A novel model to predict gas–phase hydroxyl radical oxidation kinetics of polychlorinated compounds. (April 2017)

• Record Type: Journal Article
• Authors: Luo, Shuang; Wei, Zongsu; Spinney, Richard; Yang, Zhihui; Chai, Liyuan; Xiao, Ruiyang
• Is Part Of: Chemosphere. Volume 172(2017)
• Page Start: 333
• Page End: 340
• Publication Date: 2017-04
• Subjects: Polychlorinated compounds -- Second–order rate constants -- Polarizability -- Hammett constant -- Meta–substituents -- QSAR; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2017.01.014
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this study, a novel model based on aromatic meta–substituent grouping was presented to predict the second–order rate constants ( k ) for OH oxidation of PCBs in gas–phase. Since the oxidation kinetics are dependent on the chlorination degree and position, we hypothesized that it may be more accurate for k value prediction if we group PCB congeners based on substitution positions ( i.e., ortho ( o ), meta ( m ), and para ( p )). To test this hypothesis, we examined the correlation of polarizability ( α ), a quantum chemical based descriptor for k values, with an empirical Hammett constant ( σ + ) on each substitution position. Our result shows that α is highly linearly correlated to ∑ σ o, m, p + based on aromatic meta–substituents leading to the grouping based predictive model. With the new model, the calculated k values exhibited an excellent agreement with experimental measurements, and greater predictive power than the quantum chemical based quantitative structure activity relationship (QSAR) model. Further, the relationship of α and ∑ σ o, m, p + for PCDDs congeners, together with highest occupied molecular orbital (HOMO) distribution, were used to validate the aromatic meta–substituent grouping method. This newly developed model features a combination of good predictability of quantum chemical based QSAR model and simplicity of Hammett relationship, showing a great potential for fast and computational tractable prediction of k values for gas–phase OH oxidation of polychlorinated compounds. Graphical abstract: Highlights: A novel aromatic meta–substituent grouping model for k of OH oxidation of PCBs. Polarizability is highly correlated to Hammett constant based on meta–substituents. This model features a combination of good predictability and simplicity.