DESC:FIELD
The present disclosure relates to a process for preparing 4,4’-biphenol.
BACKGROUND
Biphenol is a phenolic derivative of biphenyl. Biphenol is used as an intermediate in the manufacture of thermoplastics such as liquid crystalline polymers (LCP), polyesters, polycarbonates and polysulfones.

4,4'-biphenol

Various methods are known for the production of 4,4'-biphenol. One of the earlier method to prepare 4,4'-biphenol involves diazo decomposition of benzidine. Recently 4,4'-biphenol is prepared by dealkylation of tetra-tert-butyldiphenol. However, the conventional processes use raw materials that are expensive and require severe operating conditions. Furthermore, these processes are low yielding.
Therefore, there is felt a need for a process for the preparation of 4,4'-biphenol that is simple and economic and gives a high yield of 4,4'-biphenol.
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 a process of preparation of Biphenol.
Another object of the present disclosure is to provide a process of preparation of bromophenol.
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 accordance with one aspect of the present disclosure, there is provided a process for the preparation of 4,4’-biphenol, the process comprising the following steps:
? a reactor is charged with an aqueous solution of at least one base and a predetermined amount of p-bromophenol to obtain a first mixture, which is heated at a temperature in the range of 50 to 100 °C and is allowed to stand for a predetermined time period to obtain a heated first mixture; a predetermined amount of at least one catalyst is added to the heated first mixture to obtain a second mixture, which is heated at a temperature in the range of 50 to 100 °C to obtain a heated second mixture; a predetermined amount of at least one reducing agent selected from an aqueous solution of hydroxylamine sulfate and an aqueous solution of hydroxylamine hydrochloride is introduced in the heated second mixture under inert atmosphere to obtain a third mixture, which is heated at a temperature in the range of 50 to 100 °C for a time period in the range of 30 to 180 minutes to obtain a reaction mass; the reaction mass is cooled to a temperature in the range of 30 to 60 °C under inert atmosphere and the reaction mass is filtered followed by washing to obtain a first solid; the first solid mass is treated with a mineral acid under inert atmosphere to obtain a slurry; the slurry is heated at a temperature in the range of 40 to 70 °C for a time period in the range of 30 to 180 minutes and filtered to obtain a second solid; and the second solid is washed with hot water to obtain 4,4’-Biphenol.
In accordance with another aspect of the present disclosure, there is provided a process for the preparation of p-bromophenol, the process comprising the steps of:
? a fluid medium and phenol is charged into a reactor at a temperature in the range of 0 to 10 °C under stirring to obtain a first mixture; adding a solution of bromine and the fluid medium to the first mixture over a time period in the range of 6 to 8 hours to obtain a second mixture; the second mixture is allowed to stand at a temperature of 0 to 10 °C for 1 to 2 hours to obtain a third mixture; water is added to the third mixture and allowed to stand for a time period in the range of 20 to 40 minutes to obtain a biphasic mixture; the two layers of the biphasic mixture are separated and the organic layer is washed in a step wise manner with aqueous sodium thiosulfate and aqueous sodium bicarbonate to obtain an organic solution; concentrating said organic solution to recover ethylene dichloride to obtain the organic concentrate; purifying the organic concentrate to obtain a purified organic concentrate; and crystallizing the purified organic concentrate using a solvent which includes, but is not limited to, toluene to obtain p-bromophenol.

