Iodoxy compounds iodides

The iodoso- and, in particular, the iodoxy-compounds decompose with a puff when heated, since the oxygen which they contain is present in a state of tension. They liberate an equivalent amount of iodine from acidified potassium iodide solution and are thereby reconverted into iodobenzene. 

Iodobenzene [591-50-4], C6HBI, mol wt 204.02, 62.23% I, mp —30°C, bp 188—189°C, is a colodess liquid that rapidly becomes yellow and has a characteristic odor. It is insoluble in water, but completely miscible with alcohol, chloroform, and ether. It has a density of 1.832 g/mL at 20°C and a refractive index of 1.621 at 4°C. Iodobenzene is prepared by the reaction of iodine and benzene in the presence of an oxidizing agent and from benzeneiazonium sulfate and potassium iodide (122). Iodobenzene is used as a heavy liquid for refractive index determinations, but probably its principal use is in the synthesis of iodoso compounds, RIO iodoxy compounds, RI02 and iodonium salts, R IX. 

The following procedure is used in the analysis of iodoso and iodoxy compounds. In a 200-cc. iodine flask are placed 100 cc. of water, 10 cc. of 6 N sulfuric acid, 2 g. of iodate-free potassium iodide, 10 cc. of chloroform, and finally the sample, about 0.25 g. The flask is shaken for fifteen minutes (or longer, if the reaction is not complete), and then the mixture is titrated with 0.1 N sodium thiosulfate. If the sample is pure the change of color in the chloroform layer may be taken as the end point, but if impurities are present starch must be used, for the impurities impart a brownish color to the chloroform. This solvent is desirable, as it facilitates the reaction with potassium iodide by dissolving the reaction products. Iodosobenzene may be differentiated from iodoxybenzene, for the former reduces iodide ion in a saturated sodium borate solution, whereas the latter does not.1 The reactions involved are ... 

Iodoxy compounds and iodides from iodoso compounds... 

Oxidation of Allylic Iodides. m-CPBA oxidation of the primary allylic iodide (65) furnishes the secondary aUylic alcohol (66) (eq 26) this involves rearrangement of the iodoxy compound formed initially. 

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