Photocyclization of Stilbenes and Related Molecules

1. In the rat chlorodiphenyl ethers are metabolized via two routes. The predominant reaction is aromatic hydroxylation; scission of the ether bond is a minor metabolic process.2. In all cases, primary hydroxylation takes place ortho and meta to the ether bond. Ortho-hydroxylation leads to the formation of 'predioxins' in cases where the parent compounds contain a chlorine atom in one of the ortho positions in the second ring.3. 5-Chloro-2-(2,4-dichlorophenoxy)phenol (Irgasan DP 300), a compound that meets the structural requirements of a predioxin, did not yield chlorodibenzo-p-dioxins or hydroxylated derivatives thereof.4. Irgasan DP 300 is excreted unchanged in faeces and urine (partly conjugated) but is also hydroxylated to five different monohydroxy metabolites which were found in urine; three of these were also present in faeces. As a result of scission of the ether bond 2,4-dichlorophenol occurred in urine and faeces, and 4-chlorocatechol in urine.5. Neither in the case of Irgasan DP 300, nor in tha...

Metabolism of Chlorodiphenyl Ethers and Irgasan® DP 300

Halogenated diphenyl ethers identified in avian tissues and eggs by GC/MS

Polychlorinated dibenzofurans (PCDFs) are thermally formed from polychlorinated biphenyls (PCBs) via general reaction routes. The pyrolysis of 3H and 14C labelled phenol and o‐ and p‐cresols at 665°‐865°C indicates that the mechanism of the thermal production of dibenzofuran is temperature dependent. The thermolysis of chlorinated phenols, ‐phenoxyacetic acids, and their salts and ‐phenoxy‐2‐phenols yield polychlorinated dibenzo‐p‐dioxins (PCDDs). On thermodegradation of polychlorinated diphenyl ethers, ester of 2,4,5‐T and chlorinated benzenes, a mixture of PCDFs and PCDDs is obtained. 1,2‐Ketocarbene species are involved in the thermal formation of dibenzo‐p‐dioxin from the salt of o‐halophenol.

Åe Norström

Papers

Studies on the formation of chlorodibenzofurans by irradiation or pyrolysis of chlorinated diphenyl ethers