Organic Syntheses, Coll. Vol. 5, p.805 (1973); Vol. 42, p.77 (1962).
MONOPERPHTHALIC ACID
[Phthalic monoperoxy acid]
Submitted by George B. Payne
1
Checked by K. Nagarajan and John D. Roberts.
1. Procedure
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].
In a
1-l. round-bottomed flask equipped with a mechanical stirrer and cooled in an ice-salt bath is placed a solution of
62 g. (0.5 mole) of sodium carbonate monohydrate in 250 ml. of water. This is cooled to 0°, and
69 g. (63 ml., 0.6 mole) of 30% hydrogen peroxide (Note 1) is added in one portion. With the temperature at −5 to 0°,
74 g. (0.5 mole) of phthalic anhydride (Note 1) which has been pulverized to pass a 14-mesh sieve is added
(Note 2).
The reaction mixture is stirred vigorously at −5 to 0° for 30 minutes, then the resulting solution or suspension
(Note 3) is poured into a
2-l. separatory funnel, shaken with
350 ml. of ether (Note 4), and carefully acidified with an ice-cold solution of
30 ml. of concentrated sulfuric acid in 150 ml. of water. The liberated
monoperphthalic acid is extracted into the
ether and removed completely from the water by extraction with two more
150-ml. portions of ether. The combined
ether extracts are washed with two
200-ml. portions of 40% ammonium sulfate solution and dried overnight in a refrigerator over
50 g. of anhydrous magnesium sulfate.
The peracid content is determined by adding
30 ml. of 20% potassium iodide solution to 2 ml. of the peracid solution and, after 10 minutes, titrating the liberated
iodine with 0.1
N thiosulfate. The yield is
71–78 g. (
78–86% based on
phthalic anhydride).
If crystalline
monoperphthalic acid is desired, it may be prepared as described earlier.
2
2. Notes
2.
Fieser and Fieser
3 recommend that the
phthalic acid be recrystallized from
benzene rather than pulverized.
3.
The
sodium salt of monoperphthalic acid may precipitate during the reaction.
4.
The
ether may be used, along with a
small amount of cold water, to effect a quantitative transfer of the suspension from reaction vessel to separatory funnel.
3. Discussion
The methods of preparation, properties, analysis, and safe handling of monoperphthalic acid have been reviewed.
84. Merits of Preparation
The Böhme procedure
2,5 for preparing perphthalic acid from
phthalic anhydride and
hydrogen peroxide is sensitive to slight variations in the experimental conditions.
6,7 The present method gives reproducible yields with quite short reaction times.
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