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Org. Synth. 1963, 43, 60
DOI: 10.15227/orgsyn.043.0060
IODOSOBENZENE
[Benzene, iodoso-]
Submitted by H. Saltzman and J. G. Sharefkin1.
Checked by Melvin S. Newman and Narinder Gill.
1. Procedure
Caution! This compound explodes if heated to 210°.
Finely ground iodosobenzene diacetate2 (32.2 g., 0.10 mole) is placed in a 250-ml. beaker, and 150 ml. of 3N sodium hydroxide is added over a 5-minute period with vigorous stirring. The lumps of solid that form are triturated with a stirring rod or spatula for 15 minutes, and the reaction mixture stands for an additional 45 minutes to complete the reaction. One hundred milliliters of water is added, the mixture is stirred vigorously, and the crude, solid iodosobenzene is collected on a Büchner funnel. The wet solid is returned to the beaker and triturated in 200 ml. of water. The solid is again collected on the Büchner funnel, washed there with 200 ml. of water, and dried by maintaining suction. Final purification is effected by triturating the dried solid in 75 ml. of chloroform in a beaker. The iodosobenzene is separated by filtration (Note 1) and air-dried; weight 18.7–20.5 g. (85–93%); m.p. 210° (Caution! Explodes!). Iodometric titration3 shows the product to be more than 99% pure (Note 2).
2. Notes
1. The filtrate yields unreacted diacetate on evaporation.
2. The purity of the iodosobenzene depends on the purity of the diacetate used.
3. Discussion
Iodosobenzene has been prepared by the action of sodium or potassium hydroxide solution on iodobenzene dichloride3,4 and by addition of water to the dichloride.5
4. Merits of the Preparation
This method of preparing iodosobenzene is preferable to older ones based on iodosobenzene dichloride because iodosobenzene diacetate2 is more stable and more conveniently prepared than the dichloride3 and the overall yield is greater (75% versus 54%).
The procedure seems to be a general way of preparing iodosoarenes with electron-donating substituents, for the submitters have used it to obtain good yields of o-, m- and p-iodosotoluene, 2- and 4-iodoso-m-xylene, 2-iodoso-p-xylene, o-iodosophenetole, and 4-iodosobiphenyl.
Iodosoarenes are useful in the preparation of iodonium salts, Ar2I+X.6
This preparation is referenced from:

References and Notes
  1. Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, New York.
  2. J. G. Sharefkin and H. Slatzman, this volume, p. 660.
  3. H. J. Lucas, E. R. Kennedy, and M. W. Formo, Org. Syntheses, Coll. Vol. 3, 483 (1955).
  4. C. Willgerodt, Ber., 25, 3494 (1892); 26, 357, 1802 (1893); P. Askenasy and V. Meyer, Ber., 26, 1354 (1893); C. Hartmann and V. Meyer, Ber., 27, 502 (1894).
  5. C. Willgerodt, Ber., 26, 357 (1893); G. Ortoleva, Chem. Zentr., 1900, 722.
  6. F. M. Beringer, R. A. Falk, M. Karniol, I. Lillien, G. Masullo, M. Mausner, and E. Sommer, J. Am. Chem. Soc., 81, 343 (1959) C. Hartmann and V. Meyer, Ber., 27, 426, 504 (1894).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

o-, m- and p-iodosotoluene

2- and 4-iodoso-m-xylene

sodium hydroxide (1310-73-2)

chloroform (67-66-3)

potassium hydroxide (1310-58-3)

sodium (13966-32-0)

iodobenzene dichloride (2401-21-0)

Iodosobenzene,
Benzene, iodoso- (536-80-1)

Iodosobenzene diacetate (3240-34-4)

iodosobenzene dichloride

4-iodosobiphenyl

2-iodoso-p-xylene

o-iodosophenetole