4-Bromo-o-xylene

Chemical Properties

Clear colourless to light yellow liquid

Uses

4-Bromo-o-xylene is used as synthetic organic materials and soluble polyimide resin intermediates.

Synthesis

A method for the preparation of 4-bromo-1,2-xylene, the method uses o-xylene as raw material, in the presence of dichloromethane solvent and catalyst, dropwise addition of bromine at a temperature of -60 to -20 , o-xylene and bromine molar ratio of 1:1, after the dropwise addition is completed, hold the temperature to carry out the reaction, and then slowly raise the temperature to 10-20 , to remove the dissolved hydrogen bromide in the reaction solution, add saturated aqueous solution of sodium sulfite , stirring for 30 minutes, the product containing dichloromethane was recovered by layering, and then washed with 5% dilute alkali solution to PH = 8-9, and finally washed with water to neutral, to obtain colorless or light yellow 4-bromo-1,2-xylene crude product, distillation under atmospheric pressure to recover solvent dichloromethane, and then distillation under reduced pressure to obtain 4-bromo-1,2-xylene product, said catalyst is a mixture of ferric chloride and quaternary ammonium salt, and the catalyst is a mixture of ferric chloride and quaternary ammonium salt. The quaternary ammonium salt is for example: tetrabutyl ammonium chloride, tetrabutyl ammonium bromide, tetrapropyl ammonium bromide, methyltrioctyl ammonium chloride, benzyltriethylammonium chloride, and the mass ratio of ferric trichloride and the quaternary ammonium salt is 4-5:1. The content of the obtained 4-bromo-1,2-xylene is increased to 85-93%, and at the same time, the content of the byproduct is reduced, and the yield of the product is increased to 95%. Duration of bromine addition: 3-4 h. Holding time of reaction: 2 h. Temperature of alkaline washing: room temperature.