Claims:1. An adduct having formula RCOOH…R’,
wherein R represents linear, branched; substituted aliphatic, unsubstituted aliphatic, substituted aromatic, unsubstituted aromatic, substituted heterocyclic compounds and un-substituted heterocyclic compounds and R’ represents a Lewis base;
wherein ‘RCOOH…R’ represents a bond between R’ and RCOOH, selected from the group consisting of dipole-dipole interaction, hydrogen-bond, covalent coordinate bond, coordinate bond, polar covalent bond and bonds formed by Van der Waal forces.

2. The adduct as claimed in claim 1, wherein RCOOH is selected from the group consisting of terephthalic acid, orthophthalic acid, 4-formyl benzoic acid, p-toluic acid and naphthenic acid.

3. The adduct as claimed in claim 1, wherein said Lewis base is at least one selected from the group consisting of linear and branched, substituted and non-substituted mono, di and trialkyl amine and phosphine, linear and branched substituted and non-substituted mono and dialkyl sulfide, substituted and non-substituted imidazole, pyrazole, thiazole, isothiazole, azathiozole, oxothiazole, oxazine, oxazoline, oxazaborole, dithiazole, triazole, selenozole, oxahosphole, pyrrole, borole, furan, thiophene, phosphole, pentazole, indole, indoline, oxazole, isothirazole, tetrazole, benzofuran, dibenzofuran, benzothiophene, dibenzothoiphene, thiadiazole, pyridine, pyrimidine, pyrazine, pyridazine, piperazine, piperidine, morpholine, pyran, aniline, phthalazine, quinazoline, quinoxaline, tromethamine, triethanolamine, pyrrolidine 1-(2-hydroxyethyl), morpholine 4-(2-hydroxyethyl), L-lysine, hydrabamine, N-methyl glucamine, ethylene diamine, ethanoamine, 2-dimethylamino ethanol, diethanolamine, deanol, choline, benzathine, benethamine, L-arginine, ammonia, imidazolidones, oxazolidinones and derivatives, hydantoins, urazoles, oxazolidines, isoxazolidines and benzisox, pyrazolidines, 2H-azirines, 2-azetines, 3-pyrrolines, 2-pyrrolines, 1-pyrrolines, maleimides, 2-isoxazolines, 2-oxazolines, 3-oxazolines, 2-imidazolines, thiazolines, pyrazolines, 3-pyrazolines, benzimidazoles,indazoles, 1,2,3-triazoles, benzotriazoles, 1,2,4-triazoles, tetrazoles, imidazol-2-ones, benzimidazol-2-ones, imidazol-5-ones, 2-oxazolones, benzoxazoles, isoxazoles, benzisoxazoles, 1,3,4-oxadiazoles, 1,2,4-oxadiazoles, benzothiazoles, 1,3,4 thiadiazoles, 1,2,4-thiadiazoles, substituted N-heterocycles, oxindoles, indolenines, isatins, azaindoles, isoindoles, isoindolinones, carbazoles, indolizines, indolizinones and related compounds, dihydro-pyridines, 2-pyridones, 1,3,5-triazines, quinolines and related compounds, tetrahydro-quinolines, 1,2-dihydroquinolines, isoquinolines and related compounds, 3,4-dihydroisoquinolines, tetrahydroisoquinolines, 1,8-naphthyridines, quinazolines, quinoxalines, tetrahydro-quinoxalines, 2,3-dihydro-4-pyridones, 4-quinolones, quinazolinones, azepines, saturated heterocyclic compounds, unsaturated heterocyclic compounds and any combination thereof.

4. The adduct as claimed in claim 1, wherein said Lewis base is 1-methyl imidazole.

5. A process for the preparation of the adduct as claimed in claim 1, said process comprising the following steps:
a. reacting RCOOH with R’ in a mole ratio ranging from 1:1 to 1:50 to form adduct(s) in a dissolved form in a resultant mass;
b. crystallizing at least one adduct from said resultant mass to obtain crystals of at least one adduct; and
c. separating said crystals of the adduct from the resultant mass to obtain separated crystals of the adduct.

