DE1134362B - Process for the preparation of ªÏ-bromoalkanes - Google Patents

Description

It is known to make aliphatic bromides by reaction certain terminal olefins with a large excess of liquid hydrogen bromide in the presence of a high concentration of a peroxide catalyst. These processes are large-scale as a result the high consumption of expensive peroxide catalyst, the large amounts of hydrogen bromide required and not feasible due to the low rate of formation of the bromide product.

It has also been proposed to implement it of olefins with hydrogen bromide under the influence of silent electrical discharges. Here, however, relatively more hydrogen bromide is consumed than is necessary according to the invention is. According to another proposal, olefins are treated with hydrogen bromide under the influence of ultraviolet light implemented. However, the yields in this process are relatively modest.

It has now been found that ω-bromoalkanes by reacting -olefins with hydrogen bromide, in the presence of peroxide catalysts, and in the presence of the <w-bromoalkane obtained as the end product as a solvent, can be produced in that 1-butene or 3-chlorobutene-1 and gaseous hydrogen bromide continuously in a molar ratio of 0.8: 1 to 1.2: 1 and in the presence of 0.25 to 1 percent by weight Peroxide, based on the reaction mixture, are implemented.

The method according to the invention is based on the discovery that a very high rate of formation of the aliphatic bromide can be achieved and the consumption of expensive peroxide catalyst is reduced to a negligible value.

The reaction is carried out under such conditions that the molar proportion of hydrogen bromide in Solution is not significantly higher than that of the olefin. The molar ratio of olefin to used Hydrogen bromide is at least about 0.8: 1, preferably at least 1: 1, and can be up to 1.2: 1.

Any suitable peroxide can be used to catalyze the reaction, e.g. B. benzoyl peroxide, di-tert-butyl peroxide and ascaridol. The concentration of the peroxide used is at least 0.25 percent by weight, based on the reaction mixture. Using a higher concentration of peroxide than about 1 percent by weight of the reaction mixture is of no advantage.

The reaction can be carried out at any suitable temperature, e.g. B. between -20 and + 3O ⁰ C, preferably between 0 and 30 ° C. The best method of making
of ω-bromoalkanes

Applicant:

The Distillers Company Limited,
Epsom, Surrey (UK)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald

and Dr.-Ing. Th. Meyer, patent attorneys,

Kölnl, Deichmannhaus

Claimed priority:
Great Britain 9 April 1958 (No. 11 291)

Edward James Gasson, Epsom Downs, Surrey

(Great Britain),
has been named as the inventor

However, the temperature differs depending on the peroxide catalyst used. With benzoyl peroxide it has been found that temperatures above about 30 ° C are disadvantageous because they promote the formation of secondary Favor bromides.

The reaction according to the invention is carried out in the liquid phase. According to one embodiment gaseous hydrogen bromide is continuously converted into a solution of the olefin and a peroxide catalyst in the formed aliphatic bromide serving as a solvent for the reaction introduced. Optionally, additional solvents or diluents can be present. In a preferred Embodiment is gaseous hydrogen bromide, the olefinic starting material and a Solution of peroxide in the aliphatic bromide formed continuously in the from a solution of the Olefins existing in the aliphatic bromide formed and in one with an overflow device filled container containing liquid reaction mixture. The hydrogen bromide, which is used as a starting material olefin used and the peroxide catalyst are introduced separately at the bottom of the reaction vessel, while the aliphatic

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Bromide, in the dissolved peroxide, and slight. _{Amounts of} dissolved olefin contained, overflows at the top of the container.

The aliphatic ^ bromide can, if necessary, purified for example by fractional distillation will. In a preferred embodiment, a substantial part of the aliphatic bromide is through Flash distillation separated from the reaction product. What remains is a concentrated solution of peroxide in the aliphatic bromide, which is returned to the reaction vessel.

