Photochemistry of Polyhaloarenes. 4. Phototransformations of Perchloro-o-phenoxyphenol in Basic Media

Article abstract of DOI:10.1021/jo00371a004

Irradiation of the sodium salt of the conjugate base of perchloro-o-phenoxyphenol (PreD^-Na⁺) in methanol (300 nm) in the presence of sensitizer m-methoxyacetophenone generates ether cleavage products and mono- and di-dechlorination with no cycliozation to OCDD.In the presence of sensitizer and excess triethylamine, irradiation of perchloro-o-phenoxyphenol leads to OCDD as a major product with ether cleavage and dechlorination products representing important reaction pathways.Photodecomposition of the conjugate base of perchloro-o-phenoxyphenol in methanol reveals a small amount of cyclization, while irradiation in methanol in the presence of a 10-fold excess of triethylamine increases the quantum yield for cyclization 17-fold.The photolytic transformations of the conjugate base of perchloro-o-phenoxyphenol in the presence of excess triethylamine are dependent upon solvent polarity with the quantum yield for cyclization increasing strongly in methanol or water/acetonitrile (70:30) relative to that in dibutyl ether.These results are interpreted in terms of electron transfer to PreD^- to form a radical dianion.