6. The process as claimed in claim 5, wherein the reaction in step (a) is carried out in the temperature range of 50 oC to 200 oC and in the pressure range of 1 bar to 10 bar.

7. The process as claimed in claim 5, wherein crystallization in step (b) is carried out at a temperature lower than the temperature at which the reaction in step (a) is carried out. , Description:This is an application for a Divisional Patent to Indian Patent Application No. 1837/MUM/2014 filed on 4th June 2014, the entire contents of which are specifically incorporated herein by reference.
FIELD
The present disclosure relates to Lewis base-carboxylic acid adducts and processes for their preparation.
BACKGROUND
Recently, various aromatic dicarboxylic acids have become commercially important in view of the fact that these aromatic dicarboxylic acids undergo condensation polymerization reactions with various diols, such as ethylene glycol, and the like, to form polymers. These polymers are capable of being formed into fibers and filaments. The filaments thus produced have many commercial applications
In view of the above, it is recommended that pure dicarboxylic acid be used in condensation polymerization, in order to achieve polymers with desirable properties. Hence, purified carboxylic acids are industrially important as starting material for condensation polymerization. Conventionally available methods for purifying crude carboxylic acid are not completely satisfactory either from an engineering or an economic standpoint. Yet the purity of carboxylic acids is an important factor in the formation of polyester resin.
US2949483, by Ham, et al discloses the process of dissolving terephthalic acid in N-methyl-2-pyrrolidinone and precipitating a “salt complex” containing terephthalic acid and N-methyl-2-pyrrolidinone. The solid is washed with water to remove the N-methyl-2-pyrrolidinone and yield purified terephthalic acid. US2949483 claims a recovery rate of about 60% of the weight of crude terephthalic acid.
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 is to provide an adduct of Lewis base-carboxylic acid.
Another object of the present disclosure is to provide a process for preparing an adduct of Lewis base-carboxylic acid.
Still another object of the present disclosure is to provide a simple process for preparing the adduct of Lewis base-carboxylic acid..
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a Lewis base-carboxylic acid adduct and a process for its preparation. Lewis base-carboxylic adducts play important role in the purification of carboxylic acid.
The present disclosure relates to an adduct having formula RCOOH…R’ and the process for preparing the same, wherein RCOOH represents a carboxylic acid and R’represents a Lewis base. The process for preparing the adduct involves the steps of reacting RCOOH with R’ in a mole ratio ranging from 1:1 to 1:50 to form adduct(s) in a dissolved form in a resultant mass; crystallizing the adducts to obtain crystals of the adduct; and separating said crystals of the adduct from the resultant mass to obtain separated crystals of the adduct.
The adduct obtained by the process of the present disclosure is a Lewis base-carboxylic acid adduct.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Figure 1 illustrates the structure of an adduct of 1-methyl imidazole-terephthalic acid in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates to a Lewis base-carboxylic acid adduct and a process for preparing the same.
In accordance with one aspect of the present disclosure, the adduct has a formula RCOOH…R’ in which RCOOH is a carboxylic acid and R’ is a Lewis base.
RCOOH is a carboxylic acid, at least one selected from the group consisting of terephthalic acid, orthophthalic acid, 4-formyl benzoic acid, p-toluic acid, naphthenic acid, and mixtures thereof. In RCOOH, R represents linear, branched, substituted aliphatic, unsubstituted aliphatic, substituted aromatic, un-substituted aromatic, substituted heterocyclic compounds, and un-substituted heterocyclic compounds
