delle Scienze, Parma , Italy |
| Abstract: | Abstract Thermodynamic parameters of protonation of calix4]arene-p-tetra sulphonate were potentiometrically and calorimetrically determined in aqueous solution at 25 °C and I = 0.1 mol dm?3 (NaNO3). These values were compared with literature findings. ΔH° and ΔS° values reveal that the penta-anion protonation is energetically costly. In this connection the role played by hydrogen bonding and the cone conformation stabilization are critically discussed. Proton formation constants of the calix4]arene-p-tetrasulphonate-tetra-carboxylate derivative in the cone conformation were also potentiometrically determined under the same experimental conditions. |
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