DETAILED DESCRIPTION
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.
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.
The present disclosure relates to the process of preparation of 4,4’-biphenol, wherein p-bromophenol is subjected to biaryl coupling reaction using at least one base along with Pd/C as a catalyst and at least one reducing agent selected from hydroxylamine sulfate [(NH2OH)2H2SO4] and hydroxylamine hydrochloride followed by acidification to obtain 4,4’-biphenol.
In accordance with one aspect of the present disclosure, there is provided a process for the preparation of 4,4’-biphenol, the process comprising the following steps:
? a reactor is charged with an aqueous solution of at least one base and a predetermined amount of p-bromophenol to obtain a first mixture;
? the first mixture is heated at a temperature in the range of 50 to 100 °C for a time period in the range of 5 to 60 minutes and is allowed to stand for a predetermined time period to obtain a heated first mixture;
? predetermined amount of at least one catalyst is added to the heated first mixture to obtain a second mixture;
? the second mixture is heated at a temperature in the range of 50 to 100 °C to obtain a heated second mixture;
? predetermined amount of at least one reducing agent selected from an aqueous solution of hydroxylamine sulfate and an aqueous solution of hydroxylamine hydrochloride is introduced in the heated second mixture under inert atmosphere to obtain a third mixture;
? the third mixture is heated at a temperature in the range of 50 to 100 °C for a time period in the range of 30 to 180 minutes to obtain a reaction mass;
? the reaction mass is cooled to a temperature in the range of 30 to 60 °C under inert atmosphere and the reaction mass is filtered followed by washing to obtain a first solid;
? the first solid mass is treated with a mineral acid under inert atmosphere to obtain a slurry;
? the slurry is heated at a temperature in the range of 40 to 70 °C for a time period in the range of 30 to 180 minutes and filtered to obtain a second solid; and
? the second solid is washed with hot water to obtain 4,4’-Biphenol.
In accordance with one embodiment of the present disclosure, the catalyst is palladium supported on carbon. The amount of the catalyst used during the reaction is in the range of 1 mol% to 10 mol% of p-bromophenol.
In accordance with the present disclosure, the base is at least one selected from a group consisting of NaOH, KOH and NH4OH.
In accordance with one embodiment of the present disclosure, the base is NaOH.
In accordance with the present disclosure, the ratio of the amount of p-bromophenol and the amount the base is in the range of 1:1 to 1:5.
In accordance with one embodiment of the present disclosure, the ratio of the amount of p-bromophenol and the amount the base is 1:3.
In accordance with the present disclosure, the ratio of the amount of p-bromophenol and the amount of at least one reducing agent selected from hydroxylamine sulfate and hydroxylamine hydrochloride is in the range of 1:0.1 to 1:1.
In accordance with the present disclosure, 0.5 to 1 mole of an acid is used per mole of p-bromophenol.
In accordance with the present disclosure, the acid is at least one selected from a group consisting of H2SO4 and HCl.
The 4,4'-biphenol prepared in accordance with the process of the present disclosure has a purity of 90 to 92%.
In accordance with the present disclosure, at least one reducing agent selected from hydroxylamine sulfate and hydroxylamine hydrochloride act as a reducing agent.
In accordance with another aspect of the present disclosure, there is provided a process for the preparation of p-bromophenol, the process comprising the following steps:
? a fluid medium and phenol is charged into a reactor at a temperature in the range of 0 to 10 °C under stirring to obtain a first mixture;
? adding a solution of bromine and the fluid medium to the first mixture over a time period in the range of 6 to 8 hours to obtain a second mixture;
? the second mixture is allowed to stand at a temperature of 0 to 10 °C for 1 to 2 hours to obtain a third mixture;
? water is added to the third mixture and allowed to stand for a time period in the range of 20 to 40 minutes to obtain a biphasic mixture comprising an organic layer and an aqueous layer;
? the organic layer and the aqueous layer of the biphasic mixture are separated and the organic layer is washed in a step wise manner with aqueous sodium thiosulfate and aqueous sodium bicarbonate to obtain an organic solution;
? concentrating the organic solution to recover ethylene dichloride to obtain the organic concentrate;
? purifying the organic concentrate by distillation to obtain a purified organic concentrate; and
? crystallizing the purified organic concentrate using a solvent which includes, but is not limited to, toluene to obtain p-bromophenol.
In accordance with the present disclosure, the fluid medium is at least one selected from a group consisting of ethylene dichloride, chloroform and acetonitrile.
In accordance with one embodiment of the present disclosure, the fluid medium is ethylene dichloride.
In accordance with the present disclosure, the amount of the fluid medium is in the range of 50 to 300 mL per mole of phenol.
In accordance with the present disclosure, the mole ratio of the amount of phenol and the amount of bromine is in the range of 1:1 to 1:5.
In accordance with one embodiment of the present disclosure, the mole ratio of the amount of phenol and the amount of bromine is 1:1.
In accordance with one embodiment of the present disclosure, the distillation is carried out over a column packed with ceramic.
In accordance with one embodiment of the present disclosure, the organic concentrate is mixed with 2,6-di-t-butyl-p-cresol during distillation.
2,6-di-t-butyl-p-cresol is used as a stabilizer/antioxidant, which reduces the formation of the residue and avoids the decomposition of p-bromophenol.
The GLC analysis of the concentrated mass shows a yield of around 89% for p-bromophenol and less than 5% yield each for o-bromophenol, phenol and dibromophenol.
In an embodiment of the present disclosure, 0.35 mole of aqueous solution of hydroxylamine sulfate is used per mole of p-bromophenol.
The overall progression of the reaction for the preparation of 4,4’-biphenol in accordance with the present disclosure is represented in Scheme 1.

