A processes for the preparation of benzonitrile compounds from the corresponding benzotrichloride compounds

Abstract

The present invention discloses a process for the preparation of benzonitrile compounds of Formula (I) from the corresponding benzotrichloride compounds of Formula (II).

Description

[0001]FIELD OF THE INVENTION: The present invention relates to a process for the preparation of benzonitrile compounds. More particularly, the present invention relates to a process for the preparation of benzonitrile compounds of Formula (I) by nitrilation of the corresponding benzotrichloride compounds of Formula (II). BACKGROUND OF THE INVENTION: The benzonitriles are products known in the art and used as intermediates particularly in the preparation of dyes, pharmaceuticals and agrochemicals. J. Am. Chem. Soc. 1930, 52, 7, 2951–2954 discloses a process for preparing ortho- chlorobenzonitrile from ortho-chloro benzo trichloride using ammonium chloride. The drawback with this process is that it requires a closed tube and an elevated temperature of 210 to 220 °C thus making it energy intensive. Further, at least 60% excess of ortho-chloro benzo trichloride is used for consuming all of the ammonium chloride. Also, the process results in the polymerization of benzonitrile and tetraphenylmethane is obtained as a by-product. EP441004 discloses a process for preparing ortho-chlorobenzonitrile from ortho-chloro benzo trichloride using copper (II) chloride or zinc chloride as a catalyst and ammonium chloride. The drawback associated with this process is that the reaction is carried out at an elevated temperature of more than 210 °C and thereby making it energy intensive. Also, as the metal salts such as copper (II) chloride or zinc chloride are used it leads to the generation of unwanted solid waste significantly. WO2022091014 discloses a process for the preparation of ortho-chloro benzonitrile, wherein the process comprises the reaction of 2-chlorobenzotrichloride with ammonium chloride in the presence of water, sulfuric acid and zinc acetate at room temperature. The reaction is carried out at 180 °C to 200 °C for 16 hrs. The drawbacks associated with this process are the reaction was carried out at elevated temperature and the reaction resulted in less purity of ortho-chloro benzonitrile (96%). JP2652563 discloses a process for the preparation of ortho-chlorobenzonitrile and ortho- chlorobenzoyl chloride from ortho-chlorobenzotrichloride and ortho-chlorobenzamide using concentrated sulfuric acid as catalysts in the presence of ortho-chlorotoluene solvent. The reaction mixture was heated to 140oC. Further, the reaction solution was treated with ammonia gas to convert the acid chloride product into its corresponding acid amide. The typical reaction involves the conversion of ortho-chlorobenzotrichloride to ortho-chlorobenzoyl chloride and ortho-chlorobenzamide to ortho-chlorobenzonitrile. Thus, there is a need to develop a process for the preparation of benzonitrile compounds which obviates at least one problem of prior art processes, such as impure benzonitrile, specific reaction set-up, polymerization and cost-effectiveness. The inventors of the present invention have found a simple, industrially feasible and advantageous process which obviates the use of expensive jacketed reactors, application of elevated temperature conditions, residue generation, less reaction time, formation of by- products such as benzonitrile polymer and tetraphenylmethane. OBJECTIVE OF THE INVENTION: Some of the objects of the present invention are described herein below: It is an object of the present invention to ameliorate one or more problems of the prior art or to at least provide a useful alternative. An object of the present invention is to provide a simple process for the preparation of benzonitrile compounds of Formula (I) from the corresponding benzotrichloride compounds of Formula (II). Another object of the present invention is to provide a process for the preparation of benzonitrile compounds of Formula (I) from corresponding benzotrichloride compounds of Formula (II) which at least partially reduces the energy requirement. Yet another object of the present invention is to provide a process for the preparation of benzonitrile