DESC:FIELD
The present disclosure relates to a process for the preparation of 2,3-dichloro-6-nitroaniline.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
2,3-dichloro-6-nitroaniline is an important intermediate in the preparation of pesticides. The structural representation of 2,3-dichloro-6-nitroaniline is given as formula (I) below:

(I)
Conventional methods for the preparation of 2,3-dichloro-6-nitroaniline provide 2,3-dichloro-6-nitroaniline with di-nitro impurities. Further, these conventional methods require further purification of 2,3-dichloro-6-nitroaniline. Furthermore, if not purified the impurities in 2,3-dichloro-6-nitroaniline may affect the efficacy, safety, and stability of the final product produced by using 2,3-dichloro-6-nitroaniline. The yield/productivity of 2,3-dichloro-6-nitroaniline, obtained from the known processes is considerably low.
Therefore, there is felt a need to provide a process for the preparation of 2,3-dichloro-6-nitroaniline that mitigates the aforestated drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of 2,3-dichloro-6-nitroaniline.
Yet another object of the present disclosure is to provide a process for the preparation of 2,3-dichloro-6-nitroaniline with a comparatively better yield.
Still another object of the present disclosure is to provide a simple and cost-effective process for the preparation of 2,3-dichloro-6-nitroaniline.
Another object of the present disclosure is to provide an environment-friendly and commercially scalable process for the preparation of 2,3-dichloro-6-nitroaniline.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for the preparation of 2,3-dichloro-6-nitroaniline. The process comprises mixing a predetermined amount of 1,2,3-trichloro benzene in at least one first fluid medium followed by adding a mineral acid and heating at a first predetermined temperature to obtain a mixture. 1,2,3-trichloro benzene present in the mixture is nitrated by adding a nitrating agent slowly for a first predetermined time period at a second predetermined temperature to obtain a reaction mixture comprising 2,3,4-trichloro nitrobenzene and 3,4,5-trichloro nitrobenzene. The reaction mixture comprising 2,3,4-trichloro nitrobenzene and 3,4,5-trichloro nitrobenzene is aminated in a second fluid medium using ammonia gas to obtain a reaction mass. The so obtained reaction mass is heated at a third predetermined temperature for a second predetermined time period at a predetermined pressure to obtain a first slurry. The first slurry is washed with water, followed by filtration to obtain a wet cake. The wet cake is dried at a temperature in the range of 60°C to 85°C to obtain a crude 2,3-dichloro-6-nitroaniline. The crude 2,3-dichloro-6-nitroaniline is purified to obtain a pure 2,3-dichloro-6-nitroaniline.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described herein. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
2,3-dichloro-6-nitroaniline is an important intermediate in the preparation of pesticides. The structural representation of 2,3-dichloro-6-nitroaniline is given as formula (I) below:

