Effects of pH on the water solubility and 1-octanol–water partition coefficient of 2,4,6-tribromophenol

Abstract

2,4,6-Tribromophenol (TBP) is expected to exist in both ionic and non-ionic forms in the environment due to ionisation of the phenolic group at near neutral pH. In this study, the water solubility (S_w) and 1-octanol–water partition coefficient (K_ow) of aqueous solutions of TBP at various pH values were measured using the shake flask method. The ionisation resulted in increasing S_w and decreasing K_ow by two to three orders of magnitude. From the experimental results, the environmental partitioning characteristics of TBP and the effect of pH on partitioning were discussed through a comparison with the properties of tetrabromobisphenol A (TBBP-A), which has two phenolic groups. Furthermore, the pH dependence of S_w and K_ow was represented using a Henderson–Hasselbalch type model and the validity of the model was evaluated. The model was found to be highly useful for predicting the pH dependence within the range of pH 3 to 9.