Claims
- 1. A regioselective process for producing an isomer mixture comprising 3-bromo- and 4-bromo-o-xylene wherein said isomer mixture is rich in 4-bromo-o-xylene which process comprises combining bromine with o-xylene in a reaction zone within a bromine to o-xylene mole ratio range of more than about 1:1 to about 2:1, respectively, while maintaining the resulting admixture at a temperature in the range of about -20.degree. C. to about 40.degree. C. to produce a product mixture.
- 2. The process of claim 1 wherein said reaction zone is shielded from actinic radiation.
- 3. The process of claim 1 wherein said combining is conducted in a liquid sulfur dioxide medium.
- 4. The process of claim 3 wherein said sulfur dioxide is present in an amount such that the mole ratio of sulfur dioxide to o-xylene is at least about 1:1.
- 5. The process of claim 3 wherein said sulfur dioxide is present in an amount such that the mole ratio of sulfur dioxide to o-xylene is in the range of about 2:1 to about 30:1.
- 6. The process of claim 3 wherein said sulfur dioxide is present in an amount such that the mole ratio of sulfur dioxide to o-xylene is in the range of about 5.2:1 to about 23.5:1.
- 7. The process of claim 1 wherein said combining is carried out in the presence of a Lewis acid catalyst.
- 8. The process of claim 1 wherein said mole ratio of said bromine to said o-xylene is about 1.1:1 to about 1.5:1.
- 9. The process of claim 1 wherein said mole ratio is about 1.5:1.
- 10. The process of claim 1 wherein said combining is accomplished by gradually adding said bromine with stirring to said o-xylene at an addition rate in the range of about 0.5 to about 1.5 moles of bromine per hour per mole of o-xylene to produce said admixture.
- 11. The process of claim 10 wherein, after said combining is completed, the resulting admixture is agitated for a time period in the range of about 0.05 to about 4.5 hours.
- 12. The process of claim 10 wherein said o-xylene is first dissolved in sulfur dioxide prior to said combining, and wherein said sulfur dioxide is present in a mole ratio of said sulfur dioxide to said o-xylene of at least about 1:1, and wherein said admixture is agitated for a period of time of about 0.05 to about 0.5 hour to produce a product mixture.
- 13. The process of claim 1 further comprising subjecting said product mixture to vacuum distillation to isolate said isomer mixture.
- 14. The process of claim 1 wherein said temperature is in the range of about -9.degree. C. to about -15.degree. C. and said bromine is added to said o-xylene.
- 15. The process of claim 3 wherein said sulfur dioxide is maintained at its reflux temperature during said combining.
- 16. The process of claim 3 wherein the resulting admixture is maintained at a temperature of about -15.degree. C.
- 17. The process of claim 3 wherein said admixture is maintained under autogenous pressure at a temperature above about -9.degree. C.
- 18. The process of claim 12 wherein said product mixture is warmed to an extent sufficient to evaporate said sulfur dioxide and produce a liquid reaction product.
- 19. The process of claim 18 wherein said liquid reaction product is subjected to vacuum distillation to isolate said isomer mixture.
- 20. The process of claim 1 wherein said isomer mixture is passed through a capillary gas chromatography column which has been precoated with cyanopropyl methyl silicone to separate 4-bromo-o-xylene from at least 3-bromo-o-xylene.
Parent Case Info
This is a continuation-in-part application of application Ser. No. 484,353 filed on Feb. 22, 1990, U.S. Pat. No. 5,026,932.
US Referenced Citations (5)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
484353 |
Feb 1990 |
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