compounds of Formula (I) from corresponding benzotrichloride compounds of Formula (II) which requires comparatively lower or milder temperature conditions. Yet another object of the present invention is to provide a process for the preparation of high purity benzonitrile compounds of Formula (I) from corresponding benzotrichloride compounds of Formula (II) which at least partially obviates the polymerization and the formation of undesired by-products. Yet another object of the present invention is to provide a process for the preparation of benzonitrile compounds of Formula (I) from corresponding benzotrichloride compounds of Formula (II) which at least partially obviates the solid waste generation and hence is more environmentally friendly. Yet another object of the present invention is to provide a process for the preparation of benzonitrile compounds of Formula (I) from corresponding benzotrichloride compounds of Formula (II), wherein the reaction time is at least partially reduced. Other objects and advantages of the present invention will be more apparent from the following description which is not intended to limit the scope of the present invention. SUMMARY OF THE INVENTION: In one aspect, the present invention provides a process for the preparation of benzonitrile compound of Formula (I); wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; comprising the step of nitrilation of a benzotrichloride compound of Formula (II); wherein, R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (I). In an exemplary embodiment, the present invention provides a process for the preparation of benzonitrile compound of Formula (III); Formula (III) wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; comprising the step of nitrilation of a benzotrichloride compound of Formula (IV); Formula (IV) wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (IV). In second aspect, the present invention provides a process for the preparation of benzonitrile compound of Formula (I); wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; comprising the step of nitrilation of a benzotrichloride compound of Formula (II); wherein, R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (I). In an exemplary embodiment, the present invention provides a process for the preparation of benzonitrile compound of Formula (III); Formula (III) wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; comprising the step of nitrilation of a benzotrichloride compound of Formula (IV); Formula (IV) wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (IV). It is unexpectedly surprising for the inventor that the amount of the initiator and the catalyst plays an important role in obviating the use of expensive jacketed reactors, application of elevated temperature conditions and at least partially reducing or obviating the formation of by-products such as benzonitrile polymer and tetraphenylmethane while resulting in the improved purity of the product. DESCRIPTION OF THE INVENTION: 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. 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 disclosure to achieve one or more of the desired objects or results. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher / lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art. In case of conflict, the present document, including definitions will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present invention. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting. The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The term “halogen” includes fluorine or chlorine. The singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not. In view of the above defined objectives, the present invention provides a process for the preparation of benzonitrile compounds of Formula (I) wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; comprising the step of nitrilating benzotrichloride compound of Formula (II); wherein, R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable catalyst selected from para-toluene sulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst, ion exchange resin, sulfuric acid, phosphoric acid, water and combinations thereof, optionally in the presence of a suitable initiator and optionally in the presence of a suitable inert