DE2204194C3 - Process for the preparation of allyl bromide - Google Patents

Description

Allyl halides, in particular allyl chloride and Aüylbromid, are products that are used on a large scale Manufacture of various drugs, pesticides and similar compounds Compounds can be used as starting materials. In addition, Ällylbromid is used on various occasions used as a fumigant for soil disinfection.

As is known, allyl bromide (3-bromopropene-1) can by reacting allyl alcohol with potassium bromide and concentrated sulfuric acid or with Phosphorus tribromide can be obtained. Furthermore, a method is known, after the allyl alcohol in The presence of catalysts is reacted with hydrogen bromide.

The starting product for the processes mentioned is always allyl alcohol, which in turn is alkaline Hydrolysis of allyl chloride is obtained on an industrial scale. Therefore, a method was sought which allows allyl bromide to be produced directly from allyl chloride. It is also known, Ällylbromid by reacting allyl chloride with sodium or calcium bromide in aqueous solution to convert, see Houben-Weyl, "Methods of Organic Chemistry", V / 4 (1960) 354.

There has now been a process for the preparation of allyl bromide by rehalogenation of allyl chloride found, dos is characterized in that one allyl chloride in the presence of 0.001 to 1.0 mole of an inorganic halide per mole of allyl chloride as a catalyst with aqueous hydrobromic acid, 1 to 2 moles of hydrogen bromide per mole of allyl chloride are used.

To carry out the process according to the invention, an aqueous solution that is in a suitable reaction vessel and an inorganic halide, preferably copper halide, in particular copper chloride, copper bromide or a mixture of these two copper compounds, as well as Contains hydrogen bromide, added allyl chloride. The submitted aqueous hydrogen bromide solution should preferably be 48 to 66 percent by weight, preferably 62 percent by weight, contain HBr. The allyl chloride should be added slowly and gradually to the mixture small portions are added, the reaction mixture being mixed vigorously. Same-

xo early the mixture to the reaction temperature brought and for the time of the addition of allyl chloride and the duration of a post-reaction at this temperature held. The reaction temperature can be between room temperature and the boiling point of the reaction mixture. After completion of the reaction and agitation of the reactive mixture the reaction mixture separates into a lower, anhydrous phase, which consists of the AHyl bromide and from unreacted So lylchlorid is formed, and an upper, aqueous Phase containing the hydrogen chloride formed as a by-product and, if applicable, the excess Contains hydrogen bromide and the catalyst. The aqueous phase can, for example after the

Processes that are described in laid-open specifications 1 567 427 and 1 567 428 are worked up. However, it is also possible to use the aqueous solution originally containing HCl and HBr, if their HCl content is not too high, they can be used again directly for a new batch.

The anhydrous phase is worked up by distillation, the more volatile, unreacted Allyl chloride passes over first and can be recovered for a new reaction while

the less volatile allyl bromide is in the distillation flask enriches. In this way, a yield based on converted allyl chloride of 90% of theory achieved, the degree of conversion of the allyl chloride being about 6O%.

According to the process of the invention, it is possible to use allyl chloride in a technically simple manner Process sequence to implement directly to allyl bromide in high yield with hydrogen bromide.

example

In one with heating, stirrer and dropping funnel equipped reaction vessel are given 1080 parts by weight of an aqueous solution in the 648 parts by weight of hydrogen bromide and 13 parts by weight of copper bromide are dissolved. While the solution warmed to 25 ° C and this temperature is still maintained, are via the dropping funnel 306 parts by weight in the course of IV2 hours Allyl chloride was added dropwise, the reaction mixture being stirred vigorously. After the addition of the allyl chloride becomes the contents of the reaction vessel while maintaining the temperature stirred from 25 ° C for a further 6 hours and then

the stirrer switched off. The reaction mixture then separates into a lower, anhydrous one and upper, water-containing layer. The upper layer, which consists essentially of HCl, HBr and CuBn exists in aqueous solution, is sucked off,

so that only the anhydrous layer remains in the reaction vessel. After the dropping funnel against a distillation head with a cooler has been replaced, the contents of the reaction vessel

ßes, which essentially consists of the allyl bromide formed and the unreacted allyldilond, heated to the Seden. Here is in the main Allyl chloride in addition to small amounts of allyl bromide overdone. After the boiling temperature has risen to 67 ° C, the distillation is stopped. There are then 286 parts by weight in the piston Allyl bromide in a purity of about 85 percent by weight, which is obtained by distillation ι a purity of over 99% can be achieved.

Claims (3)

"t® patent claims: "" I 1. Process for the preparation of allyl bromide by Umhalqgenierung of allyl chloride, characterized in that one AUyI- Z chloride in the presence of 0.001 to 1.0 mole of an inorganic halide per mole of allyl chloride as a catalyst with aqueous hydrobromic acid, 1 to 2 moles of hydrogen bromide being used per mole of allyl chloride 2. The method according to claim 1, characterized in that an aqueous hydrobromic acid with an HBr content of 48 to 66 percent by weight, preferably 62 percent by weight, is used. 3. The method according to claims 1 and 2, characterized in that the implementation at a temperature between room temperature and the boiling point of the reaction mixture is carried out.