Sodium Hydroxide → 1,2,4-Tribromo-5-ethenylbenzene

Temperature

35 °C

105.5 g β-bromoethyl tribromobenzene (as above) (0.25 mol), 1 g triethylbutyl ammonium bromide (as 50% aq.solution) 50 g isopropyl alcohol and 1 g sodium nitrite were stirred at about 500 rpm. in a 1 liter three-necked flask at room temperature. 55.6 g 45% NaOH solution (0.625 mol) were added slowly such that the reaction exotherm gradually raised the temperature to 35° C. When necessary an ice-water bath was raised under the flask to control the temperature. After about 5 minutes of reaction, tribromostyrene started to precipitate from the solution. The stirring was continued for a total of 45 mins. At the end of this period the reaction mixture was filtered using a water vacuum pump. The solid remaining in the funnel was tribromostyrene. The filtered liquid consisted of three separate phases--an aqueous mixture of sodium bromide and hydroxide, an isopropanol phase and a small dark layer containing the heavies. The tribromostyrene was dissolved in n-hexane (approx 150 g), washed with dilute HCl and water and dried over calcium chloride. After filtering off the calcium chloride, the hexane was removed under vacuum at 40° C. until the first crystals appeared. The hexane solution was allowed to cool slowly to room temperature and then in an ice-water bath. The crystals were filtered off, and dried overnight in a vacuum oven at 40° C. 62 g 2,4,5-tribromostyrene were obtained (m.p=64° C.). In the mother liquor (hexane) were dissolved approx. 12 g of products consisting of a mixture of tribromo and tetrabromostyrenes. The isopropanol phase contained about 8 g of product mixtures including dibromostyrene.

1. customat room temperature
2. temperatureWhen necessary an ice-water bath was raised under the flask
3. customto precipitate from the solution
4. customwas continued for a total of 45 mins
5. filtrationAt the end of this period the reaction mixture was filtered
6. customseparate phases
7. additionan aqueous mixture of sodium bromide and hydroxide
8. additionan isopropanol phase and a small dark layer containing the heavies
9. dissolutionThe tribromostyrene was dissolved in n-hexane (approx 150 g)
10. washwashed with dilute HCl and water
11. dry with materialdried over calcium chloride
12. filtrationAfter filtering off the calcium chloride
13. customthe hexane was removed under vacuum at 40° C. until the first crystals
14. temperatureto cool slowly to room temperature
15. filtrationThe crystals were filtered off
16. customdried overnight in a vacuum oven at 40° C

ORD record

ord-cc0c2b2797d34ddfb3a9c7fe82a03c96

Source dataset

uspto-grants-1988_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04748286