Organic Syntheses, CV 5, 665
Submitted by J. G. Sharefkin and H. Saltzman
1.
Checked by E. J. Corey and C. P. Lillya.
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).
Iodoxybenzene explodes if heated to 230°.
A
500-ml. three-necked flask fitted with
reflux condenser,
stirrer, and
dropping funnel and containing
20.4 g. (0.10 mole) of iodobenzene2 is immersed in an
oil bath maintained at 35°.
Seventy-five grams (65 ml., 0.50 mole) of commercial 40% peracetic acid (Note
1) is added with vigorous stirring over a 30-minute period. Solid may begin to form before all the
peracetic acid has been added, but, although this may slow down the stirring, it does not decrease the yield or cause a rise in temperature.
After all the
peracetic acid has been added, the reaction mixture is diluted with 80 ml. of water and heated from 35° to 100° over a 20-minute period (Note
2). It is then kept at 100° for 45 minutes. The flask is cooled to 0–5° in an
ice bath, and the solid
iodoxybenzene is collected on a
Büchner funnel and air-dried with suction for 1 hour. Additional material is obtained by concentrating the filtrate to one-fourth of its volume
(Caution! (Note 3)). The two crops of crude
iodoxybenzene are combined and dried overnight in a
desiccator; weight
19.6–20.5 g.; m.p.
230°
(Caution! Explodes!). Iodometric titration
3 shows the purity to be about 94% (Note
4).
Purification of the crude
iodoxybenzene is effected by grinding it to a powder in a
mortar, macerating it with
70 ml. of chloroform, and separating the solid by filtration. The
chloroform extraction is repeated and the solid is dried; weight
17–19 g. (
72–80%); purity 99.0–99.9% by iodometric titration.
3
2. Notes
2. If the temperature of the bath is not raised slowly, foaming is difficult to control. Although the gradual rise in temperature causes considerable foaming, the reaction mixture remains within the flask.
3. The filtrate must not be evaporated to dryness because
iodoxybenzene explodes when heated.
3. Discussion
4. Merits of the Preparation
Iodoxyarenes are useful in the preparation of
iodonium salts, Ar
2I
+X
−.
15
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