An evaluation of the heat of formation of chlorinated dioxins and its application to isomer abundance predictions

Heats of formation for dibenzo-p-dioxin and all chlorinated dioxins are derived and combined with standard entropies and heat capacities to obtain a computational database for prediction for these compounds. Databases based on a published preditive method for dioxins, and on general group additivity data have also been constructed. The predicted relative abundances of the isomers for all degrees of chlorination from the three databases are compared. The abundances of the tetra- to heptachlorodioxin isomers are compared with those predicted by Unsworth using MOPAC, and with experimentally determined concentrations from combustion systems.