Title of Invention	A PROCESS FOR THE SYNTHESIS OF 4, 4' -DIHALOBENZOPHENONES
Abstract	This invention relates to a process for the synsthesis 4,4'-dihalobenzophenone. Halobenzene is reacted with carbon tetrachloride in the presence of anhydrous aluminum chloride as a catalyst. The reaction is then steam distilled and the product separated and crystallised from the aqueous layer.

Full Text

This invention relates to a process for the synthesis of 4,4'-dihalobenzophenone- 4,4'-dihalobenzophenone is used in the production of aromatic polyketone polymers having phenylene groups, oxygen atoms and ketone groups in their molecular chain. For example 4,4'-difluorobenzophenone is condensed with di(alkali metal) salts of aromatic bisphenols to form polyketones. Alternately 4,4'-difluorobenzophenone is condensed with aromatic bisphenols in the presence of alkali metal carbonates or bicarbonates to form polyketones- Hitherto known processes of synthesising 4,4'dihalobenzenes are not satisfactory due to many reasons. In one such method, halobenzene is reacted with P- halobenzoylchloride or phosgene. The reac tion wi th phosgene produces isomeric mi x tures which require further purification- The reac tan t p-^halo-benzoy 1 chloride used in the other process is very expensive* As such both the above referenced processes for synthesising 4,4-dihalobenzophenones are not commerc ially acceptable,. Yet another process for synthesis of 4,4'-dihalobenzophenone is by the diazot ization of 4,4'*-diaminodiphenyl methane in anhydrous or concentrated aqueous hydrogen fluoride. Diazonium fluoride thus produced is subsequently decomposed in the presence of nitrous acid or nitrite ions- The product yield of this process depends on the concentration of HF. It is obvious that handling of concentrated HF poses problems in view of its high toxicity and corrosive nature. Further, the other reactant 4,4'-diaminodipheny1 methane is carcinogenous and large scale handling is a health hazard- The present invention is aimed at developing a cheaper, easily operable and safe process for synthesising 4,4-dihalobenzophenones, Yet another object is to avoid production of isomers which requires further purification steps. Our investigation and research resulted in developing a simple process for the production of 4,4'-diohalobenzophenones in very good yield. The reactants involved in our process are cheaper and are readily available. Bulk handling for cornmercial production is also possible as these reactants BrB relatively safe and do not posses carcinogenic properties- Further the process affords recyclinq of the unreacted components to the reaction system, thereby minimising production loss - The process for the synthesis of 4,4'-dihalobenzophenone according to this invention comprises the steps of reacting halobenzene with carbon tetrachloride in the presence of anhydrous Aluminum Chloride as a catalyst, steam distil 1ing said reaction mixture to remove unreacted reagents therefrom and separating 4,4'-dihalobenzophenone from the aqueous layer of said reaction mixture by known methods. Halobenzene reactant may be fluorobenzene, chlorobenzene or bromobenzene. The molar ratio of halobenzenes to carbon tetrachloride may vary from 2:4 to 2s7 and the reaction temperature may be in the range of 5 to 25^C. Reaction time may vary from 5 to 15 hours and the duration of steam distillation may be from 16 to 24 hours- The product can be separated from the reaction mixture by crystallization. Further purification may be effected by recrystallization from an organic solvent such as hexane, methanol or a mixture of the two in the presence of activated cation - The invention will now be described with reference to the following examples which arB only illustrative and non 1imitive. Example 1 Synthesis of 4,4'-difluorobenzophenone from fluorobenzene and carbontetrachloride in the molar ratio of 2:5. 