AQUAFAC: Application to the estimation of aqueous solubility and Henry`s law constant
- Univ. of Arizona, Tucson, AZ (United States). Dept. of Pharmaceutical Sciences
The aqueous activity coefficient of an organic compound has a direct bearing on aqueous solubility as well as air/water partitioning (Henry`s law constant). AQUAFAC, Aqueous Functional group Activity Coefficients, is aimed at the development of a totally new set of group contribution values for estimating the aqueous activity coefficients of organic compounds. The present study derives 50 new group values (q-values). These group values are based over 1000 compounds representing nearly 2,000 solubilities. Ten fold cross validation of the AGUAFAC model gives an average root mean square error of 0.45 log units. Aqueous solubilities are estimated from AQUAFAC by log S{sub spred} = {minus}({Delta}S{sub m}/5706)(MP{minus}25){minus}{Sigma}n{sub i}q{sub i} where, S{sub pred} = predicted solubility (Molar), {Delta}S{sub m} = entropy of melting (joule/deg mole), MP = melting point ({degree}C), n{sub i} = number of times group i appears, q{sub i} = contribution of group i to the total activity coefficient. Solubilities for a diverse set of environmentally relevant compounds have been successfully estimated using the above approach. Preliminary results have found the AQUAFAC method to be more accurate in estimating aqueous solubilities than a standard method which uses octanol/water partition coefficient information. In addition, AQUAFAC can be combined with a simple new method for estimating vapor pressure, enabling a new method for estimating Henry`s law constants.
- OSTI ID:
- 40014
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
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