solvent at a temperature in the range of 150-200 °C to afford the benzonitrile compound of Formula (I). In first aspect of the present invention, the process for the preparation of benzonitrile compound of Formula (I) by nitrilating benzotrichloride compound of Formula (II) which is depicted in scheme 1 below: Scheme: 1 wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (I). Non limiting examples of the compound of Formula (I) in accordance with the first aspect include ortho-chlorobenzonitrile, para-chlorobenzonitrile, meta-chlorobenzonitrile, ortho- fluorobenzonitrile, para-fluorobenzonitrile, meta-fluorobenzonitrile, 2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4- dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3-difluorobenzonitrile, 2,4- difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4- difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3-benzenedicarbonitrile, 1,4- benzenedicarbonitrile and 2-chloro-6-fluoro benzonitrile. Preferably, the compound of Formula (I) in accordance with the first aspect is selected from the group consisting of ortho-chlorobenzonitrile, para-chlorobenzonitrile, 2,4- dichlorobenzonitrile, 1,3-benzenedicarbonitrile and 2-chloro-6-fluoro benzonitrile. Non limiting examples of the compound of Formula (II) in accordance with the first aspect include ortho-chlorobenzotrichloride, para-chlorobenzotrichloride, meta- chlorobenzotrichloride, ortho-fluorobenzotrichloride, para-fluorobenzotrichloride, meta- fluorobenzotrichloride, 2,3-dichlorobenzotrichloride, 2,4-dichlorobenzotrichloride, 2,5- dichlorobenzotrichloride, 2,6-dichlorobenzotrichloride, 3,4-dichlorobenzotrichloride, 3,5- dichlorobenzotrichloride, 2,3-difluorobenzotrichloride, 2,4-difluorobenzotrichloride, 2,5- difluorobenzotrichloride, 2,6-difluorobenzotrichloride, 3,4-difluorobenzotrichloride, 3,5- difluorobenzotrichloride, 1,3-bis(trichloromethyl)benzene, 1,4-bis(trichloromethyl)benzene and 2-chloro-6-fluoro benzotrichloride. Preferably, the compound of Formula (II) in accordance with the first aspect is selected from the group consisting of ortho-chlorobenzotrichloride, para-chlorobenzotrichloride, 2,4- dichlorobenzotrichloride, 1,3-bis(trichloromethyl)benzene and 2-chloro-6-fluoro benzotrichloride. Typically, the suitable ammonium salt in accordance with the first aspect is selected from ammonium chloride or ammonium bromide. Non-limiting examples of the catalyst suitable for the conversion as shown in scheme 1 in accordance with the first aspect include para-toluene sulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst, ion exchange resin (e.g., indion®), sulfuric acid, phosphoric acid, water or combinations thereof. By operating in accordance with the first aspect of the present invention, the time required for completing or nearly completing the reaction is within the range from 8 hrs to 30 hrs. More preferably, the time required for completing the reaction is in the range of 12 to 28 hrs. By operating in accordance with the first aspect of the present invention, the said reaction can be carried out at a pressure in the range of 1 to 10 kg / cm2. More preferably, the pressure of said reaction can be in the range of 1 to 5 kg / cm2. By operating in accordance with the first aspect of the present invention, the reaction time can be reduced from 12 to 28 hrs to 10 to 15 hrs when the pressure of said reaction is in the range of 1 to 5 kg / cm2. Typically, the amount of the catalyst ranges between 0.1 to 1.0 wt.% with respect to the compound of Formula (II). Non-limiting examples of the inert solvent suitable for the conversion as shown in Scheme 1 in accordance with the first aspect include the compound of Formula (I), xylene, monochlorobenzene, dichlorobenzenes, sulfolane, ortho-chlorobenzonitrile, toluene or combination thereof. In an exemplary embodiment of the first aspect, the present invention provides a process for the preparation of benzonitrile compound of Formula (IV) by nitrilating benzotrichloride compound of Formula (III) which is depicted in Scheme 2 below: Formula (III) Formula (IV) Scheme: 2 wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; using a suitable ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (IV). Typically, the suitable catalyst, inert solvent, temperature