Modeling and predicting pKa values of mono-hydroxylated polychlorinated biphenyls (HO-PCBs) and polybrominated diphenyl ethers (HO-PBDEs) by local molecular descriptors. (November 2015)

• Record Type: Journal Article
• Authors: Yu, Haiying; Wondrousch, Dominik; Yuan, Quan; Lin, Hongjun; Chen, Jianrong; Hong, Huachang; Schüürmann, Gerrit
• Is Part Of: Chemosphere. Volume 138(2015)
• Page Start: 829
• Page End: 836
• Publication Date: 2015-11
• Subjects: Hydroxylated polychlorinated biphenyls -- Hydroxylated polybrominated diphenyl ethers -- Dissociation constant -- pKa -- HF/6-31G∗∗ -- Local molecular parameters; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.08.012
• Languages: English
• ISSNs: 0045-6535

Abstract

Graphical abstract: Highlights: A predictive model for p K a of HO-PCBs and HO-PBDEs is developed. The model using local molecular descriptors has good predictive power. The energy and electronic characteristics that affect dissociation is analyzed. p K a values for 837 respective HO-PCBs and HO-PBDEs have been calculated. Abstract: Hydroxylated polychlorinated biphenyls (HO-PCBs) and polybrominated diphenyl ethers (HO-PBDEs) are attracting considerable concerns because of their multiple endocrine-disrupting effects and wide existence in environment and organisms. The hydroxyl groups enable these chemicals to be ionizable, and dissociation constant, p K a, becomes an important parameter for investigating their environmental behavior and biological activities. In this study, a new p K a prediction model was developed using local molecular descriptors. The dataset contains 21 experimental p K a values of HO-PCBs and HO-PBDEs. The optimized geometries by ab initio HF/6-31G ∗∗ algorithm were used to calculate the site-specific molecular readiness to accept or donate electron charges. The developed model obtained good statistical performance, which significantly outperformed commercial software ACD and SPARC. Mechanism analysis indicates that p K a values increase with the charge-limited donor energy EQ occ on hydroxyl oxygen atom and decrease with the energy-limited acceptor charge QE vac on hydroxyl hydrogen atom. The regression model was also applied to calculate p K a values for all 837 mono-hydroxylated PCBs and PBDEs in each class, aiming to provide basic data for the ecological risk assessment of these chemicals.