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

Farid I El-Dossoki

doi:10.1155/2016/7234320

Abstract

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 ofT= (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, andNH3+). 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 (km) were determined. From the solubility data, the activity coefficients were obtained. The values of the total solubilities (ST) for naphthalen-1-ol and naphthalene-1,5-diol were found equal to the values of their neutral species (S0). 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.

Highlights

Naphthols are used in the manufacturing of dyes and other important compounds and as a ligand in the transition-metal catalysts [1, 2]
The maximum nA values measured in case of the ligands in the selected conditions has been found to be ∼0.9 for naphthalen-1-ol, ∼1.9 for naphthalene-1,5-diol, and 2.85 for 4-amino-3-hydroxynaphthalene-1-sulphonic acid revealing that the 1-naphthol has one ionisable hydrogen atom and 1,5 dihydroxynaphthalene molecule has two ionisable mKCl 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K
The acid-base properties and the solubilities of naphthalen1-ol, naphthalene-1,5-diol, and 4-amino-3-hydroxynaphthalene-1-sulphonic acid were determined 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

Summary

Introduction

Naphthols are used in the manufacturing of dyes (where they are classified as fast dyes, with characteristic colors, and usually slightly cheaper than vat dyeing) and other important compounds and as a ligand in the transition-metal catalysts [1, 2]. Naphthols can be used in many organic syntheses [3, 4]. It was found that naphthol is used to decrease testosterone levels in adult men [5, 6] and to stain collagen in histology [7]. It is used for polychrome stains with animal tissue. For industry purposes naphthol is used for staining wool, nylon, paper, an oxidized aluminum, and soap [7]. Naphthols are pollutants as a result of their slow degradation

Objectives

Results

Conclusion