(I)
Conventional methods for the preparation of 2,3-dichloro-6-nitroaniline provide 2,3-dichloro-6-nitroaniline with di-nitro impurities. Further, these conventional methods require further purification of 2,3-dichloro-6-nitroaniline. Furthermore, if not purified the impurities in 2,3-dichloro-6-nitroaniline may affect the efficacy, safety, and stability of the final product produced by using 2,3-dichloro-6-nitroaniline. The yield/productivity of 2,3-dichloro-6-nitroaniline obtained from the known processes is considerably low.
The present disclosure provides an improved process for the preparation of 2,3-dichloro-6-nitroaniline.
The process of the present disclosure is simple, environment friendly, economical, and results in improved yields and higher purity of 2,3-dichloro-6-nitroaniline and is commercially scalable.
In an aspect of the present disclosure, there is provided a process for preparing
2,3-dichloro-6-nitroaniline.
The process of the preparation of 2,3,4 – trichloro nitrobenzene is detailed below.
In a first step, a predetermined amount of a first fluid medium is mixed with 1,2,3–trichloro benzene followed by adding a mineral acid under stirring at a first predetermined temperature to obtain a mixture.
In an embodiment of the present disclosure, the first fluid medium is at least one selected from ethylene dichloride (EDC), and methylene dichloride (MDC). In an exemplary embodiment of the present disclosure, the first fluid medium is ethylene dichloride.
In an embodiment of the present disclosure, the first predetermined temperature is in the range of 30°C to 60°C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 40°C.
In an embodiment of the present disclosure, the mineral acid is sulphuric acid.
In a second step, to the mixture, a predetermined amount of nitrating agent is added slowly for a first predetermined time period at a second predetermined temperature for nitrating 1,2,3–trichloro benzene to obtain a reaction mixture comprising a mixture of 2,3,4 – trichloro nitrobenzene and 3,4,5 – trichloro nitrobenzene.
In an embodiment of the present disclosure, the use of EDC provides a clear solution at a lower temperature, which avoids further heating. Further, since the nitration is performed at a lower temperature (30°C to 60°C) formation of dinitro impurity can be avoided.
In an embodiment of the present disclosure, the nitrating agent is nitric acid.
In an embodiment of the present disclosure, the first predetermined time period is in the range of 90 minutes to 180 minutes. In an exemplary embodiment of the present disclosure, the first predetermined time period is 120 minutes.
In an embodiment of the present disclosure, the second predetermined temperature is in the range of 30°C to 60°C. In an exemplary embodiment of the present disclosure, the second predetermined temperature is 40°C to 45°C.
In an embodiment of the present disclosure, a weight ratio of 1,2,3 – trichloro benzene to the nitrating agent is in the range of 1:0.3 to 1:0.5. In an exemplary embodiment of the present disclosure, the weight ratio of 1,2,3 – trichloro benzene to the nitrating agent is 1:0.42.
A schematic representation for the preparation of 2,3,4 – trichloro nitrobenzene is given as scheme A.

SCHEME A
In a third step, the reaction mixture of 2,3,4 – trichloro nitrobenzene and 3,4,5 – trichloro nitrobenzene are aminated by using ammonia gas to obtain a reaction mass. The so obtained reaction mass is heated at a third predetermined temperature for a second predetermined time period at a predetermined pressure, wherein the temperature and pressure are gradually increased to obtain a first slurry.
In an embodiment of the present disclosure, the second fluid medium is at least one selected from mono chlorobenzene (MCB), O-dichloro benzene (ODCB), and Xylene. In an exemplary embodiment of the present disclosure, the second fluid medium is mono chlorobenzene (MCB).
In an embodiment of the present disclosure, the third predetermined temperature is in the range of 90°C to 150°C. In an exemplary embodiment of the present disclosure, the third predetermined temperature is 100°C. In another exemplary embodiment of the present disclosure, the third predetermined temperature is 110°C. In yet another exemplary embodiment of the present disclosure, the third predetermined temperature is 120°C.
In an embodiment of the present disclosure, the second predetermined time period is in the range of 20 hours to 30 hours. In an exemplary embodiment, the second predetermined time period is 24 hours.
In an embodiment of the present disclosure, the predetermined pressure is in the range of 20 Kg/Cm2 to 30 Kg/Cm2. In an exemplary embodiment of the present disclosure, the predetermined pressure is 25 Kg/Cm2. In another exemplary embodiment of the present disclosure, the predetermined pressure is 26 Kg/Cm2.
In a fourth step, the slurry is washed with water, and filtered to obtain a wet cake and a filtrate. The so obtained wet cake is to be dried at a temperature in the range 60°C to 85°C to obtain a crude 2,3-dichloro-6-nitroaniline. In an exemplary embodiment of the present disclosure, the drying temperature is 65°C.
A schematic representation for the preparation of 2,3-dichloro-6-nitroaniline is given as scheme B.

SCHEME B
In a fifth step, the crude 2,3-dichloro-6-nitroaniline is mixed with a third fluid medium followed by heating at a fourth predetermined temperature to obtain a solution. The solution is cooled to a fifth predetermined temperature to obtain a second slurry. The second slurry is filtered to obtain a wet cake and filtrate. The so obtained wet cake is washed with a fourth fluid medium and dried to obtain pure 2,3-dichloro-6-nitroaniline.
In an embodiment of the present disclosure, the third fluid medium and fourth fluid medium is independently selected from dimethylformamide (DMF), methanol, N-Methyl pyrrolidone (NMP), Dimethylacetamide (DMAc), and acetone.
In an embodiment of the present disclosure, the fourth predetermined temperature is in the range of 80°C to 120°C. In an exemplary embodiment of the present disclosure, the fourth predetermined temperature is 100°C.
In an embodiment of the present disclosure, the fifth predetermined temperature is in the range of 20°C to 30°C. In an exemplary embodiment of the present disclosure, the fifth predetermined temperature is 25°C.
The present disclosure provides a simple and economic process for the preparation of 2,3-dichloro-6-nitroaniline which provides a comparatively higher yield of the product with greater purity.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments are scalable to industrial/commercial process.
EXPERIMENTAL DETAILS
EXPERIMENT 1: Preparation of 2,3,4-Trichloro Nitrobenzene
400 ml of ethylene dichloride (EDC) and 181.5 gm of 1,2,3-trichloro benzene were charged into a reactor followed by adding 110 gm of 98% H2SO4 under stirring at 40°C to obtain a mixture. To the mixture 77 gm of 98% HNO3 was slowly added for 2 hours maintaining the temperature at 40°C to 45°C to obtain a reaction mixture comprising 2,3,4 – trichloro nitrobenzene and 3,4,5 – trichloro nitrobenzene (having a GLC ratio of 96-97:3-4). The reaction was monitored by GLC analysis and the reaction was stopped when the sample showed the absence of 1,2,3-trichloro benzene.
The reaction mixture was drowned into ice water to obtain a biphasic layer i.e. EDC layer and aqueous layer. The EDC layer was separated and 100 ml of NaHCO3 was added for achieving neutral pH to obtain a resultant mass comprising a mixture of 2,3,4 – trichloro nitrobenzene and 3,4,5 – trichloro nitrobenzene. The resultant mass was dried under vacuum at 50°C to 55°C to obtain 2,3,4 – trichloro nitrobenzene (97%) and 3,4,5 – trichloro nitrobenzene (3%).
EXPERIMENT 2: Preparation of 2,3-dichloro-6-nitroaniline

1000 ml of monochlorobenezene (MCB) and 226.5 gm of a mixture of 2,3,4-trichloro nitrobenzene (97%) and 3,4,5-trichloro nitrobenzene (3%) obtained in Experiment 1 were charged into a pressure reactor followed by passing 136 gm of NH3 gas at 30°C to obtain a reaction mass. The reaction mass was heated to 100°C for 8 hours at a pressure of 25 Kg/Cm2 followed by gradually increasing the temperature to 110°C and further to 120°C maintaining independently for 8 hours at a pressure of 25 Kg/Cm2 and 26 Kg/Cm2 respectively to obtain a first slurry. The so obtained first slurry was mixed with 750 ml of water, and the MCB in the slurry was completely removed by steam distillation to obtain a resultant mass. The resultant mass was cooled to 30°C, filtered, and washed with water (250 ml) to obtain a first filtrate and a first wet cake. The so obtained first wet cake was dried at 65°C to obtain a crude 2,3-dichloro-6-nitroaniline (crude crop). The GLC of the solids are provided below
2,3-Dichloro-6-nitroaniline Trichloro nitro benzene Impurity Diamino nitro chloro benzene
95% Nil 2% 3%

Purification:
100 gm of the crude 2,3-dichloro-6-nitroaniline (crude crop) and 300 ml of 70% aq. DMF (30% water v/v) were charged into a reactor and heated to 100°C to obtain a clear solution. The solution was cooled to 25°C to obtain a second slurry. The second slurry was filtered to obtain a second wet cake and a second filtrate. The so obtained second wet cake was washed with 50 ml 70% aqueous DMF and re-slurried with 200 ml of water to obtain a third slurry. The so obtained third slurry was filtered to obtain a third wet cake and a third filtrate. The wet cake was washed with 100 ml of water and dried in an oven to obtain a pure 2,3-Dichloro-6-nitroaniline (89 gm).
The GLC of the solids are provided below
2,3-Dichloro-6-nitroaniline Trichloro nitro benzene Impurity Diamino nitro chloro benzene
99.4% Nil 0.1% 0.5%

