Claims:1. A process for preparing a crystalline form of a 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride, comprising:
addition of a 1-[-(2-chlorophenyl) (methylamine) methyl] cyclopentanol hydrochloride to a first organic solvent to obtain a reaction mass;
heating the reaction mass at a temperature range of 160oC to 165oC for a predetermined time period to obtain a slurry reaction mass, wherein the obtained slurry reaction mass is dissolved and a product is isolated from the reaction mass;
cooling the isolated product at a temperature range of 20oC to 25oC;
filtering and washing the isolated product with a second organic solvent;
drying the isolated product at a temperature range of 70oC to 80oC up to a constant weight to obtain the crystalline form of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride; and
processing the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to obtain one or more crystalline forms.
2. The process as claimed in claim 1, wherein the first organic solvent is ortho dichlorobenzene in the range of 3 to 3.5 volume.

3. The process as claimed in claim 1, wherein the predetermined time period is 30mins.

4. The process as claimed in claim 1, wherein the second organic solvent is acetone in the range of 0.3 to 3.5 volume.

5. The process as claimed in claim 1, wherein the one or more polymorphs of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride are in the form of a small crystals, a sugar like crystals, a rock candy like crystals and a needle like crystals.

6. The process as claimed in claim 1, wherein processing the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to obtain one or more crystalline forms comprises of:
adding the obtained 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to water;
heating the reaction mass at a temperature range of 40oC to 50oC followed by activated carbon treatment;
cooling the reaction mass at a temperature range of 10oC to 15oC;
filtering the reaction mass and adjusting the pH to be in the range of 9.5 to 10 by addition of liquid ammonia and the reaction mass was continuously stirred for at least 30minutes at a temperature range of 10oC to 15oC; and
filtering the ketamine base and washed with water to obtain a wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone.

7. The process as claimed in claim 6, wherein the process of preparation of the small crystal like polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of:
adding of wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% aqueous isopropyl alcohol to obtain a reaction mass;
adjusting the moisture of the reaction mass to 8.0% to 10%;
heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment;
cooling the carbon treated filtrate at a temperature of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid solution;
distillation of the isopropyl alcohol from the reaction mass;
cooling the reaction mass at a temperature in the range of 5oC to 10oC;
filtering the reaction mass to isolate the product; and
drying the isolated product at a temperature in the range of 80oC to 85oC to obtain small crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride.

8. The process as claimed in claim 6, wherein the process of preparation of sugar like crystal form of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of:
adding the wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% an aqueous isopropyl alcohol to obtain a reaction mass;
adjusting the moisture of the reaction mass to 8.0% to 10.0%;
heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment;
cooling the carbon treated reaction mass at a temperature in the range of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid;
heating the reaction mass at a temperature of 78oC and adding of demineralized water to dissolve the solids (water content 8% to 15%) followed by distillation of isopropyl alcohol to obtain the slurry at the same temperature;
cooling the reaction mass at a temperature in the range of 25oC to 30oC;
filtering to isolate the product and followed by IPA washing at a lower temperature;
drying the isolated product at a temperature in the range of 80oC to 85oC to obtain sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

9. The process as claimed in claim 6, wherein the process of preparation of rock candy crystal like polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of:
adding of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to methanol;
heating the reaction mass at a temperature in the range of 60oC to 65oC;
cooling the reaction mass overnight and removing rock candy like crystals;
concentrating the mother liquor at a temperature of 45oC under vacuum till occurrence of turbidity;
heating the reaction mass at a temperature of 60oC to 65oC to get clear reaction mass;
cooling the reaction mass overnight without any disturbance;
drying, milling and sieving to obtain rock candy like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

10. The process as claimed in claim 6, wherein the process of preparation of needle like crystal polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of:
a) adding of the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to a demineralized water (1.5 volume to 2.0 volume) at a room temperature;
b) heating the reaction mass at a temperature in the range of 60oC to 75oC for achieving complete dissolution;
c) cooling the reaction mass at a temperature in the range of 55oC for 24 to 26 hours;
d) adding water to a Jacket at regular intervals to cool the contents at a temperature in the range of 30oC to 40oC for over 10 to 18 hours;
e) filtering the isolated needle type crystal by washing with isopropyl alcohol;
f) collecting water from the mother liquor and repeating the steps (a) to (e) for seven times; and
g) drying and sieving the needle like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride;

Dated this 31st day of March 2021

Signature

Harish Naidu
Patent Agent (IN/PA-2896)
Agent for the Applicant
, Description:FIELD OF INVENTION
[0001] Embodiment of the present disclosure relates to a different crystalline forms of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride and method of preparing the same.

BACKGROUND OF THE INVENTION
[0002] Ketamine hydrochloride is a nonbarbiturate anaesthetic used for diagnostic and surgical procedures, with a wide range of effects in humans such as confusion, hallucinations, light-headedness, weak breathing,

[0003] US 3254124 discloses the thermal rearrangement of 1-hydroxycyclopentyl-(o-Chlorophenyl)-Ketone N-Methylamine at reflux (boiling point about 190oC) for two hours in decaline.

[0004] US20140275276A1 discloses an aqueous formulation of S-Ketamine Hydrochloride, preferably for nasal administration and that the formulation does not contain an antimicrobial preservative.

[0005] The presently available process are costlier and less-efficient in consumption of utilities to obtain ketamine hydrochloride. Also, the processes in the state-of-art cannot synthesize different types of crystals required for different formulations. Therefore, there is a need for an alternative low-cost and effective process for obtaining new crystalline form of ketamine hydrochloride synthesis.

SUMMARY OF THE INVENTION

[0006] In accordance with an embodiment of the present invention, a process for preparing a crystalline form of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride, comprising addition of 1-[-(2-chlorophenyl) (methylamine) methyl] cyclopentanol hydrochloride to a first organic solvent to obtain a reaction mass, heating the reaction mass in a temperature range of 160oC to 165oC for a predetermined time period to obtain a slurry reaction mass, wherein the obtained slurry reaction mass is dissolved and a crystalline form is isolated from the reaction mass, cooling the isolated crystalline form in the temperature range of 20oC to 250C, filtering and washing the isolated crystalline form with a second organic solvent. and drying the isolated crystalline form at 70oC to 80oC up to a constant weight to obtain 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0007] In accordance with an embodiment of the present invention, wherein the first organic solvent is ortho dichlorobenzene in the range of 3 to 3.5 volume.

[0008] In accordance with an embodiment of the present invention, wherein the predetermined time period is 30 mins.

[0009] In accordance with an embodiment of the present invention, wherein the second organic solvent is acetone in the range of 0.3 to 0.5 volume.

[0010] In accordance with an embodiment of the present invention, wherein the total yield of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride is 88%.

[0011] In accordance with an embodiment of the present invention, wherein the one or more polymorphs of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride are in the form of a small crystals, a sugar like crystals, a rock candy like crystals and a needle like crystals.
[0012] In accordance with an embodiment of the present invention, wherein processing the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to obtain one or more polymorphs comprises of adding the obtained 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to water, heating the reaction mass at a temperature range of 40oC to 50oC followed by activated carbon treatment, filtering the reaction mass, followed by cooling temperature range of 10oC to 15oC, and adjusting the pH to be in the range of 9.5 to 10 by addition of liquid ammonia and the reaction mass was continuously stirred for at least 30 minutes at a temperature range of 10oC to 15oC; and filtering the ketamine base and washed with water to obtain a wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone.

[0013] In accordance to an embodiment of the present invention, wherein the process of preparation of the small crystal like polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding of wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% aqueous isopropyl alcohol to obtain a reaction mass, adjusting the moisture of the reaction mass to 8.0% to 10%, heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment, cooling the carbon treated filtrate at a temperature of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid solution, distillation of the isopropyl alcohol from the reaction mass, cooling the reaction mass at a temperature in the range of 5oC to 10oC, filtering the reaction mass to isolate the product and drying the isolated product at a temperature in the range of 80oC to 85oC to obtain small crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0014] In accordance to an embodiment of the present invention, wherein the process of preparation of sugar like crystal polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding the wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% an aqueous isopropyl alcohol to obtain a reaction mass, adjusting the moisture of the reaction mass to 8.0% to 10.0%, heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment, cooling the carbon treated reaction mass at a temperature in the range of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid, heating the reaction mass at a temperature of 78oC and adding of demineralized water to dissolve the solids followed by distillation of isopropyl alcohol to obtain the slurry at the same temperature, cooling the reaction mass at a temperature in the range of 25oC to 30oC, filtering to isolate the product and followed by IPA washing at a lower temperature, drying the isolated product at a temperature in the range of 80oC to 85oC to obtain sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0015] In accordance to an embodiment of the present invention, wherein the process of preparation of rock candy crystal like polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to methanol, heating the reaction mass at a temperature in the range of 60oC to 65oC, cooling the reaction mass overnight and removing rock candy like crystals, concentrating the mother liquor at a temperature of 45oC under vacuum till occurrence of turbidity, heating the reaction mass at a temperature of 60oC to 65oC to get clear reaction mass, cooling the reaction mass overnight without any disturbance and drying, milling and sieving to obtain rock candy like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0016] In accordance with an embodiment of the present invention, wherein the process of preparation of needle like crystal polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding of the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to a demineralized water at a room temperature, heating the reaction mass at a temperature in the range of 60oC to 75oC for achieving complete dissolution, cooling the reaction mass at a temperature in the range of 55oC for 24 to 26 hours, adding water to the reaction mass at regular intervals to cool the contents at a temperature in the range of 30oC to 40oC for over 10 to 18 hours, filtering the isolated needle type crystal by washing with isopropyl alcohol, collecting water from the mother liquor and repeating the previous steps for seven times and drying and sieving the needle like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0017] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:

[0019] FIG. 1 illustrates a flow chart depicting process for preparing a crystalline form of a 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride;

[0020] FIG. 2 shows small crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure;

[0021] FIG. 3 shows sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride in accordance with an embodiment of the present disclosure;

[0022] FIG. 4 shows rock candy like crystals 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure;

[0023] FIG. 5 shows needle like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure;

[0024] Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
DETAILED DESCRIPTION OF THE INVENTION
[0025] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

[0026] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The examples provided herein are only illustrative and not intended to be limiting.

[0028] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

[0029] As used herein, the term “ketamine hydrochloride” refers to a prescription medicine used as a sedative for diagnostic and surgical procedures. It is a nonbarbiturate anaesthetic chemically as designated dl 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0030] FIG. 1 illustrates a flow chart depicting process for preparing a crystalline form of a 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride. According to an embodiment of the present invention, thermal rearrangement of 1-hydroxycyclopentyl-(0-chlorophenyl)-ketone-N-methylimine hydrochloride by using ortho dichlorobenzene to obtain 2-(2-chlorophenyl)-2-(methylamino)cyclohexanone hydrochloride.

[0031] According to an embodiment of the present invention, at step 102, it involves addition of a 1-[-(2-chlorophenyl) (methylamine) methyl] cyclopentanol hydrochloride to a first organic solvent to obtain a reaction mass, wherein the first organic solvent is ortho dichlorobenzene in the range of 3 to 3.5 volume.

[0032] At step 104, it involves heating the reaction mass at a temperature range of 160oC to 165oC for a predetermined time period to obtain a slurry reaction mass, wherein the obtained slurry reaction mass is dissolved and a product is isolated from the reaction mass, wherein the predetermined time period is 30mins.

[0033] At step 106, involves cooling the isolated product at a temperature range of 20oC to 25oC.

[0034] At step 108, filtering and washing the isolated product with a second organic solvent, wherein the second organic solvent is acetone in range of 0.3 to 0.5 volume.

[0035] At step 110, drying the isolated product at a temperature range of 70oC to 80oC up to a constant weight to obtain the crystalline form of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0036] At step 112, processing the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to obtain one or more polymorphs, wherein the one or more polymorphs of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride are in the form of a small crystals, a sugar like crystals, a rock candy like crystals and a needle like crystals.

EXAMPLE 1
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride

[0037] In a reactor, 420 kg 1-[-(2-chlorophenyl) (methylamino) methyl] cyclopentanol hydrochloride was added to 1260 litre of Ortho dichlorobenzene. The reaction mass is heated to 160oC to 165oC for 30 minutes. The slurry reaction mass was dissolved & then got isolated from the reaction. Cooling was applied to 20oC to 25oC followed by filtration & 150 litre Acetone wash. After drying at 70oC to 80oC up to a constant weight, 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride was obtained.

EXAMPLE-2
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone
[0038] In a reactor, 300 kg of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride was added to 1800 litre of process water. The reaction mass was hated to a temperature in the range of 40oC to 50oC followed by 5 kg of Activated carbon treatment. The clear filtrate obtained after carbon treatment was cooled to 10oC to 15oC then basified to pH 9.5 to 10 by liquor ammonia reaction mass and further stirred for 30 minutes at a temperature in the range of 10oC to 15oC. The isolated Ketamine base was filtered followed by washing with water (200 litre) and total yield of 290 to 330 kg of wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Shall be consumed for next steps in preparation of one or more crystalline forms of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

[0039] FIG. 2 shows small crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure. According to an embodiment of the present invention, the process of preparation of the small crystal like polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding of wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% aqueous isopropyl alcohol to obtain a reaction mass, adjusting the moisture of the reaction mass to 8.0% to 10%, heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment, cooling the carbon treated filtrate at a temperature of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid solution, distillation of the isopropyl alcohol from the reaction mass, cooling the reaction mass at a temperature in the range of 5oC to 10oC, filtering the reaction mass to isolate the product and drying the isolated product at a temperature in the range of 80oC to 85oC to obtain small crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.
EXAMPLE-3
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride (Ketamine hydrochloride) Small Crystals
[0040] In reactor, wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone (600kg on dry basis) to 2100 litres of 4.0% to 6.0% aqueous isopropyl alcohol. Next, the moisture of the reaction mass is heated to a temperature in the range of 60oC to 65oC followed by 15kg of activated carbon treatment. Further, the carbon treated filtrate is chilled in the temperature range of 15oC to 20oC and acidified to pH 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid solution (NLT 24.0% of HCL content by titration) at temperature range of 15oC to 20oC. The resultant reaction mass was maintained for 30mins followed by the distillation of isopropyl alcohol from reaction mass to about 2000 litres to 2300 litres atmospherically. Next, the reaction mass was then chilled to 5oC to 10oC. The isolated material is then filtered followed by chilled IPA washing. Finally, after drying the isolated material at temperature range of 85oC, the small Crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride (Ketamine Hydrochloride) was obtained and the total yield rate is about 87.50% (525 kg).

[0041] FIG. 3 shows sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure. According to an embodiment of the present invention, the process for preparation of the sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding the wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone to 4.0% to 6.0% an aqueous isopropyl alcohol to obtain a reaction mass, adjusting the moisture of the reaction mass to 8.0% to 10.0%, heating the reaction mass at a temperature in the range of 60oC to 65oC followed by activated carbon treatment, cooling the carbon treated reaction mass at a temperature in the range of 15oC to 20oC and adjusting the pH to 0.8 to 1.5 by addition of isopropyl alcohol and hydrochloric acid, heating the reaction mass at a temperature of 78oC and adding of demineralized water to dissolve the solids followed by distillation of isopropyl alcohol to obtain the slurry at the same temperature, cooling the reaction mass at a temperature in the range of 25oC to 30oC, filtering to isolate the product and followed by IPA (Isopropyl alcohol) washing at a lower temperature, drying the isolated product at a temperature in the range of 80oC to 85oC to obtain sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.
EXAMPLE-4
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride (Ketamine hydrochloride) Sugar Like Crystals
[0042] In a reactor, wet 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone obtained from Example – 2, 600 kg (on dry basis) was added to 2100 litre of 4.0% to 6.0% aqueous Isopropyl Alcohol. The moisture of reaction mass was adjusted to 8.0% to 10.0%. The reaction mass was heated to a temperature in the range of 60oC to 65oC followed by 15 kg of activated carbon treatment. The carbon treated filtrate was further chilled to a temperature in the range of 15oC to 20oC and acidified to pH 0.8 to 1.5 by Isopropyl alcohol + Hydrochloric acid solution (NLT 24.0 % of HCl content by titration) at a temperature in the range of 15oC to 20oC. The reaction was maintained for 30 minutes. The reaction mass was heated to a temperature in the range of 78oC and demineralized water was added just to dissolve the solid (8% to 15%) followed by the distillation of Isopropyl alcohol atmospherically from the reaction mass to obtain the slurry at the same temperature. The reaction mass was then chilled to a temperature in the range of 25oC to 30oC. The isolated material was filtered, followed by chilled IPA washing. After drying at a temperature in the range of 80oC to 85oC, the sugar like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride (Ketamine hydrochloride) was obtained.

[0043] FIG. 4 shows rock candy like crystals 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure. According to an embodiment of the present invention, one or more polymorphs can be obtained as rock candy like crystals by dissolving the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in three fold volume of methanol at a temperature in the range of 60oC to 65oC, wherein the crystals can be obtained without disturbing the reaction mass for a time period of 20 to 40 hours. More specifically, the process comprises of adding of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to methanal, heating the reaction mass at a temperature in the range of 60oC to 65oC, cooling the reaction mass overnight and removing rock candy like crystals, concentrating the mother liquor at a temperature of 45oC under vacuum till occurrence of turbidity, heating the reaction mass at a temperature of 60oC to 65oC to get clear reaction mass, cooling the reaction mass overnight without any disturbance and drying, milling and sieving to obtain rock candy like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

EXAMPLE-5
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride
Rock Candy Like Crystals
[0044] Ketamine Hydrochloride obtained from Example – 3 was added to methanol. Steam was applied to heat the reaction mass at 60oC to 65oC. The clear reaction mass was then transferred hot in the HDPE (High Density Polyethylene) drums. The contents from the drums was allowed to cool overnight naturally without disturbing, this may get prolonged to get the desired crystals. The rock candy like crystals formed are removed from drums. The Mother liquor was concentrated up to 45oC under vacuum till turbidity occurred. Again, the reaction mass is heated to 60oC to 65oC to get clear reaction mass. Then reaction mass was transferred to HDPE drums followed by naturally cooling for overnight or more time without disturbing. After drying, milling & sieving the rock candy like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride was obtained.

[0045] FIG. 5 shows needle like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in accordance with an embodiment of the present disclosure. According to an embodiment of the present invention, needle shaped crystals can be obtained by dissolving the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride in a volume of water (1.7 folds) at a temperature in the range of 70oC to 75oC. The reaction mass is agitated continuously at the rate of 100 and subsequently cooled slowly up to a temperature of 55oC in a time period of 24 to 26 hours and then up to 30oC to 40oC in 10 to 18 hours.

[0046] More specifically, the process of preparation of needle like crystal polymorph of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride comprises of adding of the 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride to a demineralized water at a room temperature, heating the reaction mass at a temperature in the range of 60oC to 75oC for achieving complete dissolution, cooling the reaction mass at a temperature in the range of 55oC in 24 to 26 hours, adding water to the reaction mass at regular intervals to cool the contents at a temperature in the range of 30oC to 40oC for over 10 to 18 hours, filtering the isolated needle type crystal by washing with isopropyl alcohol, collecting water from the mother liquor and repeating the previous steps for seven times; and drying and sieving the needle like crystals of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride.

EXAMPLE-6
Preparation of 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone Hydrochloride
Needle Like Crystals
[0047] In a 0.5 KL of single walled glass assembly immersed in a water bath, fitted with motor operated overhead stirrer, two half-moon type Teflon blades, 200 kg of Ketamine Hydrochloride obtained from Example – 3 was added to 340 litre demineralized water at room temperature. The reaction mass was heated to a temperature in the range of 60oC to 75oC to make it completely dissolved. The RPM (revolutions per minute) of a stirrer was adjusted to be at 100. Then the reaction mass was allowed to cool to a temperature of 55oC in 24 to 26 hours naturally. The room temperature water was applied for 10 minutes to reaction mass at the regular intervals of every hour to cool the content to a temperature in the range of 30oC to 40oC (more preferably to 40oC) in 10 to 18 hours. The isolated needle type crystal was then filtered through nutsche filter followed by washing with 30 litre filtered Isopropyl alcohol. The water from the mother liquor was collected through cartridge filter in the same assembly. To this 100 kg of Ketamine Hydrochloride obtained from the method described in the Example - 3 was added. The reaction mass was heated to 60oC to 75oC to make it completely dissolved. The RPM of a stirrer was adjusted to 100. Then the reaction mass was allowed to cool to a temperature of 55oC in 24 to 26 hours naturally. The room temperature water was applied for 10 minutes to the reaction mass at the intervals of every hour to cool the content to 30oC to 40oC (more preferably to 40oC) in 10 to 18 hours. The isolated needle type crystal was then filtered through nutsche filter followed by washing with filtered Isopropyl alcohol. Like this 100 kg of Ketamine Hydrochloride top up was done up to VII lots. The Needles obtained thus was dried carefully in a trey dryer at a temperature in the range of 60oC to 75oC followed by sieving. (70% to 90% of the Input Quantity).

[0048] The crystalline form of a 2-(2-chlorophenyl)-2-(methylamino) cyclohexanone hydrochloride obtained using the process of present invention is cheaper, efficient and further different types of crystals required for different formulations can be obtained.

[0049] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

[0050] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependant on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.