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Carbon‐14‐labeled 2,3,7,8‐ and 1,2,7,8‐tetrachlorodibenzofuran
Author(s) -
Gray Allan P.,
McClellan W. J.,
Dipinto V. M.
Publication year - 1981
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580180408
Subject(s) - chemistry , homolysis , dibenzofuran , heterolysis , medicinal chemistry , yield (engineering) , ether , diphenyl ether , organic chemistry , catalysis , radical , materials science , metallurgy
Both 2,3,7,8‐ and 1,2,7,8‐ tetrachlorodibenzofuran ‐U 14 C, specific activity 57 mCi/mmol, have been obtained in low yield but at < 98% purity via Pschorr cyclization of o ‐phenoxyaniline ‐U 14 C, chlorination of the resultant dibenzofuran and separation of the tetrachloro isomers by hplc. The lower yields obtained in the Pschorr cyclization of “hot” o ‐phenoxyaniline in comparison with the “cold” material are postulated to result from enhanced homolytic relative to heterolytic cleavage of the “hot” diazonium ion leading to a “hot” free radical which polymerizes. The completely anomalous results observed in the attempted palladium acetate‐mediated cyclization of diphenyl ether‐ U 14 C are likewise interpreted in terms of the intervention of a “hot” free radical.