TECHNICAL ADVANCEMENT
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for the preparation of 2,3-dichloro-6-nitroaniline:
• avoids the formation of di-nitro impurity (2,3,4-trichloro-1,3 dinitrobenzene);
• a simple and economical process for the preparation of 2,3-dichloro-6-nitroaniline;
• use of EDC solvent provides a clear solution without heating; and
• provides 2,3-dichloro-6-nitroaniline having comparatively high purity and high yield.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:WE CLAIM:
1. A process for preparing 2,3-dichloro-6-nitroaniline represented by formula (I):

(I)
wherein said process comprising the following steps:
a) mixing a predetermined amount of 1,2,3-trichloro benzene in at least one first fluid medium followed by adding a mineral acid and heating at a first predetermined temperature to obtain a mixture;
b) nitrating 1,2,3-trichloro benzene from said mixture by adding a predetermined amount of nitrating agent slowly for a first predetermined time period at a second predetermined temperature to obtain a reaction mixture comprising 2,3,4-trichloro nitrobenzene and 3,4,5-trichloro nitrobenzene;
c) aminating said reaction mixture comprising 2,3,4-trichloro nitrobenzene and 3,4,5-trichloro nitrobenzene in a second fluid medium by using ammonia gas to obtain a reaction mass;
d) heating said reaction mass at a third predetermined temperature for a second predetermined time period at a predetermined pressure to obtain a first slurry;
e) washing said first slurry with water, followed by filtration to obtain a wet cake;
f) drying said wet cake at a temperature in the range of 60°C to 85°C to obtain a crude 2,3-dichloro-6-nitroaniline; and
g) purifying said crude 2,3-dichloro-6-nitroaniline to obtain a pure 2,3-dichloro-6-nitroaniline.
2. The process as claimed in claim 1, wherein purification of said crude 2,3-dichloro-6-nitroaniline comprising the following steps:
a) mixing said crude 2,3-dichloro-6-nitroaniline with a third fluid medium followed by heating at a fourth predetermined temperature to obtain a solution;
b) cooling said solution to a fifth predetermined temperature to obtain a second slurry;
c) filtering said second slurry to obtain a wet cake and filtrate; and
d) washing said wet cake with said fourth fluid medium followed by drying to obtain said pure 2,3-dichloro-6-nitroaniline.
3. The process as claimed in claim 1, wherein said first fluid medium is at least one selected from ethylene dichloride (EDC), and methylene dichloride (MDC).
4. The process as claimed in claim 1, wherein said mineral acid is sulphuric acid.
5. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 30°C to 60°C.
6. The process as claimed in claim 1, wherein said nitrating agent is nitric acid.
7. The process as claimed in claim 1, wherein said first predetermined time period is in the range of 90 minutes to 180 minutes.
8. The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 30°C to 60°C.
9. The process as claimed in claim 1, wherein a weight ratio of 1,2,3 – trichloro benzene to said nitrating agent is in the range of 1:0.3 to 1:0.5.
10. The process as claimed in claim 1, wherein said second fluid medium is at least one selected from the group consisting of monochlorobenezene (MCB), O-dichloro benzene (ODCB), and Xylene.
11. The process as claimed in claim 1, wherein said third predetermined temperature is in the range of 90°C to 150°C.
12. The process as claimed in claim 1, wherein said second predetermined time period is in the range of 20 hours to 30 hours.
13. The process as claimed in claim 1, wherein said predetermined pressure is in the range of 20 Kg/Cm2 to 30 Kg/Cm2.
14. The process as claimed in claim 2, wherein said third fluid medium and said fourth fluid medium is independently selected from aqueous dimethylformamide (DMF), methanol, N-Methyl pyrrolidone (NMP), Dimethylacetamide (DMAc), and acetone.
15. The process as claimed in claim 2, wherein said fourth predetermined temperature is in the range of 80°C to 120°C.
16. The process as claimed in claim 2, wherein said fifth predetermined temperature is in the range of 20°C to 30°C.

Dated this 08th day of November, 2022

MOHAN RAJKUMAR DEWAN,
IN/PA – 25,
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI