Claims:1. An ionic liquid comprising at least one heterocyclic amine, a first metal salt and a second metal salt, wherein the heterocyclic amine is selected from the group consisting of imidazole, azole, pyridine, pyrrole, triazole, oxazole, oxadiazole, benzimdazole, carbazole, pyrimidine, pyridazine, pyrrolidine, piperidine, morpholine, and their substituted analogues.

2. The ionic liquid as claimed in claim 1, wherein the molar ratio of the first metal salt and the heterocyclic amine is in the range from 1:10 to 10:1; and the molar ratio of the second metal salt and the heterocyclic amine is in the range from 1:10 to 10:1.

3. The ionic liquid as claimed in claim 1, wherein the metal in each of the first metal salt and the second metal salt, is selected independently from the group consisting of Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg.

4. The ionic liquid as claimed in claim 1, wherein the first metal salt and the second metal salt each are independently selected from a group salts consisting of chloride, bromide, iodide, sulfate, acetate, and chromate.

5. The ionic liquid as claimed in claim 1, wherein the first metal salt and the second metal salt are independently selected from a group of metal salts consisting of aluminum trichloride (AlCl3), ferric chloride (FeCl3), and chromium chloride (CrCl3).

6. The ionic liquid as claimed in claim 1, wherein the first metal salt and the second metal salt are the same.

7. The ionic liquid as claimed in claim 1, wherein the heterocyclic amine is imidazole.

8. The ionic liquid as claimed in claim 1, wherein the ionic liquid comprises at least one fluid medium selected from the group consisting of benzene, toluene, xylene, chlorobenzene, nitrobenzene, and substituted benzene compounds.
9. A process for the preparation of the ionic liquid of claim 1, said process comprises the following steps:
? mixing a predetermined amount the first metal salt and at least one heterocyclic amine followed by agitating to form an adduct; and
? adding a predetermined amount of the second metal salt to the adduct and stirring to form the ionic liquid. , Description:FIELD
The present disclosure relates to ionic liquids.
BACKGROUND
Ionic liquids are increasingly finding applications as catalysts, solvents and electrolytes in diverse areas such as synthesis of chemical compounds, electrochemistry, photovoltaic devices, electro-deposition processes, and semi-conductor cleaning.
The ionic liquids exhibit low vapor pressure, have high ionic conductivity and have low flammability. Due to these advantages, they are used in place of conventional molecular solvents.
Ionic liquids comprise anionic components and cationic components that interact with each other. These components and their relative amounts determine physico-chemical properties of the ionic liquids such as the polarity, thermal stability, conductivity and viscosity. The utility of an ionic liquid depends upon its physico-chemical properties.
The art continues to develop ionic liquids having tunable activity. Further, ionic liquids are associated with drawbacks such as high cost and tedious methods of preparation.
Thus, there is felt a need to provide inexpensive ionic liquids having tunable activity. Further, it is desired that the ionic liquids are prepared by a simple process.
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 prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide an ionic liquid.
Another object of the present disclosure is to provide an inexpensive ionic liquid having tunable activity.
Yet another object of the present disclosure is to provide an ionic liquid prepared by a simple process.
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
In one aspect, the present disclosure provides an ionic liquid comprising at least one heterocyclic amine, a first metal salt and a second metal salt. The heterocyclic amine can be selected from the group consisting of imidazole, azole, pyridine, pyrrole, triazole, oxazole, oxadizole, benzimdazole, carbazole, pyrimidine, pyridazine pyrrolidine, piperidine, morpholine, and their substituted analogues.
The metal in each of the first metal salt and second metal salt, can be independently selected from the group consisting of Al, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg.
The process for the preparation of the ionic liquids of the present disclosure involves preparation of an adduct by mixing a first metal salt and a heterocyclic amine. This adduct is then mixed with a second metal salt to form ionic liquid of the present disclosure. Thus, the process of the present disclosure is simple. Ionic liquid of requisite activity can be obtained by selection of heterocyclic amine and metal salts.
The ionic liquid of the present disclosure can be used for various reactions such as alkylation, trans-alkylation, acylation, Diel-Alder reaction, and Friedel-Craft reaction.
DETAILED DESCRIPTION
An object of the present disclosure is to provide inexpensive ionic liquids having tunable activity. The present disclosure envisages ionic liquids prepared using heterocyclic amines and metal salts. Ionic liquid of requisite activity can be obtained by selection of appropriate heterocyclic amine and metal salts, and their relative amounts.
In accordance with one aspect the present disclosure provides an ionic liquid comprising at least one heterocyclic amine, a first metal salt and a second metal salt.
In accordance with the embodiments of the present disclosure, the heterocyclic amine can be selected from the group consisting of imidazole, azole, pyridine, pyrrole, triazole, oxazole, oxadiazole, benzimdazole, carbazole, pyrimidine, pyridazine, pyrrolidine, piperidine, morpholine, and their substituted analogues.