range, pressure conditions and time required for the conversion as shown in Scheme 2 is the same as described for the first aspect. In a specific exemplary embodiment of the first aspect, the process for the preparation of ortho- chlorobenzonitrile from ortho-chlorobenzotrichloride as disclosed in the present invention is depicted in Scheme 3 below: Scheme: 3 The ortho-chlorobenzotrichloride is nitrilated using ammonium salt in the presence of a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford ortho-chlorobenzonitrile. Typically, the suitable catalyst, inert solvent, temperature range, pressure conditions and time required for the conversion as shown in Scheme 3 is the same as described for the first aspect. In second aspect of the present invention, the process for the preparation of benzonitrile compound of Formula (I) by nitrilating benzotrichloride compound of Formula (II) which is depicted in scheme 1 below: Scheme: 1 wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (I). Non limiting examples of the compound of Formula (I) in accordance with the second aspect include ortho-chlorobenzonitrile, para-chlorobenzonitrile, meta-chlorobenzonitrile, ortho- fluorobenzonitrile, para-fluorobenzonitrile, meta-fluorobenzonitrile, 2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4- dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3-difluorobenzonitrile, 2,4- difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4- difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3-benzenedicarbonitrile, 1,4- benzenedicarbonitrile and 2-chloro-6-fluoro benzonitrile. Preferably, the compound of Formula (I) in accordance with the second aspect is selected from the group consisting of ortho-chlorobenzonitrile, para-chlorobenzonitrile, 2,4- dichlorobenzonitrile, 1,3-benzenedicarbonitrile and 2-chloro-6-fluoro benzonitrile. Non limiting examples of the compound of Formula (II) in accordance with the second aspect include ortho-chlorobenzotrichloride, para-chlorobenzotrichloride, meta- chlorobenzotrichloride, ortho-fluorobenzotrichloride, para-fluorobenzotrichloride, meta- fluorobenzotrichloride, 2,3-dichlorobenzotrichloride, 2,4-dichlorobenzotrichloride, 2,5- dichlorobenzotrichloride, 2,6-dichlorobenzotrichloride, 3,4-dichlorobenzotrichloride, 3,5- dichlorobenzotrichloride, 2,3-difluorobenzotrichloride, 2,4-difluorobenzotrichloride, 2,5- difluorobenzotrichloride, 2,6-difluorobenzotrichloride, 3,4-difluorobenzotrichloride, 3,5- difluorobenzotrichloride, 1,3-bis(trichloromethyl)benzene, 1,4-bis(trichloromethyl)benzene and 2-chloro-6-fluoro benzotrichloride. Preferably, the compound of Formula (II) in accordance with the second aspect is selected from the group consisting of ortho-chlorobenzotrichloride, para-chlorobenzotrichloride, 2,4- dichlorobenzotrichloride, 1,3-bis(trichloromethyl)benzene and 2-chloro-6-fluoro benzotrichloride. Typically, the suitable ammonium salt in accordance with the second aspect is selected from ammonium chloride or ammonium bromide. Typically, the initiator suitable for the conversion as shown in Scheme 1 in accordance with the second aspect of the present invention is represented by Formula (V); wherein, R6and R7are independently selected from the consisting of hydrogen, X and -CO-R5; R5are independently selected from the consisting of -OH, -NH2 and -Cl; provided that, R6and R7may not be -CO-R5at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3. Non limiting examples of the initiator of Formula (V) in accordance with the second aspect include benzoic acids such as ortho-chlorobenzoic acid, para-chlorobenzoic acid, meta- chlorobenzoic acid, ortho-fluorobenzoic acid, para-fluorobenzoic acid, meta-fluorobenzoic acid; halogen substituted or unsubstituted 1,4-benzenedicarboxylic acid, halogen substituted or unsubstituted 1,3-benzenedicarboxylic acid; benzoyl chlorides such as ortho-chlorobenzoyl chloride, para-chlorobenzoyl chloride, meta-chlorobenzoyl chloride, ortho-fluorobenzoyl chloride, para-fluorobenzoyl chloride, meta-fluorobenzoyl chloride; halogen substituted or unsubstituted 1,4-benzenedicarbonyl dichloride, halogen substituted or unsubstituted 1,3- benzenedicarbonyl dichloride; benzamides such as