R’ is a Lewis base is at least one selected from the group consisting of linear and branched, substituted and non-substituted mono, di and trialkyl amine and phosphine, linear and branched substituted and non-substituted mono and dialkyl sulfide, substituted and non-substituted imidazole, pyrazole, thiazole, isothiazole, azathiozole, oxothiazole, oxazine, oxazoline, oxazaborole, dithiazole, triazole, selenozole, oxahosphole, pyrrole, borole, furan, thiophene, phosphole, pentazole, indole, indoline, oxazole, isothirazole, tetrazole, benzofuran, dibenzofuran, benzothiophene, dibenzothoiphene, thiadiazole, pyridine, pyrimidine, pyrazine, pyridazine, piperazine, piperidine, morpholine, pyran, aniline, phthalazine, quinazoline, quinoxaline, tromethamine, triethanolamine, pyrrolidine 1-(2-hydroxyethyl), morpholine 4-(2-hydroxyethyl), L-lysine, hydrabamine, N-methyl glucamine, ethylene diamine, ethanolamine, 2-dimethylamino ethanol, diethanolamine, deanol, choline, benzathine, benethamine, L-arginine, ammonia, imidazolidones, oxazolidinones and derivatives, hydantoins, urazoles, oxazolidines, isoxazolidines and benzisox, pyrazolidines, 2H-azirines, 2-azetines, 3-pyrrolines, 2-pyrrolines, 1-pyrrolines, maleimides, 2-isoxazolines, 2-oxazolines, 3-oxazolines, 2-imidazolines, thiazolines, pyrazolines, 3-pyrazolines, benzimidazoles,indazoles, 1,2,3-triazoles, benzotriazoles, 1,2,4-triazoles, tetrazoles, imidazol-2-ones, benzimidazol-2-ones, Imidazol-5-ones, 2-oxazolones, benzoxazoles, isoxazoles, benzisoxazoles, 1,3,4-oxadiazoles, 1,2,4-oxadiazoles, benzothiazoles, 1,3,4 thiadiazoles, 1,2,4-thiadiazoles, substituted N-heterocycles, oxindoles, indolenines, isatins, azaindoles, isoindoles, isoindolinones, carbazoles, indolizines, indolizinones and related compounds, dihydro-pyridines, 2-pyridones, 1,3,5-triazines, quinolines and related compounds, tetrahydro-quinolines, 1,2-dihydroquinolines, isoquinolines and related compounds, 3,4-dihydroisoquinolines, tetrahydroisoquinolines, 1,8-naphthyridines, quinazolines, quinoxalines, tetrahydro-quinoxalines, 2,3-dihydro-4-pyridones, 4-quinolones, quinazolinones, azepines, saturated heterocyclic compounds, unsaturated heterocyclic compounds and any combination thereof.
In an exemplary embodiment of the present disclosure, the Lewis base is 1-methyl imidazole.
In the present disclosure R’ is loosely bonded to RCOOH by a bond selected from dipole-dipole interaction, H-bonding, covalent coordination bonding, coordination bonding, polar covalent bonding and bonding by Van der Waal forces.
In accordance with another aspect of the present disclosure there is provided a process for the preparation of the adduct.
In the first step, at least one carboxylic acid is reacted with at least one Lewis base at a temperature in the range of 50 oC to 200 oC and at a pressure ranging from 1 bar to 10 bar to obtain an adduct in dissolved form in the resultant mass. The adduct appears as homogenous solution, i.e. it is completely dissolved in the resultant mass. More than one adduct may be formed in the reaction.
Typically, the carboxylic acid is crude carboxylic acid, which is selected from the group consisting of crude terephthalic acid, crude orthophthalic acid, crude 4-formyl benzoic acid, crude p-toluic acid, crude naphthenic acid, and mixtures thereof.
The molar ratio of the carboxylic acid to the Lewis base ranges from 1:1 to 1:50. The quantity of crude carboxylic acid to the Lewis base ratio is such that all adducts that are formed of carboxylic acid, its intermediates and impurities remain in soluble form at a temperature ranging between 50 oC and 200 oC.
When the Lewis base is reacted with crude carboxylic acid at the afore-stated temperature and pressure conditions, Lewis base-carboxylic acid adducts are formed in a dissolved form in a resultant mass. The Lewis base-carboxylic acid adducts that can be formed include, but are not limited to, Lewis base-terephthalic acid adduct, Lewis base-orthophthalic acid adduct, Lewis base-4-formyl benzoic acid, Lewis base-p-toluic acid, Lewis base-naphthenic acid and the like.
