DE696772C - Process for the chlorination or bromination of ketones - Google Patents

Description

Process for the chlorination or bromination of ketones in patent 6g5048 describes a new process to make saturated aliphatic hydrocarbons with three or more carbon atoms into their monochloro or monobromo derivatives without significant formation of higher halogenated 'by-products. The essence of the process is that the vapor of the substance to be halogenated, the halogen through capillaries is blown against, taking care. is that the monohalogenation product at the moment of its formation by condensation from the halogenation zone removed and .due to the further influence of the halogen is withdrawn.

It has now been found that this process is excellent Way also suitable for each one halogen atom in ketones with halogenatable a-position to introduce. Up to now - in the case of the halogenation of ketones, not only one - have to accept a relatively large amount of higher halogenated by-products, In addition, condensation of the ketone often occurred under the influence of the hydrohalic acid formed in the reaction, which further deteriorates the yield resulted in. To prevent this latter circumstance, one has, for example tries to remove the hydrogen halide by adding # 7 of carbonate of lime and to bind water to the ketone to be halogenated. If you can do that too which can prevent unwanted condensation - but so will the benefit achieved bought at the expense of the very laborious work-up and purification of the reaction products. On the other hand, you can probably use the measure just described. Anticipated V condensation prevent the amount of condensation that forms. higher halogenated By-products is not influenced by them.

According to the new procedure, however, both goals are pursued with the same Measure achieved. The substance to be halogenated is in vapor form through a column sent, and occurs, for example, in a vertical reaction space. By a capillary is blown against the vapor, the halogen, with the halogenation occurs immediately. The reaction space is at the boiling point of the to be halogenated Matter held, the higher-boiling Hglogenierungsprodukt condenses and is washed out of the reaction zone by condensate from the starting material. Under these halogenation conditions. finds a condensation only to a very insignificant extent because of the. released hydrogen halide Is boiled away immediately, the capillary blowing in of the halogen to the excess ascending .. Diamp- @ of the starting material causes a- so - r clt ° and perfect D. Mixing of the two reactants that only a slight and technical easily acceptable amount of higher halogenated by-product is formed.

To carry out the process, for example, the one to be halogenated is heated Substance in a bubble for boiling. The steam rises through a column and reaches the reaction space arranged vertically above it from below the rising steam is blown against the halogen through fine capillaries. Complete mixing and halogenation occur at great speed a. The reaction space is at the temperature of the vapor to be halogenated Material held. The halogenation product condenses and becomes from the condensate of the substance to be halogenated in excess, which consists of an over the reflux condenser arranged in the reaction chamber, washed into the column - and thus withdrawn from the effects of further halogen. The hydrogen halide will fed to the absorption. The halogenation is interrupted when almost all of the starting material is present is halogenated and separates the starting material from the halogenation product by distillation.

If circumstances so require, the procedure can also be under pressure or in a vacuum and with or without the use of accelerators. Example z is heated xoo kg of acetone in the apparatus described above for Boil. In the reaction chamber, the rising acetone vapor is blown against the chlorine through capillaries. The chlorination product; Monochloroacetone, gradually accumulates in the boiling vessel at.

The chlorination is interrupted when up to 95 kg of acetone are chlorinated. The excess acetone is then distilled off and the remaining monochloroacetone, which contains 3 to 5% dichloroacetone, is purified by vacuum distillation. The yield is 95 % of theory. However, if one of the claimed measures, for example the capillary supply of the chlorine, is omitted and the chlorine is introduced into the reaction chamber under otherwise the same circumstances through a pipe which can no longer be addressed as capillary compared to the reaction cross-section, the amount of im crude chloroacetone contained dichloroacetone to about 15 0/0.

Example a 72 kg of methyl ethyl ketone are heated to the boil in a similar way to Example = and chlorine is blown against the vapor rising through a column into the reaction chamber through a capillary. The process is interrupted when about 0/0 of the ketone are chlorinated. The unchanged methyl ethyl ketone is then first distilled off and the remaining mixture of chlorination products is fractionated. 50/0 monochlorides are obtained, while the remainder is more highly chlorinated. - 9.6 % of the monochlorides consist of chloromethyl ethyl ketone, 7q.0% are methyl chloroethyl ketone.

Example 3 xa, o kg of acetone phenone are produced using a similar procedure as in example = subjected to bromination, with the rising acetophenone vapor through a capillary. Bromine is counterblown in vapor form. If g kg of the product are brominated, the unchanged starting material is distilled off in vacuo. That remaining crude co-bromoacetophenone, which accrues with 940 /, the theory and about 5 0/0 dibromoacetophenone can be purified by recrystallization.

Claims (1)

PATENT CLAIM: Process for the chlorination or bromination of ketones with halogenatable a-position in the vapor phase at one temperature; in which the reaction products are removed from the reaction zone by condensation at the moment they are formed, characterized in that the chlorine or bromine is blown against the vapor through capillaries.