TRIIODO-5-NITROBENZENE

It was mentioned earlier (Sec. 8.6) that for iodo-de-diazoniation no catalyst is necessary because the redox potential of the iodide ion (E° = 1.3 V) is sufficient for an electron transfer to the arenediazonium ion. The reaction was actually observed by Griess (1864 c). Four iodo-de-diazoniation procedures are described in Organic Syntheses. For the syntheses of iodobenzene and 4-iodophenol (Lucas and Kennedy, 1943, and Daines and Eberly, 1943, respectively) KI is used in equimolar quantity and in 1.2 molar excess. However, for 2-bromoiodobenzene and for 1,3,4-triiodo-5-nitrobenzene (replacement of a diazonio group in the 4-position by iodine), up to... 

Diazonium salt solutions that have been obtained from weakly basic amines in concentrated H2S04 with nitrosylsulfuric acid and 85 % phosphoric acid give good yields of the derived aryl iodides when treated with cold aqueous KI for example, the preparation of 1,2,3-triiodo-5-nitrobenzene from 2,6-diiodo-4-nitroaniline is described in detail in Organic Syntheses 1223 and m-iodonitrobenzene, l,2-diiodo-4-nitrobenzene, l,4-diiodo-2-nitrobenzene, and 1,2,4-tri-iodo-3-nitrobenzene have been obtained analogously.1224... 

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