The normal aliphatic bromides prepared by the process according to the invention can e.g. B. used for the production of normal alcohols.

example 1

A butene mixture (91.7% butene-1 and 8.3% butene-2) and gaseous, anhydrous hydrogen bromide were separated, via gas distributors, in the lower end of a cylindrical, with a water jacket introduced reactor which contained n-butyl bromide and was kept at 20 ° C. Simultaneously a 5% solution of benzoyl peroxide in n-butyl bromide was introduced in cocurrent with the gases. The amounts used per hour and liter of reactor space were as follows: 3751 butene, 3501 Hydrogen bromide, 17 g benzoyl peroxide. The butyl bromides formed were continuously using a Overflow device withdrawn from the reactor.

Analyzes carried out after an operating time of 2 hours showed that no hydrogen bromide was present in the outlet gas and that the liquid product was only a trace of free hydrogen bromide corresponding to 0.2% of the amount used Amount contained. The yield of n-butyl bromide based on the 1-butene consumed was 91%, and the yield of mixed n- and secondary butyl bromides based on the mixed used Butenes, amounted to 99% Only 2.4% of the benzoyl peroxide used was consumed in the process, i.e. the peroxide consumption per 100 parts of n-butyl bromide formed was only 0.02 part.

The residual peroxide was concentrated to about 5% by the reaction product was passed through a working at 120 ⁰ C and atmospheric pressure evaporator.

Example 2

This example illustrates the high reaction rates that can be achieved.

In the reactor described in Example 1 13001 butene-1, hydrogen bromide and 1.31 13001 5% Benzoylperoxydlösung in n-butyl bromide were passed at 2O ⁰ C, per liter of reactor volume is introduced. The outlet gas was free from hydrogen bromide and the liquid product contained only traces of hydrogen bromide in an amount of 0.01% of the hydrogen bromide used.

Example 3

601 gaseous hydrogen bromide and 551 butene-1 were introduced into a maintained by external cooling at 2O ⁰ C stirred tank per hour per liter of reactor space containing a 2% solution of di-tert-butyl peroxide in a mixture of n-butylbromide and secondary butyl bromide. All of the butene was consumed and the excess hydrogen bromide was separated off in a washing tower. After an operating time of 45 minutes, the product was analyzed. The yield of n-butyl bromide, based on the 1-butene used, was 95.9%, and the peroxide consumption was 1 part per 100 parts by weight of n-butyl bromide formed.

For comparison with the previous examples, the following batch test was carried out:

20 g of 1-butene, 78 g of liquid hydrogen bromide and 1 g of benzoyl peroxide were placed in an enamelled pressure vessel at -7O ^{0 C.} The container was sealed and mechanically shaken. During this, it was allowed to warm to room temperature (about 20 ° C.). After 17 hours the container was opened and the contents analyzed. No peroxide remained and the yield of n-butyl bromide, based on butene-1, was only 76%. The peroxide consumption was 3.3 parts per 100 parts by weight of n-butyl bromide formed. It can be seen that in this case the yield of n-butyl bromide was relatively low and the consumption of peroxide was relatively high.

Claims (3)

PATENT CLAIMS: 1. A process for the preparation of co-bromoalkanes by reacting -olefins with hydrogen bromide, in the presence of peroxide catalysts and in the presence of the ω-bromoalkane obtained as the end product as a solvent, characterized in that butene-1 or 3-chlorobutene-l and gaseous Hydrogen bromide can be reacted continuously in a molar ratio of 0.8: 1 to 1.2: 1 and in the presence of 0.25 to 1 percent by weight of peroxide, based on the reaction mixture. 2. The method according to claim 1, characterized in that that the process is carried out at temperatures between 0 and 30.degree. 3. The method according to claims 1 and 2, characterized in that the after the separation of the formed ω-bromoalkane remaining concentrated solution of the peroxide catalyst is returned to the reaction zone. Considered publications:
German Patent No. 846 692;
■ British Patent No. 554 499;
U.S. Patent No. 2,540,127;
Chemical Reviews, 27 (1940), pp. 351 to 412, especially pp. 379, 380. © 209 629/276 7.62