ortho-chlorobenzamide, para- chlorobenzamide, meta-chlorobenzamide, ortho-fluorobenzamide, para-fluorobenzamide, meta-fluorobenzamide, halogen substituted or unsubstituted 1,4-benzenedicarboxamide, halogen substituted or unsubstituted 1,3-benzenedicarboxamide or combinations thereof. Non-limiting examples of the catalyst suitable for the conversion as shown in Scheme 1 in accordance with the second aspect include para-toluene sulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst, ion exchange resin (e.g., indion®), sulfuric acid, phosphoric acid, water and combinations thereof. By operating in accordance with the second aspect of the present invention, the time required for completing or nearly completing the reaction is within the range from 8 hrs to 30 hrs. More preferably, the time required for the completion of the reaction is in the range of 12 to 28 hrs. By operating in accordance with the second aspect of the present invention, the pressure of said reaction is in the range of 1 to 10 kg / cm2. More preferably, the pressure of said reaction is in the range of 1 to 5 kg / cm2. By operating in accordance with the second aspect of the present invention, the pressure of said reaction is in the range of 1 to 5 kg / cm2wherein the reaction time is reduced from 12 to 28 hrs to 10 to 15 hrs. Typically, the amount of initiator ranges between 1.0 to 10.0 wt.% with respect to the compound of Formula (II). Typically, the amount of the catalyst ranges between 0.1 to 1.0 wt.% with respect to the compound of Formula (II). Non-limiting examples of the inert solvent suitable for the conversion as shown in Scheme I in accordance with the second aspect include the compound of Formula (I), xylene, monochlorobenzene, dichlorobenzenes, sulfolane, ortho-chlorobenzonitrile, toluene and combinations thereof. In an exemplary embodiment of the second aspect, the present invention provides a process for the preparation of benzonitrile compound of Formula (IV) by nitrilating benzotrichloride compound of Formula (III) which is depicted in Scheme 2 below: Formula (III) Formula (IV) Scheme: 2 wherein, X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 5; using a suitable ammonium salt in the presence of a suitable initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford the benzonitrile compound of Formula (IV). Typically, the suitable catalyst, inert solvent, temperature range, pressure conditions and time required for the conversion as shown in Scheme 2 is the same as described for the second aspect. In a specific exemplary embodiment of the second aspect, the process for the preparation of ortho-chlorobenzonitrile from ortho-chlorobenzotrichloride as disclosed in the present invention is depicted in scheme 3 below: Scheme: 3 The ortho-chlorobenzotrichloride is nitrilated using ammonium salt in the presence of ortho- chlorobenzoic acid as an initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford ortho-chlorobenzonitrile. Typically, the suitable catalyst, inert solvent, temperature range, pressure conditions and time required for the conversion as shown in Scheme 3 is the same as described for the second aspect. In an alternative specific exemplary embodiment of the second aspect ortho- chlorobenzotrichloride is nitrilated using ammonium salt in the presence of ortho- chlorobenzoyl chloride as an initiator, a suitable catalyst and optionally in the presence of a suitable inert solvent at a temperature in the range of 150 to 200 °C to afford ortho- chlorobenzonitrile. In accordance with the present invention, the compound of Formula (I) is obtained in the yield ranging from 70 to 95%. Preferably, the compound of Formula (I) is obtained in the yield ranging from 85 to 95%. By operating in accordance with the process of the present invention, practically complete conversion of compounds of Formula (II) is achieved with high selectivity. The benzonitrile obtained in accordance with the present invention can be easily separated from the reaction mixture, and in particular from the catalyst and the excess of the ammonium salt, by known techniques, such as distillation, separation and solvent treatment. In particular, the benzonitrile can be directly distilled off from the reaction mixture, or it can be extracted by dissolution in a suitable organic solvent. In any case, the catalyst, initiator