PREPARATION OF 2-(PHENYLAMINO)BENZOIC ACID
increase in the reaction temperature did not lead to
1513
α, mol
higher target product yield.
Under thermal heating, other conditions being the
same, the 2-[(carboxymethyl)(phenyl)amino]benzoic
acid preparation took no less than 6 hours.
It should be noted that the prepared product should
have been dried at 90°C with the forced air circulation,
as in the humid environment 2-[(carboxymethyl)
(
phenyl)amino]benzoic acid turned green.
τ, min
To compare the two reported syntheses, 2-
(carboxymethyl)(phenyl)amino]benzoic acid was also
prepared in the aqueous medium, in the absence of
organic co-solvents.
Fig. 2. Kinetic curves of 2-[(carboxymethyl)(phenyl)amino]-
benzoic acid accumulation at various temperatures, °С: (1)
[
9
0, (2) 110, and (3) 100.
EXPERIMENTAL
In the absence of n-butanol, other conditions being
the same (reagents ratio and concentrations, timing,
irradiation power, etc), 2-[(carboxymethyl)(phenyl)-
amino]benzoic acid yield did not exceed 63%, thus it
was not rational to prepare 2-[(carboxymethyl)(phenyl)-
amino]benzoic acid in the aqueous medium. With
potassium carbonate changed to Na CO or NaHCO ,
The initial and final products purity was checked by
thin layer chromatography using the high-efficiency
Sorbfil plates (PTSKh-AF-V-UF). Chromatograms
were analyzed using Sorbfil densitometer and Sorbfil
.8 software. The following eluents were used:
benzene–acetic acid 10:0.8 in the case of 2-(phenyl-
amino)benzoic acid and toluene–ethanol–acetic acid
1
2
3
3
the target product was obtained in the form of yellow
oily uncrystallizable substance, and it was not possible
to separate the pure target product from it; thus, this
synthesis in the presence of sodium (hydrogen)
carbonate was not of practical interest.
1
0:7:0.1 in the case of 2-[(carboxymethyl)(phenyl)-
amino]benzoic acid.
Composition and structure of the products were
confirmed by thin layer chromatography (comparison
with standard samples) and IR spectroscopy (IR-200
Nicolet, KBr), as well as by determination of some
physicochemical constants.
The kinetics of 2-[(carboxymethyl)(phenyl)amino]
benzoic acid formation was studied as described above
for 2-(phenylamino)benzoic acid synthesis. The results
obtained are shown in Fig. 2.
2
-[(Carboxymethyl)(phenyl)amino]benzoic acid.
Similarly to the discussed above, the rate of 2-
(carboxymethyl)(phenyl)amino]benzoic acid forma-
1
5.6 g (0.1 mol) of 2-chlorobenzoic acid was added in
[
several portions to 11.5 ml of cold aqueous potassium
hydroxide (35 wt.%), and the mixture was stirred at the
highest stirring rate in MARS during 20 min at 45°С.
Then, 0.5 g of Cu Cl , 9.2 ml (0.1 mol) of aniline, and
.24 g (0.1 mol) of NaHCO or 5.3 g (0.6 mol) of
tion in the initial stage was not sensitive to the reaction
temperature. At higher conversion, the target product
yield first increased with increasing temperature (Fig. 2,
curves 1, 3), further the temperature increase led to
lower target product yield (Fig. 2, curves 2, 3), likely
due to the side reactions enhancement.
2
2
9
3
Na CO were added. The temperature was raised from
2
3
3
0°C to 80°C within 40 min, further temperature
program was set according to the data given in Table 1.
Thus, in this work, the optimal conditions of
preparation of 2-(phenylamino)benzoic acid and 2-
[
(carboxymethyl)(phenyl)amino]benzoic acid via
After the reaction was completed, 10 ml of aqueous
potassium hydroxide (10 wt.%) was added to the
reactor. The mixture was boiled with activated carbon,
and filtered. The filtrate was acidified with hydro-
chloric acid. The precipitated product was filtered off
and washed with hot water. Mp 181–182°C (technical
product), 182–183°C (glacial acetic acid) (mp 183–
Ullmann reaction under microwave irradiation were
found. Performing the reactions under the selected
conditions led to higher yield and purity of the pro-
ducts as compared to those under conventional thermal
heating; in the case of 2-(phenylamino)benzoic acid
preparation the process was also more environmentally
friendly that the conventional one [4].
–
1
184°C [6]). IR spectrum, ν, cm : 3340 (N–H); 3300–
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 8 2013