Predicting gaseous reaction rates of short chain chlorinated paraffins with ·OH: overcoming the difficulty in experimental determination

Environ Sci Technol. 2014 Dec 2;48(23):13808-16. doi: 10.1021/es504339r. Epub 2014 Nov 17.

Abstract

Short chain chlorinated paraffins (SCCPs) are under evaluation for inclusion in the Stockholm Convention on persistent organic pollutants. However, information on their reaction rate constants with gaseous ·OH (kOH) is unavailable, limiting the evaluation of their persistence in the atmosphere. Experimental determination of kOH is confined by the unavailability of authentic chemical standards for some SCCP congeners. In this study, we evaluated and selected density functional theory (DFT) methods to predict kOH of SCCPs, by comparing the experimental kOH values of six polychlorinated alkanes (PCAs) with those calculated by the different theoretical methods. We found that the M06-2X/6-311+G(3df,2pd)//B3LYP/6-311 +G(d,p) method is time-effective and can be used to predict kOH of PCAs. Moreover, based on the calculated kOH of nine SCCPs and available experimental kOH values of 22 PCAs with low carbon chain, a quantitative structure-activity relationship (QSAR) model was developed. The molecular structural characteristics determining the ·OH reaction rate were discussed. logkOH was found to negatively correlate with the percentage of chlorine substitutions (Cl%). The DFT calculation method and the QSAR model are important alternatives to the conventional experimental determination of kOH for SCCPs, and are prospective in predicting their persistence in the atmosphere.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants / chemistry*
  • Atmosphere / chemistry
  • Chlorine / chemistry
  • Hydrocarbons, Chlorinated / chemistry*
  • Hydroxyl Radical / chemistry
  • Paraffin / chemistry*
  • Prospective Studies
  • Quantitative Structure-Activity Relationship*

Substances

  • Air Pollutants
  • Hydrocarbons, Chlorinated
  • Hydroxyl Radical
  • Chlorine
  • Paraffin