or the ammonium salt can be easily recovered and recycled to a subsequent reaction cycle, a feature of which is desirable and the intended outcome of the present invention. Various features and embodiments of the present invention are illustrated in the following representative examples, which are intended to be illustrative and non-limiting. Examples: Example 1: Preparation of ortho-chlorobenzonitrile To a reactor 195 g of ortho-chlorobenzotrichloride, 10 g of ortho-chlorobenzoyl chloride, 0.5 g of p-toluene sulphonic acid and 55.8 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho- chlorobenzotrichloride reached <0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 86.0%; Purity: >99.0 %). Example 2: Preparation of ortho-chlorobenzonitrile To a reactor 20 g of ortho-chlorobenzotrichloride, 50 g of ortho-chlorobenzonitrile was added at room temperature and the reaction mass was heated. To this reaction mixture, 1.4 g of aqueous sulfuric acid solution was added for 20 minutes followed by the addition of 55.8 g of ammonium chloride. The reaction mass was heated to 170-175 °C. Further, to this reaction mixture, 190 g of ortho-chlorobenzotrichloride was added by dropwise addition at 170-175oC for 16 hrs. After completion of the reaction, when the content of ortho-chlorobenzotrichloride <0.2%, the reaction mass was cooled to 110 °C. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 90.26 %, Purity: > 99.5 %). Example 3: Preparation of ortho-chlorobenzonitrile To a reactor 195 g of ortho-chlorobenzotrichloride, 10 g of ortho-chlorobenzoyl chloride, 0.4 g of phosphoric acid and 55.8 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho-chlorobenzotrichloride reached <0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 85.0%; Purity: >99.0 %). Example 4: Preparation of ortho-chlorobenzonitrile To a reactor 100 gm of ortho-chlorobenzotrichloride, 2.0 g of ortho-chlorobenzoic acid, 0.5 g of amberlyst and 28.2 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 70%, Purity: > 99 %). Example 5: Preparation of ortho-chlorobenzonitrile To a reactor 100 g of ortho-chlorobenzotrichloride, 2.0 g of ortho-chlorobenzoic acid, 0.2 g of sulfuric acid and 28.2 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho-chlorobenzotrichloride < 0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 90.0%; Purity: >99.5 %). Example 6: Preparation of ortho-chlorobenzonitrile To a reactor 195 g of ortho-chlorobenzotrichloride, 10 g of ortho-chlorobenzoyl chloride, 0.4 g of sulfuric acid and 55.8 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho-chlorobenzotrichloride <0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 94.0%; Purity: >99.5 %). Example 7: Preparation of ortho-chlorobenzonitrile in the presence of OCBN as solvent To a reactor 100 g of ortho-chlorobenzotrichloride, 2.0 g of ortho-chlorobenzoic acid, 25 g of ortho-chlorobenzonitrile, 0.2 g of sulfuric acid and 28.2 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho- chlorobenzotrichloride <0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 90.0%; Purity: >99.5 %). Example 8: Preparation of ortho-chlorobenzonitrile in the presence of sulfolane as solvent To a reactor 100 g of ortho-chlorobenzotrichloride, 2.0 g of ortho-chlorobenzoic acid, 0.2 g of sulfuric acid, 25 g of sulfolane and 28.2 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho- chlorobenzotrichloride <0.2%. The crude ortho-chlorobenzonitrile thus obtained was purified by distillation (Yield: 89.0%; Purity: >99.5 %). Example 9: Preparation of ortho-chlorobenzonitrile To a reactor 200 g of ortho-chlorobenzotrichloride, 0.4 g of sulfuric acid was added at room temperature and the reaction mass was heated to 150-155 °C. To this reaction mixture 1.0 g water was added at 155-160oC for 20 minutes followed by the addition of 55.8 g of ammonium chloride. The reaction mass was heated to 180-185 °C. The resulting reaction mass was heated at 180-185oC and for 25 hrs. After completion of the reaction when the content of ortho- chlorobenzotrichloride <0.2%, the reaction mass was cooled to 110 °C. The crude ortho- chlorobenzonitrile thus obtained was purified by distillation (Yield: 89.5 %; Purity: >99.5 %). Example 10: Preparation of para-chlorobenzonitrile To a reactor 195 g of