The adduct formation takes place due to dipole-dipole interaction between the nitrogen atom of the 1-methyl imidazole and hydrogen atom of carboxylic acid group. An embodiment of the afore-stated adduct - an adduct between the nitrogen atom of the 1-methyl imidazole and hydrogen atom of terephthalic acid is represented in Figure 1.
The so obtained homogenous (clear) solution of the resultant mass containing the adduct of Lewis base-carboxylic acid undergoes crystallization at a temperature lower than the temperature at which the reaction of Lewis base with a crude carboxylic acid (adduct formation) is carried out to obtain the crystals of at least one adduct of the carboxylic acid. In an exemplary embodiment, the adduct of Lewis base-carboxylic acid is Lewis base- terephthalic acid adduct and Lewis base-orthophthalic acid adduct.
The crystals obtained in the above step are separated by filtering the solids from the mother liquor or decanting the mother liquor followed by washing the crystals optionally with the fluid medium to obtain separated crystals of Lewis base-carboxylic acid. In an exemplary embodiment, the separated crystals are the crystals of Lewis base-terephthalic acid adduct, Lewis base-orthophthalic acid, Lewis base-4-formyl benzoic acid, Lewis base-p-toluic acid and Lewis base-naphthenic acid.
The washing fluid medium is at least one selected from the group consisting of methyl acetate, ethyl acetate, acetonitrile, dichloromethane, dichloroethane, 1-methyl imidazole and combination thereof.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments 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 embodiments herein. The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale.
Experimental details:
Example 1:
49.8 grams of crude terephthalic acid were mixed with 147.78 grams of 1-methyl imidazole in 1:6 mole ratio at temperature 105 oC. After cooling to 27-30 oC, solid adduct was obtained. The solid (adduct) was filtered and washed with methyl acetate. A white colored adduct of 1-methyl imidazole- terephthalic acid was observed.
The adduct was characterized by X-Ray crystallography and the results obtained are provided herein below-
Characterization data for 1-methyl imidazole- terephthalic acid adduct in accordance with the present disclosure:
Empirical Formula C16H18N4O4
Formula Weight /g mol-1 330.34
Color Colorless
Crystal System Monoclinic
Space group P21/n
a A 6.601(2)
b/A 12.236(4)
c/A 10.533(3)
a/° 90
p/° 101.601(7)
y/° 90
V/A3 833.3(5)
F(000) 374
Z 10
pcalc/gcm-3 1.458
Absorption Coeeficient/mm-1 0.131
0 range for data collection^ 2.582 - 26.370
Reflections Collected 8600
Independent Reflections 1702 (Rint for equivalents = 0.0237)

Reflections with I>2ai 1490
Parameters refined 111
Completeness to 9max/% 100
Largest diff. peak and hole/e-
A-3 0.187, -0.340
Rl, wR2 (I>2ai) 0.0455, 0.1558
Rl, wR2 (all data) 0.0505, 0.1645

2. Hydrogen Bonding Parameters
O1-H2--N2 = 1.770 A
O1--N2 = 2.590 A
< O1-H2-N2 = 177.11°

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
• generating purified adduct of Lewis base-carboxylic acid.
• purification of adduct of Lewis base-carboxylic acid using moderate temperature and atmospheric pressure.
• purification of adduct of Lewis base-carboxylic acid using reusable and recyclable chemicals
The exemplary embodiments herein quantify the benefits arising out of this disclosure and the various features and advantageous details thereof are explained with reference to 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 herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing 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 has 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.
Any discussion of documents, acts, materials, devices, articles and 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.
While considerable emphasis has been placed herein on the particular features of this disclosure, 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 disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitations.