Org. Synth. 1939, 19, 6
Submitted by C. F. H. Allen and G. H. W. McKee.
Checked by W. W. Hartman and A. Weissberger.
(A) N-Phenylanthranilic Acid.—In a 1-l. round-bottomed flask fitted with an air-cooled condenser, a mixture of 155 g. (1.66 moles) of aniline, 41 g. (0.26 mole) of o-chlorobenzoic acid (Note 1), 41 g. (0.3 mole) of technical anhydrous potassium carbonate, and 1 g. of copper oxide is refluxed for two hours, using an oil bath. The excess aniline is removed by distillation with steam (about three hours is required), and 20 g. of decolorizing carbon (Note 2) is added to the brown residual solution. The mixture is boiled for fifteen minutes and filtered by suction. The filtrate is added, with stirring, to a mixture of 30 cc. of concentrated hydrochloric acid and 60 cc. of water. The precipitated acid is filtered with suction when cold. After drying to constant weight in the air, the yield is 46–52 g. (82–93 per cent of the theoretical amount) of a nearly white product; m.p. 179–181° with preliminary shrinking (Note 3), (Note 4), and (Note 5).
(B) Acridone.—In a 500-cc. flask a solution of 42.7 g. (0.2 mole) of N-phenylanthranilic acid (Note 6) in 100 cc. of concentrated sulfuric acid (sp. gr. 1.84) is heated on a boiling water bath for four hours and then poured into 1 l. of boiling water. Spattering is minimized by allowing the solution to run down the wall of the container. The yellow precipitate is filtered after boiling for five minutes, and the filtrate is saved (Note 7). The moist solid is boiled for five minutes with a solution of 30 g. (0.28 mole) of sodium carbonate in 400 cc. of water, collected with suction (Note 8), and washed well with water. After drying in the air the crude acridone weighs 35.5–37.5 g. (91–96 per cent of the theoretical amount) and melts at 344–346° (Note 9). This material is pure enough for many purposes; it may be recrystallized from a mixture of aniline and acetic acid, using 10 cc. of aniline and 25 cc. of acetic acid for every 2 g. of solid. The recovery is about 90 per cent, and the recrystallized product melts at 348–352° (Note 10).
Sixty grams of technical o-chlorobenzoic acid
is dissolved in 200 cc. of hot water containing 20 g. of sodium carbonate
, 10 g. of decolorizing carbon
is added, and, after boiling for ten minutes, the mixture is filtered by suction. The filtrate is added to hydrochloric acid
prepared by diluting 31 cc. of the concentrated acid
with an equal volume of water. The air-dried product weighs 41 g.
and is used directly. This purification is essential to obtain a good yield and a product of good quality. If it is omitted, a blue to black acid results, from which the color is removed only with difficulty.
Directions for preparing o-chlorobenzoic acid
by the oxidation of o-chlorotoluene
are given on p. 135
Ordinary animal charcoal and Darco gave equally good results.
decomposes slowly at elevated temperatures. Before the melting point is reached, there is considerable preliminary shrinkage. If the "dip method" is used, the melting point is 182–183°
. The literature values vary from 181° to 184°
for the pure acid.
This acid is pure enough for all ordinary purposes. The melting point is only slightly raised by dissolving 5 g.
in 100 cc. of water containing 2.5 g. of sodium carbonate
, adding 2.5 g. of decolorizing carbon
, boiling for five minutes, filtering, and acidifying. The recovery is 4.6 g.
If the product is colored this procedure must be followed to get acridone
of light color.
For recrystallization, 5 g.
of the acid is dissolved in 25 cc. of boiling alcohol
and 5 cc. of water added. The recovery is 4.8 g.
, and the melting point is 182–183°
. Acetic acid (2 cc. per gram)
may be substituted for alcohol; it is more convenient for recrystallizing large quantities.
The N-phenylanthranilic acid
may be used without recrystallization if it has been prepared from purified o-chlorobenzoic acid
. If not, the crude N-phenylanthranilic acid
must be decolorized as described in (Note 4)
; otherwise a greenish acridone
is obtained which, however, has the proper melting point.
On standing overnight, the filtrate deposits 1 6 to 2 g.
of a very impure product which melts at about 315°
On acidification of the filtrate, a little (1.5–2 g.
) N-phenylanthranilic acid
is always precipitated.
The crude acridone
shrinks in a capillary tube
at 330–335° and melts to a dark-colored liquid at 344–346°
may also be used for recrystallization; 1 g. of acridone
requires 120 cc. of solvent and yields 0.75 g.
of material melting at 354°
, using a Berl-Kullman copper block
The practical methods of preparation of N-phenylanthranilic acid
are the action of aniline
on o-chloro- or o-bromobenzoic acid
or the action of bromobenzene
on anthranilic acid
, 6 copper or its salts
being used in both instances.
The only method of preparative value for acridone
is by ring closure of N-phenylanthranilic acid
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
copper or its salts
o-chloro- or o-bromobenzoic acid
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
hydrochloric acid (7647-01-0)
acetic acid (64-19-7)
sodium carbonate (497-19-8)
decolorizing carbon (7782-42-5)
Anthranilic Acid (118-92-3)
copper oxide (1317-38-0)
isoamyl alcohol (123-51-3)
N-Phenylanthranilic acid (91-40-7)
o-Chlorobenzoic acid (118-91-2)
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