para-chlorobenzotrichloride, 10 g of para-chlorobenzoyl chloride, 0.2 g of sulfuric acid and 55.8 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of ortho-chlorobenzotrichloride reached <0.2%. The crude para-chlorobenzonitrile thus obtained was purified by distillation (Yield: 94.0%; Purity: >99.5 %). Example 11: Preparation of 2,4-dichlorobenzonitrile To a reactor 195 g of 2,4-dichlorobenzotrichloride, 10 g of 2,4-dichlorobenzoyl chloride, 0.4 g of sulfuric acid and 48.6 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 190-195 °C and the reaction mixture was maintained for 26 hrs. The reaction mass was cooled to 110 °C when the content of ortho-chlorobenzotrichloride reached <0.2%. The crude 2,4-dichlorobenzonitrile thus obtained was purified by distillation (Yield: 90.0%; Purity: >99.0%). Example 12: Preparation of ortho-chlorobenzonitrile To a reactor 195 g of ortho-chlorobenzotrichloride, 10 g of ortho-chlorobenzoyl chloride, 0.4 g of sulfuric acid and 55.8 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 12 hrs at 3 kg / cm2pressure. The reaction mass was cooled to 110 °C and pressure was released when the content of ortho-chlorobenzotrichloride reached <0.2%. The crude ortho- chlorobenzonitrile thus obtained was purified by distillation (Yield: 93.0%; Purity: >99.5 %). Example 13: Preparation of 1,3-benzenedicarbonitrile To a reactor 195 g of 1,3-bis(trichloromethyl)benzene, 15 g of 1,3-benzene dicarbonyl dichloride, 0.4 g of sulfuric acid and 74 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 190-195 °C and the reaction mixture was maintained for 25 hrs. The reaction mass was cooled to 110 °C when the content of 1,3- bis(trichloromethyl)benzene reached <0.2%. The crude 1,3-benzenedicarbonitrile thus obtained was purified by distillation (Yield: 90.0%; Purity: >99.0 %). Example 14: Preparation of 2-chloro-6-fluoro benzonitrile To a reactor 195 g of 2-chloro-6-fluoro benzotrichloride, 10 g of 2-chloro-6-fluoro benzoyl chloride, 0.4 g of sulfuric acid and 50.51 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 190-195 °C and the reaction mixture was maintained for 28 hrs. The reaction mass was cooled to 100 °C when the content of 2-chloro- 6-fluoro benzotrichloride reached <0.2%. The crude 2-chloro-6-fluoro benzonitrile thus obtained was purified by distillation (Yield: 89.0%; Purity: >99.0%). Comparative Example 1: Preparation of ortho-chlorobenzonitrile using metal salts as catalyst To a reactor 100 g of ortho-chlorobenzotrichloride, 2.0 g of ortho-chlorobenzoic acid, ZnCl2 / CuO catalyst and 28.2 g of ammonium chloride were charged at room temperature. The reaction mass was heated to 180-185 °C and the reaction mixture was maintained for 25 hrs. It was observed that the process for preparation of ortho-chlorobenzonitrile using metal salts as catalyst was sluggish and therefore found that metal catalysts are not suitable in the absence of sulfuric acid in the process for preparation of ortho-chlorobenzonitrile. The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to a person skilled in the art, the invention should be construed to include everything within the scope of the disclosure. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the 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. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. The description of the specific embodiments will 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. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the invention herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Claims

WE CLAIM: 1) A process for the preparation of benzonitrile compounds of Formula (I)wherein, R1and R2are independently selected from the consisting of hydrogen, X and cyano; provided that, R1and R2may not be cyano at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; comprising the step of nitrilating benzotrichloride compound of Formula (II);wherein, R3and R4are independently selected from the consisting of hydrogen, X and trichloromethyl; provided that, R3and R4may not be trichloromethyl at the same time; X is a halogen selected from fluorine and chlorine; and n is an integer ranging from 1 to 3; using a suitable ammonium salt in the presence of a suitable catalyst selected from para-toluene sulfonic