Scheme 1

The present disclosure is further described in light of the following laboratory experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following laboratory scale examples can be scaled up to industrial/commercial scale:
Experiment 1: Preparation of 4-bromophenol
A reactor was charged with 564 g of phenol and 1200 mL of ethylene dichloride maintaining the temperature of the reaction mass at 8 °C under continuous stirring to obtain a first mixture. 768 g bromine diluted with 600 mL of ethylene dichloride was added to the first mixture over the time period of 8 hours, maintaining temperature between 8 to 10 °C to obtain a second mixture. The second mixture was allowed to stand at 8 to10 °C for 90 minutes to obtain a third mixture. 600 mL of water was added to the third mixture and equilibrating the resultant mixture for 30 minutes to obtain the biphasic mixture comprising an organic layer and an aqueous layer. The two layers were separated and the organic layer was washed with 600 mL of 10% Na2S2O3. The organic layer was further washed with 600 mL of water. The organic layer was concentrated to recover ethylene dichloride and the concentrated mass was analyzed by gas-liquid chromatography (GLC).
Weight of concentrated mass = 974 g
The GLC analysis is as given in the Table 1:

Table 1: GLC analysis
Stream GLC analysis
o-bromophenol Phenol dibromophenol 4-bromo-phenol
Concentrated mass 3.17 25.46 1.03 70.17

The overall conversion was 74%. The selectivity for 4-bromophenol and 2-bromophenol were found to be 94.3 % and 4.2 % of the mixture of bromophenols respectively.
p-bromophenol:o-bromophenol ratio = 95:5
Purity by classical analysis = 100%; Yield on purity = 92%
Experiment 2: Preparation of 4,4’-Biphenol

