FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL/ COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"An Improved Process for producing 4-Nitrophthalic Acid and 4-Nitrophthalic Acid obtained thereof.
2. APPLICANT(S)
(a) NAME: SUDARSHAN CHEMICAL INDUSTRIES LTD.
(b) NATIONALITY: Indian Company registered under the provisions
of the Companies Act, 1956

(c) ADDRESS:

162, Wellesley road,
PUNE-411001, Maharashtra State, India

3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specificatif invention.

"describes the

COMPLETE
The following specification
particularly describes the invention and the
manner in which it is to be performed.

4. pES"CRIPTION (Description starts from page 2)

5. CLAIMS:

Given on a separate sheet

6. DATE AND SIGNATURE: Given at the end of last page of specification.
7. ABSTRACT OF THE INVENTION: Given on a separate sheet
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Title: An improved process for producing 4-Nitrophthalic acid and 4-Nitrophthalic acid obtained thereof.
Technical Field:
The present invention relates to a process for the preparation of 4-Nitrophthalic acid with high purity. More particularly, the present invention relates to a process for the preparation of 4-Nitrophthalic acid comprising a two-step process: (i) Nitration of Phthalimide with mixed acid and, (ii) Hydrolysis of resulting 4-Nitrophthalimide using dilute alkali.
The expression NPA used in the specification means the compound of the present invention.
The main object of the present invention is to provide an improved process for the preparation of 4-Nitrophthalic acid.
Another object of the present invention is to make 4-Nitrophthalic acid suitable for commercial production adopting safe nitrating conditions.
Still further object of the present invention is to provide improved isolation and purification process to make 4-Nitrophthalic acid with high purity.
Background and Prior art:
4-Nitrophthalic acid is a valuable intermediate for manufacturing various derivatives such as pigments, dyes and plasticizers, particularly for PVC, polyesters, polyamides, peptides, agricultural active substances [Compare German Patent Nos. 824,815, 935,964 and 936,944; U.S. Patent Nos. 2,412,817 and 2,491,455; CA, 47,9303d (1953), 53,11290f (1959), 66,116023b (1967), 69,107329r and 170330i (1968)].
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In the prior art, 4-Nitrophthalic acids have been prepared by several known methods. One such method is described in Organic Synthesis, Col. Volume II, John Wiley and Sons, New York, 1943, pages 457 to 459 which involve the nitration of phthalimide to give 4-nitrophthalimide in 13 parts concentrated sulphuric acid using 2 parts fuming nitric acid, at 10°C-15°C and hydrolyzing the latter.
In another method reported in Organic Syntheses, Col. Volume I, John Wiley and Sons, New York, 1932, pages 408 to 412f, wherein, phthalic acid or phthalic anhydride is nitrated gives an approximately 50/50 mixture of 4-nitrophthalic and 3-nitrophthalic acids. This reaction is a known procedure for the synthesis of 3-nitrophthalic acid, despite the low yields (28 to 31 per cent) of 3-nitrophthalic acid obtained. In preparing 3-nitrophthalic acid by this method, advantage is taken of the lower water solubility of 3-nitrophthalic acid. The latter material is then recovered by crystallization from water. 4-Nitrophthalic acid can be obtained from washings and other liquors after separation of 3-nitrophthalic acid via evaporation, esterification, separation of isomeric esters and subsequent hydrolysis of the separated ester of 4-nitrophthalic acid. This procedure would be expected to be laborious, costly and to result in low yields of 4-nitrophthalic acid.
U.S. Pat. No. 4,137,419 has disclosed a process for the preparation of 4-nitrophthalic acid which involves nitrating an indene, polyindene, dihydronaphthalene or polydihydronaphthalene with concentrated nitric acid and thereafter oxidizing said nitrated organic compound with dilute nitric acid, said nitration being conducted with an aqueous nitric acid solution having a concentration of from about 70 to about 95 wt. % at a temperature of 40° C. to about 90° C. and said oxidation being conducted with an aqueous nitric acid solution having a concentration from about 5 to about 50 wt. % at a temperature of about 135° C. to about 210° C.
U.S. Pat. No. 5,155,231 described a method for preparing nitrophthalic acid and anhydride by treating phthalic acid and anhydride in concentrated nitric acid
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allowing the mixture to react at a temperature of from about 20° C. to about the boiling point of the nitric acid to gives mixture of 3 and 4- nitrophthalic acid.
There are various disadvantages associated with the prior art methods for commercial success. However, it has now been found that the process reported in Organic Synthesis, Col. Volume II, John Wiley and Sons, New York, 1943, pages 457 to 459 can be further improved replacing fuming nitric acid (98%) which is being used in in large excess by aq. nitric acid (60-70%), optimizing concentrated sulphuric acid charge and alteration of purification techniques in subsequents steps to make process for commercial production with high purity product of present invention.
Deficiencies of Prior Art:
1. In the prior art process, nitration of phthalimide involves large excess of concentrated nitric and sulphuric and its effluent disposal is major concerns. In addition, in this process there is possibility of runway reaction in event of failure of cooling.
2. The other general process involving nitration of phthalic acid using concentrated sulphuric acid and/or concentrated nitric acid and provides varying mixture of nitrated products which needed rigorous isolation process to get product in pure form.
Description of the Present Invention:
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter.
The present invention relates to a process for the prepararion of pure 4-Nitrophthalic acid (NPA) of formula (I) in relatively high yields and purity. More particularly, the present invention relates to provide process, which is safer and less
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costly than prior processes for the preparation of pure 4-Nitrophthalic acid (NPA) suitable for commercial production in bulk. The present invention also discloses a process for the preparation of 4-Nitrophthalic acid (NPA) of formula (I) comprising of:
(a) Nitrating phthalimide of formula (II) using aq. Nitric acid in concentrated sulphuric
acid at 10-50°C to obtain 4-Nitrophthalimide of formula (III), and
(b) Hydrolyzing 4-Nitrophthalimide with dilute alkali at 80-100°C to obtain 4-
Nitrophthalic acid (NPA) of formula (I)



0,N
(II)

+ HNO, H2S°4

The nitric acid used in present invention for the nitration process should have a concentration of at least about 60% by weight and is preferably 70% concentration by weight. The amount of nitric acid used should be at least of the stoichiometric amount. Generally, the mole ratio of nitric acid to the phthalimide should be from about 1.0 to about 4.0, preferably from about 2 to 3.
According to the present invention, concentrated sulfuric acid is used as catalyst, solvent and dehydrating agent. The amount of sulfuric acid in weight ratio to phthalimide should be from 6 to 15, preferablely from about 8-10.
In present invention, dil alkai is used for hydrolysis of corresponding phthalimide and is selected from sodium or potassium hydroxide.
The process typically is carried out over a temperature range of about 10°-50°C, preferably 30°- 40°C for nitration and 80-100°C for hydrolysis of resultant nitrated product. Pressure normally is not an important process condition and the process
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therefore normally is performed at ambient pressure or slight under vacuum for safety reasons.
Example:
(a) Preparation of 4-nitrophthalimide
In a four- necked round-bottomed flask equipped with overhead stirrer, thermo well, and reflux condenser were placed phthalimide (0.026 kilo moles) and 5-8 gm concentrated sulphuric acid (98%) per 1 gm of phthalimide and heated reaction mixture under stirring to 35°C-40°C. In to the clear reaction mixture, 65-70% Nitric acid (3 to 5 mole equivalent) was added during 3 to 6 hour maintaining at 40-45 °C by means of ice salt mixture. After completion of addition, the reaction was maintained at 40-50° C for about 2-5 hours by means of external heating or cooling. The progress of the reaction was monitored by GLC. After completion, reaction mixture was cooled to 20-30 deg C, and poured in to 3-5ml chilled water per gm of sulphuric acid slowly at 15-20°C under stirring. The resultant product was filtered through suction, washed with water (3-5 ml per lgm sulphuric acid). The wet product was suspended in water, neutralized by dil sodium carbonate and filtered through suction. The wet product weighed 4.0 - 5.0kg (Yield 50-55% on dry basis) with 97-98% purity by qualitative High performance liquid chromatography (HPLC).
(b) Preparation of 4-nitrophthalic acid
In a four- necked round-bottomed flask equipped with overhead stirrer, thermo well, and reflux condenser were placed 4-nitrophthalimide (0.0135 kilo moles) and 13% wt/wt sodium hydroxide solution (1.5to 2mole equivalent). The reaction mixture was heated to 80°C-100°C and maintained at same temperature for 1-5 hours under stirring. The progress of the reaction was monitored by HPLC. After completion, reaction mixture was added 30% Hydrochloric acid (2-2.5 mole equivalent) at 80-100°C and maintained reaction at same temperature for 1-3 hours. The reaction mixture was cooled to 10°-20°C and extracted with ethyl acetate thrice under stirring. The combined organic layer contained product and ethyl acetate was washed with 30% sodium chloride solution and separated organic layer was treated with activated carbon at 10-30°C under stirring. After
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removal of carbon through filtration, ethyl acetate was distilled out under reduced pressure and toluene was added to get product. The resultant slurry mass was filtered and dried to give light yellow to white crystalline product in 90-95% yield (1.45 -1.55kg) with 98% purity by qualitative High performance liquid chromatography (HPLC).
The embodiments of the invention as described above and the method disclosed of the present invention will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention, which is defined, by the scope of the following claims.
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We Claim:
1. A process of preparing 4-Nitrophthalic acid (NPA) of formula (I) comprising of:
(a) Nitrating phthalimide of formula (II) using aq. Nitric acid in concentrated sulphuric
acid at 10-50°C to obtain 4-Nitrophthalimide of formula (III), and
(b) Hydrolyzing 4-Nitrophthalimide with dilute alkali at 80-100°C to obtain
4-Nitrophthalic acid (NPA) of formula (I)



0,N
(ID

NH

+ HNO, H2S°4

2. A process of preparing 4-Nitrophthalic acid (NPA) of formula (I) as claimed in claim 1, wherein 60-70 wt % concentration of Nitric acid used in 3-5-mole equivalent.
3. A process as claimed in claim 1, wherein the concentrated sulphuric acid is used in 5-8-weight ratio to the phthalimide.
4. A process as claimed in claim 1, wherein nitration is carried out at 10-50°C.
5. A process as claimed in claim 1, wherein sodium/potassium hydroxide used in 1.5 to
2.0- mole equivalents.
6. A process as claimed in claim 1, wherein hydrolysis reaction carried out at 80-100°C.
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7. A process as claimed in claim 1, wherein all reactions performed is at atmospheric pressure.
8. A process of as claimed in claim 1 substantially as herein described with reference to the example.
9. 4-Nitrophthalic acid (NPA) prepared by the process as claimed in claims 1 to 8

Abstract
The present invention relates to the process for the preparation of 4-Nitrophthalic acid comprising of the following steps:
(a) Nitrating phthalimide of formula (II) using aqueous Nitric acid in concentrated sulphuric acid at 10-50°C to obtain 4-Nitrophthalimide of formula (III), and
(b) Hydrolyzing 4-Nitrophthalimide with dilute alkali at 80-100°C to obtain 4-Nitrophthalic acid (NPA) of formula (I)



02N
(ID

+ HNO, H2S°4

The present invention is much safer and useful to make 4-Nitrophthalic acid suitable for commercial production adopting safe nitrating conditions.