180g of anhydrous aluminum chloride (1.35 mole) and 300ml of CCl^ (3.108 mole) were added into a 3 necked round bottom flask of 3 litre capacity fitted with stirrer and thermowel1 while maintaining the temperature between 10-15°C using an immersion cooler with acetone bath. After 15 minutes of stirring 26,16 ml of fluorobenzene About 900 ml disti1 led water was added to the reaction mixture drop by drop with stirring maintaining the temperature between 5-10^C« The reaction mixture was allowed to warm to room temperature after the addition was completed. Excess CCl^ was distil led off from the product by simple distillation on a water bath and then the reaction mixture was steam disti1 led for about 20 hours to remove the residual CCl^ and fluorobenzene and to hydrolyze the intermediate product. The aqueous layer was decanted and the light yellow solid was separated. The product was recrystal1ized from an 0.75g of activated charcoal and 1500 ml hexane mixture to yield lOlg (46*/.) white crystal line product of 4,4'-difluorobenzophenone; melting point 107°C- The structure of the product was confirmed by infra-red and nuclear magnetic resonance spectroscopy. Example 2 Synthesis of 4,4'-dichlorobenzophenone from chlorobenzene and carbon tetrachloride in the molar ratio of 2:5. 180g of anhydrous aluminum chloride (1.35 mole) and 300ml of CCl^ (3.108 mole) were added into a 3 necked round bottom f1 ask of 3 1itre capacity fitted with stirrer and thermowel1 while maintaining the temperature between 10-15^C using an immersion cooler with acetone bath. After 15 minutes of stirring 26*26 ml of chlorobenzene (0.278 mole) was added drop by drop through separatory funnel in about 10 minutes maintaining the temperature between lO^-lS^^C. The reaction commenced immediately and a mixture of 175.90 ml chlorobenzene (1.73 mole) and 180 ml CCl ^^ (1.865 mole) was added drop by drop using separatory funnel in about 2 hours maintaining the temperature between 5 and 10°C- Stirring was continued for a further period of 3 hours maintaining the temperature between 5-10°C and the reaction mixture was allowed to stand overnight at room temperature- About 900 ml distilled water was added to the reaction mixture drop by drop with stirring maintaining the temperature between 5-10°C, The reaction mixture was allowed to warm to room temperature after the addition was completed. Excess CCl^ was distilled off from the product by simple distillation on a water bath and then the reaction mixture was steam distilled for about 20 hours to remove the residual CCl^ and chloroben^ene and to hydrolyzB the intermediate products The aqueous layer was decanted and the light yellow solid was separated. The product was recrystal1ized from an 0.75g of activated charcoal and 1500 ml hexane mixture to yield 106g (A2'/,) white crystal 1ine product of 4,4'-dichlorobenzophenone; melting point 145° C. The structure of the product was confirnmed by infra-red and nuclear magnetic resonance spectroscopy. Obvious equivalents known to persons skilled in the art are not excluded from the scope of the appended claims. WE CLAIMS 1- A process for the synthesis of 4,4'-dihalobenzophenone comprising the steps of reacting halobenzene with carbontetrachloride in the presence of anhydrous aluminum chloride as a catalyst, steam distilling said reaction mixture to remove unreacted reagents therefrom, and separating 4,4'-dihalobenzophenone from the aqueous layer of said reaction mixture by known methods. 2. The process as claimed in claim 1, wherein said halobenzene is selected from fluorobenzene, chlorobenzene or bromobenzene. 3. The process as claimed in claim 1 and 2, wherein said 4,4'-dihalobenzophenone is separated from the aqueous reaction mixture by crystallization- 4. The process as claimed in claim 3, wherein said crystals of 4,4'-dihalobenzophenone are purified by recrystal1ization from hexane, methanol or mixture of the two in the presence of activated charcoal. 5. The process as claimed in any of the preceding claims wherein halobenzene to carbon tetrachloride ratio is from 2:4 to 2:7. ^ ■ The process as claimed in any of the preceding claims wherein the reaction temperature is between 5 to 25^C. 7- The process as claimed in claims 1-6, wherein said reaction between halobenzene and carbon tetrachloride is allowed to proceed from 5 to 12 hours. 8. The process as claimed in claims 1-7, wherein said steam distillation is effected for a period of 20 hours. 9. A process for the synthesis of 4,4'-dihalobenzophenone substantially as herein described and exemplified.

Documents:

286-mas-2000-abstract.pdf

286-mas-2000-claims filed.pdf

286-mas-2000-claims granted.pdf

286-mas-2000-correspondnece-others.pdf

286-mas-2000-correspondnece-po.pdf

286-mas-2000-description(complete)filed.pdf

286-mas-2000-description(complete)granted.pdf

286-mas-2000-form 1.pdf

286-mas-2000-form 19.pdf

286-mas-2000-form 26.pdf

286-mas-2000-form 3.pdf