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Organic Synthess - McKusick B.C.

McKusick B.C., Boekelheide V., Emmons W.D. Organic Synthess - New York, 1963. - 134 p.
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(Benzene, iodoso-)
CeH5I(OCOCH3)2 + 2NaOH -►
C6HeIO + 2NaOCOCH3 + H20
Submitted by H. Saltzman and J. G. Sharepkin.1
Checked by Melvin S. Newman and Narinder Gill.
1. Procedure
Caution! This compound explodes ij heated to 210°.
Finely ground iodosobenzene diacetate 2 (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 macerated 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 Buchner funnel. The wet solid is returned to the beaker and macerated in 200 ml. of water. The solid is again collected on the Buchner funnel, washed there with 200 ml. of water, and dried by maintaining suction. Final purification is effected by macerating 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!). Iodo-metric titration 3 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. Methods of Preparation
Iodosobenzene has been prepared by the action of sodium or potassium hydroxide solution on iodobenzenc dichloride M 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 diacetate 2 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 iodo-soarenes with electron-donating substituents, for the submitters have used it to obtain good yields of o-, m- and ^-iodosotoluene, 2- and 4-iodoso-m-xylene, 2-iodoso-/>-xylcne, o-iodosophenetole, and 4-iodosobiphenyl.
lodosoarenes are useful in the preparation of iodonium salts, Ar2I+X~.6
1 Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn 10, New York.
2 J. G. Sharefkin and H. Saltzman, this volume, p. 62.
s H. J. Lucas, E. R. Kennedy, and M. W. Formo, Org. Syntheses, Coll. Vol. 3, 483 (1955).
4 С. Willgerodt, Chem. Ber., 25, 3494 (1892); 26, 357, 1802 (1893); P. Askenasy and V. Meyer, Chem. Ber., 26,1354 (1893); С. Hartmann and V. Meyer, Chem. Ber., 27, 502 (1894).
s С. Willgerodt, Chem. 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); С. Hartmann and V. Meyer, Chem. Ber., 27, 426, 504 (1894).
(Benzene, iodoso-, diacetate)
C6HSI + CH3CO3H + CH3CO2H -»
(C6HsIOCOCH3)+(CH3COO)- + H20
Submitted by J. G. Shabefkin and H. Saltzman.1
Checked by J. Diekmann and В. C. McKusick.
1. Procedure
Caution! Avoid inhaling the vapor of peracetic acid or allowing the liquid to come into contact with the skin. The reaction is best carried out in a hood (Note 1).
The apparatus consists of a 200-ml. beaker equipped with a magnetic stirrer or any other type suitable for stirring a small volume of liquid. The flask is charged with 20.1 g. (0.10 mole) of iodobenzene 2 and is immersed in a water bath maintained at 30° (Note 2). Thirty-six grams (31 ml., 0.24 mole) of commercial 40% peracetic acid (Note 3) is added dropwise to the well-stirred iodobenzene over a period of 30-40 minutes. Stirring is continued for another 20 minutes at a bath temperature of 30°, during which time a homogeneous yellow solution is formed. Crystallization of iodosobenzene diacetate may begin during this period.
The beaker is chilled in an ice bath for 1 hour. The crystalline diacetate that separates is collected on a Buchner funnel and washed with three 20-ml. portions of cold water. After drying for 30 minutes on the funnel with suction, the diacetate is dried overnight in a vacuum desiccator containing calcium chloride (Note 4). The dried diacetate weighs 26.7 29.3 g. (83-91%) and melts at 158-159° with decomposition. The purity of the diacetate, determined by the titration method of Lucas, Kennedy, and Formo,3 is 97-98%, which is good enough for most purposes. The purity can be increased to 99-100% by a recrystallization from 5M acetic acid.
2. Notes
1. Rubber gloves should be worn when handling vessels containing peracetic acid, for traces of the liquid can cause severe irritation. Skin that has come into contact with peracetic acid should be washed immediately and treated with sodium bicarbonate. Details for the safe handling of peracetic acid are found in Bulletin 4 supplied by Buffalo Electrochemical Corp.
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