LIGHT AND DARK REACTIONS OF ORTHO-HALOIODOBENZENES WITH DIETHYL PHOSPHITE ION

o-Haloiodobenzenes react with diethyl phosphite ion in the dark in a manner wholly different from their reactions under irradiation. The photostimulated reactions afford o-phenylenebisphosphonic esters, except that ofluoroiodobenzene (If) undergoes replacement of iodine only, and are believed to occur by the SRN1 radical chain mechanism. The dark reactions afford respectively fluoro- and chlorobenzene, as well as iodide ion, from If and o-chloroiodobenzene (lc). The probable mechanism is nucleophilic attack on iodine to displace an o-halophenyl anion which then takes a proton from the solvent. Some of the products from o-bromoiodobenzene (lb) and o-diiodobenzene (li) appear to derive from benzyne arising from the o-halophenyl anions by halide ion loss. A minor product from lb or li, diethyl o-iodophenylphosphonate, appears to have its genesis in a novel ionic chain mechanism. © 1979, American Chemical Society. All rights reserved.