In accordance with an exemplary embodiment of the present disclosure, the heterocyclic amine is imidazole.
In accordance with the embodiments of the present disclosure, the metal in each of the first metal salt and the second metal salt, can be selected independently from the group consisting of Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg.
In accordance with one embodiment of the present disclosure, the metal can be Aluminum (Al).
In accordance with another embodiment of the present disclosure, the metal can be Iron (Fe).
In accordance with still another embodiment of the present disclosure, the metal can be Chromium (Cr).
The salts of other metals such as Mg, Mn, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg, that interact in a way similar to Al, Fe and Cr and form ionic liquids, are envisioned in accordance with the present disclosure.
In accordance with the embodiments of the present disclosure, the first metal salt and the second metal salt each can independently be selected from a group of salts consisting of chloride, bromide, iodide, sulfate, acetate, and chromate.
In accordance with one embodiment of the present disclosure, the salt is a chloride salt.
Other salts such as bromide, iodide, sulfate, acetate, and chromate of the metal that interact in a way similar to chloride and form ionic liquids, are envisioned in accordance with the disclosure.
In accordance with the embodiments of the present disclosure, the first metal salt and the second metal salt can be the same.
In accordance with the embodiments of the present disclosure, the first metal salt and the second metal salt can be different.
The ionic liquids of the present disclosure are prepared using inexpensive starting materials.
In accordance with the embodiments of the present disclosure, the molar ratio of the first metal salt and the heterocyclic amine can be in the range from 1:10 to 10:1. The molar ratio of the second metal salt and the heterocyclic amine can be in the range from 1:10 to 10:1.
In accordance with one exemplary embodiment of the present disclosure, the molar ratio of the heterocyclic amine to the first metal salt is 3:1.
In accordance with another exemplary embodiment of the present disclosure, the molar ratio of the heterocyclic amine to the first metal salt is 1:1.
In accordance with one exemplary embodiment of the present disclosure, the molar ratio of the heterocyclic amine to the second metal salt is 1:3.6.
In accordance with another exemplary embodiment of the present disclosure, the molar ratio of the heterocyclic amine to the second metal salt is 1:1.
One part of the metal salts take part in the adduct formation, whereas the remaining amount of the metal salt remains free in the ionic liquid and is capable of acting as a Lewis acid. The amount of the free metal salt is dependent on the molar ratio of the amount of metal salt and the amount of the heterocyclic amine. Therefore, the Lewis acidity of the ionic liquids of the present disclosure can be tuned by selection of appropriate metal salt/s and their molar ratio with regard to the heterocyclic amine. The ionic liquids of the present disclosure can be useful in chemical reactions that are catalyzed by Lewis acids.
The ionic liquid of the present disclosure can be used for various reactions such as alkylation, trans-alkylation, acylation, Diel-Alder reaction, and Friedel-Craft reaction.
In accordance with the embodiments of the present disclosure, the ionic liquid comprises at least one fluid medium selected from the group consisting of benzene, toluene, xylene, chlorobenzene, nitrobenzene, and substituted benzene compounds.
The ionic liquids of the present disclosure are found to have high thermal stability.
In accordance with the second aspect of the present disclosure, there is provided a process for the preparation of the ionic liquids of the present disclosure. The process comprises the following steps.
First, a predetermined amount a first metal salt and at least one heterocyclic amine are mixed and agitated to form an adduct. A predetermined amount of a second metal salt is added to the adduct followed by stirring to form the ionic liquid of the present disclosure.
In accordance with the embodiments the present disclosure, in the process of preparation of the ionic liquids, the adduct formation step can optionally be carried out in a second fluid medium comprising at least one solvent selected from the group consisting of dichloromethane, dichloroethane, chloroform, ethanol, methanol, and propanol. Once the adduct formation is complete, the adduct is separated from the second fluid medium and dried under reduced pressure.
The disclosure will now be described with reference to the following laboratory experiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The laboratory scale experiments provided herein can be scaled up to industrial or commercial scale.
Experiments
The ionic liquids of the present disclosure are prepared in the form of a eutectic mixture and as a solution in a fluid medium.
Experiment 1:
Step 1: To a reactor, maintained under nitrogen atmosphere and immersed in a water bath maintained at room temperature, was introduced anhydrous aluminum trichloride (AlCl3) (6.5 g) followed by imidazole (9.94 g). An exothermic reaction ensued. The reaction mixture was gently agitated to obtain a white solid adduct of Imidazole-AlCl3.
Step 2: In a reactor, maintained under nitrogen atmosphere, was introduced Imidazole-AlCl3 adduct (5.0 g) obtained in step 1 of experiment 1 and AlCl3 (11.87 g), at room temperature. The resulting mixture was stirred for 3.5 hours to obtain a homogeneous eutectic liquid.

