Dioxaspiro-type structures as intermediates in the formation of polychlorinated dibenzo-p-dioxins. A semi-empirical AM1 molecular orbital study

The formation of polychlorinated dibenzo-p-dioxins (PCDDs) from the condensation of chlorophenols has been studied computationally employing the semi-empirical AM I methodology. Some possible reaction pathways, which include dioxaspiro-type structure as an intermediate, have been explored using the transition state (TS) theory. The electronic and structural properties of these intermediates are discussed. The results indicate that the calculated energetics are reasonable and the proposed reaction mechanisms, leading to the stable tricyclic ring structure of PCDDs, are thus feasible.