A reactor was charged with 369 g of NaOH in 3000 mL of distilled water and 521 g of 4-bromophenol to obtain a first mixture. The first mixture was heated to 75 °C and maintained at same temperature for 15 minutes to obtain heated first mixture. 6 g of 5% Pd/C was added the heated first mixture to obtain a second mixture. The second mixture was maintained at 75 °C for 15 minutes. A solution of hydroxylamine sulfate (175 g in 360 mL of distilled water) was prepared separately. The solution of hydroxylamine sulfate was added to the second mixture over a time period of 2.5 hours at 80 °C under N2 atmosphere to obtain a third mixture. The third mixture was equilibrated at 80 °C for 1 hour and the bromide content was analyzed.
Bromide content was found to be 102%. The reaction mixture was analyzed using HPLC as its sodium salt. The analysis is as given in Table 2:
Table 2: HPLC analysis
sample HPLC analysis
RT 6.61 RT 8.08 RT 8.99 RT 9.77 RT 10 RT 11.35
RMS-1 0.232 85.96 1.326 6.571 4.54 0.164
The third mixture was cooled to 55 °C under N2 atmosphere and then filtered to obtain a first solid. The first solid was washed with 2X50 mL of hot water.
The first solid was then acidified using 212 g of 98% H2SO4 under N2 atmosphere maintaining the temperature between 45 to 55 °C to obtain a slurry. The slurry was equilibrated at 60 °C for 1 hour and then filtered. A second solid was obtained, which was washed with 2X 250ml of hot water. The second solid was again re-slurried in 1 L of water at 70 °C for 1 hour and filtered at 70 °C. The second solid was washed with hot water and dried to obtain 4,4’-Biphenol.
Weight of solid = 258 g; HPLC purity = 99.68%
Recycling of the catalyst:
The catalyst was recycled using the process of experiment 2 on 1 mole scale. The results of the recycles are given in Table 3.
Table 3: Recycle study
Sr. No 5% Pd/C
g/mole Hydroxylamine-HCl M/m Temp./time
(°C/hrs) Yield on purity
1 2 g fresh 0.70 80 /2.5 84%
2 1 recycle + 0.2 g 0.70 80 /2.5 81%
3 2 recycle + 0.2 g 0.70 80 /2.5 82%
4 3 recycle + 0.2 g 0.70 80 /2.5 80%
5 4 recycle + 0.2 g 0.70 80 /2.5 88%
6 5 recycle + 0.2 g 0.70 80 /2.5 76%
p-bromophenol: 1 mole, NaOH: 3 mole, water: 1.12 L,
The catalyst used during the preparation of 4’4-biphenol was recycled up-to 5 cycles with no substantial change in the activity of the catalyst.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The process of the present disclosure described herein above has several technical advantages including but not limited to the realization of:
? high yield of 4’4-biphenol;
? high selectivity for 4-bromophenol; and
? simple and economic process of preparation of 4’4-biphenol
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.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments 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 changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:1. A process of preparing 4,4’-Biphenol, said process comprising the following steps:
a. charging an aqueous solution of at least one base and a predetermined amount of p-bromophenol in a reactor to obtain a first mixture;
b. heating said first mixture at a temperature in the range of 50 to 100 °C for a time period in the range of 5 to 60 minutes and allowing it to stand for a predetermined time period to obtain a heated first mixture;
c. adding a predetermined amount of at least one catalyst to said heated first mixture to obtain a second mixture;
d. heating said second mixture at a temperature in the range of 50 to 100 °C to obtain a heated second mixture;
e. introducing a predetermined amount of at least one reducing agent selected from an aqueous solution of hydroxylamine sulfate and an aqueous solution of hydroxylamine hydrochloride to said heated second mixture under inert atmosphere to obtain a third mixture;
f. heating said third mixture at a temperature in the range of 50 to 100 °C for a time period in the range of 30 to 180 minutes to obtain a reaction mass;
g. cooling said reaction mass to a temperature in the range of 30 to 60 °C under inert atmosphere; filtering and washing said reaction mass to obtain a first solid;
h. acidifying said first solid with a mineral acid under inert atmosphere to obtain a slurry;
i. heating said slurry at a temperature in the range of 40 to 70 °C for a time period in the range of 30 to 180 minutes; filtering said slurry to obtain a second solid; and
j. washing said second solid with hot water to obtain 4,4’-Biphenol.
2. The process as claimed in claim 1, wherein the base is at least one selected from a group consisting of NaOH, KOH and NH4OH.
3. The process as claimed in claim 1, wherein said at least one catalyst is palladium supported on carbon.
4. The process as claimed in claim 1, wherein the amount of said at least one catalyst is in the range of 1 mol% to 10 mol% of p-bromophenol.
5. The process as claimed in claim 1, wherein the ratio of the amount of p-bromophenol and the amount the base is in the range of 1:1 to 1:5.
6. The process as claimed in claim 1, wherein the ratio of the amount of p-bromophenol and the amount of at least one reducing agent selected from hydroxylamine sulfate and an aqueous solution of hydroxylamine hydrochloride is in the range of 1:0.1 to 1:1.
7. The process as claimed in claim 1, wherein the ratio of the amount p-bromophenol and the amount of an acid is in the range of 1:0.5 to 1: 1.
8. The process as claimed in claim 1, wherein the acid is at least one selected from a group consisting of H2SO4 and HCl.
9. A process for preparing 4-bromophenol, said process comprising the steps of:
a. charging a fluid medium and phenol in a reactor at a temperature in the range of 0 to 10 °C under stirring to obtain a first mixture;
b. adding a solution of bromine and the fluid medium to said first mixture over a time period in the range of 5 to 8 hours to obtain a second mixture;
c. allowing said second mixture to stand at a temperature of 0 to 10 °C for 1 to 2 hours to obtain a third mixture;
d. adding water to said third mixture and allowing to stand for a time period in the range of 20 to 40 minutes to obtain a biphasic mixture comprising an organic layer and an aqueous layer;
e. separating said organic layer and said aqueous layer of said biphasic mixture and washing said organic layer in a step wise manner with an aqueous sodium thiosulfate and aqueous sodium bicarbonate to obtain an organic solution;
f. concentrating said organic solution to recover ethylene dichloride to obtain an organic concentrate;
g. purifying said organic concentrate by distillation to obtain a purified organic concentrate;
h. crystallizing said purified organic concentrate using a hydrocarbon fluid medium to obtain p-bromophenol.
10. The process as claimed in claim 9, wherein the fluid medium is at least one selected from a group consisting of ethylene dichloride, chloroform and acetonitrile.
11. The process as claimed in claim 9, wherein the ratio of the amount of phenol and bromine is in the range of 1:1 to 1:10.
12. The process as claimed in claim 9, wherein the distillation is carried out over a column packed with ceramic.
13. The process as claimed in claim 9, wherein the distillation is carried out by mixing said organic concentrate with 2,6-di-tert-butyl-p-cresol.
14. The process as claimed in claim 9, wherein the hydrocarbon fluid medium is toluene.