Experiment 2:
STEP 1: In a reactor, maintained under nitrogen atmosphere, anhydrous imidazole (0.5 g) was dissolved in dichloromethane (10ml), and absolute ethanol (1 ml) as fluid media followed by addition of anhydrous FeCl3 (1.19g). The reaction mixture was stirred for 20 min, brown colored solid started precipitating. After complete reaction, the precipitated brown solid was filtered and dried in oven at 50oC under reduced pressure.
STEP 2: To a reactor, maintained under nitrogen atmosphere, 0.5 g solid obtained in step-1 of experiment 2 was mixed with anhydrous FeCl3 ¬(0.35g) and stirred for 1 hour to obtain the ionic liquid without a fluid medium.

Experiment 3:
To a reactor, maintained under nitrogen atmosphere, 0.5 g solids obtained in experiment-2 step-1 was mixed with anhydrous FeCl3 (0.35g) and anhydrous benzene (5g) as a fluid medium followed by stirring for 1 hour to obtain the ionic liquid in benzene.

Experiment 4:
STEP 1: In a reactor, maintained under nitrogen atmosphere, was dissolved anhydrous imidazole (0.5 g) in dichloromethane (10 ml) and absolute ethanol (1 ml) as fluid medium. Anhydrous CrCl3 (1.16g) was added and the reaction mixture was stirred for 20 min when brown colored solid started precipitating. After completion of the reaction, the precipitated brown solid was filtered and dried in oven at 50oC under reduced pressure.
STEP 2: To a reactor, maintained under nitrogen atmosphere, 0.5 g solid obtained in experiment 4 (step 1) was mixed with 0.34 g anhydrous CrCl3, and stirred for 1 hour to obtain the ionic liquid without a fluid medium.

Experiment 5:
To a reactor under nitrogen atmosphere, 0.5 g solid obtained in experiment 4 (step 1) was mixed with anhydrous CrCl3 (0.34g) and anhydrous benzene (5g) as a fluid medium and stirred for 1 hour to obtain the ionic liquid in benzene.
Thus, the process of the present disclosure provides ionic liquids in a simple process.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above have several technical advantages including, but not limited to, the realization of:
? inexpensive ionic liquids;
? a simple process for the preparation of the ionic liquids;
? ionic liquids having high temperature stability; and
? ionic liquids having tunable Lewis acidity.

The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
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.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
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.
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 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.