Organic Syntheses, Coll. Vol. 5, p.665 (1973); Vol. 43, p.65 (1963).
Caution! Reactions and subsequent operations involving peracids and peroxy compounds should be run behind a safety shield. For relatively fast reactions, the rate of addition of the peroxy compound should be slow enough so that it reacts rapidly and no significant unreacted excess is allowed to build up. The reaction mixture should be stirred efficiently while the peroxy compound is being added, and cooling should generally be provided since many reactions of peroxy compounds are exothermic. New or unfamiliar reactions, particularly those run at elevated temperatures, should be run first on a small scale. Reaction products should never be recovered from the final reaction mixture by distillation until all residual active oxygen compounds (including unreacted peroxy compounds) have been destroyed. Decomposition of active oxygen compounds may be accomplished by the procedure described in Korach, M.; Nielsen, D. R.; Rideout, W. H. Org. Synth. 1962, 42, 50 (Org. Synth. 1973, Coll. Vol. 5, 414). [Note added January 2011].
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)
explodes if heated to 230°.
A 500-ml. three-necked flask
fitted with reflux condenser
, 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°
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.
); purity 99.0–99.9% by iodometric titration.3
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.
The filtrate must not be evaporated to dryness because iodoxybenzene
explodes when heated.
4. Merits of the Preparation
Iodoxyarenes are useful in the preparation of iodonium
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