Protonation and Solvation Thermodynamics of Some Naphthol Derivatives in KCl Aqueous Solution of Different Ionic Strengths

الملخص EN

The acid-base properties of naphthalen-1-ol (L1), naphthalene-1,5-diol (L2), and 4-amino-3-hydroxynaphthalene-1-sulphonic acid (L3) were characterized from pH-metric measurements in pure water and in different concentrations (0–4 mol kg−1) of aqueous KCl solutions at the temperature range of T = (293.15 to 213.15) K at 5 K intervals.

The results reveal that naphthalen-1-ol and naphthalene-1,5-diol molecules have two ionisable protons (of the hydroxyl groups) while 4-amino-3-hydroxynaphthalene-1-sulphonic acid has three ionisable protons (hydrogen ion of the hydroxyl group, SO3H, and N H 3 + ).

Modeling of the data was done by applying Debye-Hückel model.

The protonation and the solvation processes of all studied ligands are spontaneous and endothermic processes.

Also the solubilities of naphthalen-1-ol, naphthalene-1,5-diol, and 4-amino-3-hydroxynaphthalene-1-sulphonic acid were determined.

The data were analyzed using Setschenow equation and the values of Setschenow coefficients ( k m ) were determined.

From the solubility data, the activity coefficients were obtained.

The values of the total solubilities ( S T ) for naphthalen-1-ol and naphthalene-1,5-diol were found equal to the values of their neutral species ( S 0 ).

On the other hand, the total solubility for 4-amino-3-hydroxynaphthalene-1-sulphonic acid is different from that of its neutral species.

The results also indicate solubility decrease in pure water from L1-L2-L3.