Study On The Solubility And Octanol/Water Partition Coefficients Of The Benzoic Acid Derivatives

Benzoic acid derivatives, which are largely produced and widely used, may have polluted the water environment to various degrees and are considered as important priority contaminants. In order to evaluate the environmental contamination performance of benzoic acid derivatives, basic physical-chemical data must be known.The aqueous solubility and 1-octanol/water partition coefficient(slgKow) are the two most important physical-chemical properties of organic substances, which are essential for understanding their environmental behavior and are the hotspot and emphases problem in the international environment.Using a laser monitoring observation technique, solubilities of benzoic acid derivatives in water or in 1-octanol as a function of temperature have been determined in this work. Also, using the shake flask method, the lgKow of these compounds has been investigated in this study.The laser monitoring observation technique was designed and established in this work, and the reliability of the equipment was validated. The solubility of the 10 kind of benzoic derivatives in water and in 1-octanol were determined separately during the temperature range of 20-50℃. The experiments show that all the solubility of the benzoic derivatives, whether in the water and in the 1-octanol, increase with temperature. Owing to the special molecular structure, there is a large difference between solubility of these chemicals. And the solubility of different benzoic acid derivatives in water as a function of temperature varies significantly.The experimental solubility data are regressed with the Wilson equation, T-Wilson equation, the NRTL equation and theλH equation. The solubility data couldn't describe adequately with the Wilson equation if respect to some certain solution system. The experimental results show that the T-Wilson equation and theλH equation give good agreement with all experimental data, and the average relatively error is less than 2.2%. However, the solubility data couldn't regress well with the NRTL equation.New group AC-COOH, which is correlative with benzoic compounds, is defined for UNIFAC model. Furthermore,the interaction parameter of UNIFAC model was emended by a temperature dependent function, so it is named as T-UNIFAC model. It is found that the correlation results of the experimental data by T-UNIFAC model are better than that of UNIFAC model. The interaction parameters corresponding to the new group were obtained by fitting the experimental data with UNIFAC model and T-UNIFAC model, which are the helpful complementarities for the use of UNIFAC model.The 1-octanol/water partition coefficients of the ten kind benzoic acid derivatives were determined, when the pH is at random value and the partition coefficient is named as lgKow'. With increasing the pH value, the lgKow'decreased markedly during the pH value 3-5.The new solubility estimate lgKow model was put forward in which the solubility in 1-octanol was firstly introduced. Using the new model, estimated precision of the 1-octanol/water partition coefficients (lgKow) was increased sharply.The fragment constant model was revised for lgKow calculation of the benzoic acid derivatives and the fragments value and the correction factors value are proposed also. The new calculate model is well enough to calculate lgKow of the benzoic acid derivatives, and the estimation value of lgKow is consistent with the experimental value of lgKow.