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Paths for the formation of dioxin-type xenobiotics: Quantum-chemical treatment 1. Formation of polychlorobiphenylenes from polychlorobenzenes
Authors:A. V. Fokin  Yu. A. Borisov  A. F. Kolomiets  N. I. Raevskii  V. G. Enchev  E. B. Bogachuk
Abstract:
The heats of formation of polychloroarynes (PCA's) from polychlorobenzenes (PCB's) have been calculated by the AMI method as a function of the composition and structure of the PCB's according to a two-step scheme including deprotonation with the formation of carbanions (PCCA's, DeltaH1) and dechlorination to PCA's (DeltaH2). The influence of the solvent on DeltaH1 and DeltaH2 has been evaluated in the framework of the solvaton model. It has been shown that the value of DeltaH1 decreases as the number of C1 atoms in the PCB is increased, while DeltaH2 increases along the same series due to the increase in the relative stability of the PCCA as the number of C1 atoms is increased. Although the dimerization of PCA's with the formation of polychlorobiphenylenes (PCBP's) is forbidden by orbital symmetry rules, calculations of fragments of the potential-energy surface have shown that this reaction takes place with an energy barrier amounting to about 1 kcal/mole.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Institute of Organic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 350–355, February, 1992.
Keywords:polychlorobenzenes  polychloroarynes  polychlorobiphenylenes  quantum-chemical calculations
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