acid, methanesulfonic acid, phosphonic acid, amberlyst, ion exchange resin, sulfuric acid, phosphoric acid, water and combinations thereof, optionally in the presence of a suitable initiator and optionally in the presence of a suitable inert solvent at a temperature in the range of 150-200 °C to afford the benzonitrile compound of Formula (I).2) The process as claimed in claim 1, wherein a) said suitable ammonium salt is selected from the group consisting of ammonium chloride or ammonium bromide; and b) said suitable inert solvent is selected from the group consisting of the compound of Formula (I), xylene, monochlorobenzene, dichlorobenzenes, sulfolane, ortho-chlorobenzonitrile, toluene and combinations thereof. 3) The process as claimed in claim 1, wherein a) the amount of the catalyst is in the range of 0.1 to 1.0 wt.% with respect to the compound of Formula (II); and b) the amount of initiator is in the range of 1.0 to 10.0 wt.% with respect to the compound of Formula (II). 4) The process as claimed in claim 1, wherein the said reaction is carried out at a pressure in the range of 1 to 10 kg / cm2and the reaction time is in the range of 8 to 15 hrs. 5) The process as claimed in claim 1, wherein the said reaction is carried out at a pressure in the range of 1 to 5 kg / cm2and the reaction time is in the range of 10 to 15 hrs. 6) The process as claimed in claim 1, wherein the yield of benzonitrile compound of Formula (I) is in the range from 70 to 95%. 7) The process as claimed in claim 1, wherein the said initiator is represented by compound of Formula (V);wherein, R6and R7are independently selected from the consisting of hydrogen, X and -CO-R5; R5are independently selected from the consisting of -OH, -NH2 and -Cl; provided that, R6and R7may not be -CO-R5at the same time; X is a halogen selected from fluorine and chlorine; andn is an integer ranging from 1 to 3. 8) The process as claimed in claim 7, wherein said suitable initiator of Formula (V) is selected from the group consisting of benzoic acids such as ortho-chlorobenzoic acid, para-chlorobenzoic acid, meta-chlorobenzoic acid, ortho-fluorobenzoic acid, para- fluorobenzoic acid, meta-fluorobenzoic acid, halogen (un)substituted 1,4- benzenedicarboxylic acid, halogen (un)substituted 1,3-benzenedicarboxylic acid; benzoyl chlorides such as ortho-chlorobenzoyl chloride, para-chlorobenzoyl chloride, meta-chlorobenzoyl chloride, ortho-fluorobenzoyl chloride, para-fluorobenzoyl chloride, meta-fluorobenzoyl chloride, halogen (un)substituted 1,4-benzenedicarbonyl dichloride, halogen (un)substituted 1,3-benzenedicarbonyl dichloride; benzamides such as ortho-chlorobenzamide, para-chlorobenzamide, meta-chlorobenzamide, ortho- fluorobenzamide, para-fluorobenzamide, meta-fluorobenzamide, halogen (un)substituted 1,4-benzenedicarboxamide, halogen (un)substituted 1,3- benzenedicarboxamide and combinations thereof. 9) The process as claimed in claim 1, wherein said compound of Formula (I) is selected from ortho-chlorobenzonitrile, para-chlorobenzonitrile, meta-chlorobenzonitrile, ortho-fluorobenzonitrile, para-fluorobenzonitrile, meta-fluorobenzonitrile, 2,3- dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6- dichlorobenzonitrile, 3,4-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,3- difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6- difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile, 1,3- benzenedicarbonitrile, 1,4-benzenedicarbonitrile and 2-chloro-6-fluoro benzonitrile. 10) The process as claimed in claim 1, wherein said compound of Formula (II) is selected from ortho-chlorobenzotrichloride, para-chlorobenzotrichloride, meta- chlorobenzotrichloride, ortho-fluorobenzotrichloride, para-fluorobenzotrichloride, meta-fluorobenzotrichloride, 2,3-dichlorobenzotrichloride, 2,4- dichlorobenzotrichloride, 2,5-dichlorobenzotrichloride, 2,6-dichlorobenzotrichloride, 3,4-dichlorobenzotrichloride, 3,5-dichlorobenzotrichloride, 2,3- difluorobenzotrichloride, 2,4-difluorobenzotrichloride, 2,5-difluorobenzotrichloride, 2,6-difluorobenzotrichloride, 3,4-difluorobenzotrichloride, 3,5- difluorobenzotrichloride, 1,3-bis(trichloromethyl)benzene, 1,4- bis(trichloromethyl)benzene and 2-chloro-6-fluoro benzotrichloride.

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