DE686849C - Process for the preparation of haloalkylenes and organic acids from alkyl esters of aliphatic or aromatic acids - Google Patents

Description

Process for the preparation of haloalkylenes and organic acids from alkyl esters of aliphatic or aromatic acids It is known that React alkyl esters of aliphatic or aromatic acids with hydrogen halide allow to halogen alkyls and the corresponding acids according to the reaction scheme: RCOOR '+ HX - RCOOH +. R'H, where R is an alkyl or aryl radical, R 'is an all: yl radical and X is halogen. These conversions are relatively slow, especially those with hydrogen chloride. It has therefore already been proposed for the purpose of accelerating the reaction the ester to be cleaved in the presence of catalysts in the liquid phase with hydrogen halide to be treated at higher temperatures until the cleavage is carried out. This mode of operation is discontinuous and requires the cumbersome one each time Separation of the catalyst from the liquid. It has now been found that one can carry out the implementation continuously and surprisingly easily in such a way that that one undecomposed, distillable esters in vapor form in a mixture with hydrogen halide via suitable contact materials. The material question arises with this one The way of working is much easier than when working in the liquid phase.

Surface-active substances such as charcoal, pumice stone, Fuller's earth, aluminum oxide and diatomaceous earth, among others. used, their activity through metal salts can be increased.

Instead of hydrogen halide, however, can also be used in the reaction those compounds are introduced that are among those decisive for the transesterification Reaction conditions (elevated temperature, presence of contact substances) slightly hydrogen halide split off, e.g. B. tetrachloroethane, pentachloroethane and others.

However, it is expedient to eliminate hydrogen halide Halocarbons and the transesterification not to be carried out in one operation, but to work in two stages. So you first split according to known methods from halogenated hydrocarbons, e.g. B. tetrachloroethane, hydrogen halide, separates this from the other cleavage component and then uses it for the one described above Transesterification. You already have haloalkyls from carboxylic acid esters produced in 'liquid phase. Before this mode of operation, however, has the in the Vapor phase working methods according to the invention have the following advantages: i. The speed of implementation in the case of the carboxylic acid esters, which distill without decomposition, work is in the vapor phase much higher than when working in the liquid phase, since in the latter case straight in the case of the low-boiling esters, the reaction temperatures are too low have to.

2. The laborious separation of the catalyst from the reaction mixture not applicable when working in the vapor phase.

3. Since you are working in the vapor phase above the dew point of aqueous hydrochloric acid is located, the implementation of the process does not present any material difficulties, while in the liquid phase, corrosion is difficult when working with hydrogen chloride is avoidable, since small amounts of water are always available.

Examples i. A mixture of 0.6 mol of ethyl acetate and 0.5 is passed Moles of hydrogen chloride every hour at 27o ° over about 25o ccm of zinc chloride as contact. The reaction gases are condensed, and continuously chloroethyl in the reflux condenser and boiled small amounts of hydrogen chloride. The one made from glacial acetic acid and excess Ethyl acetate existing condensate is separated by fractional distillation. The chloroethyl is washed neutral, dried and condensed.

2. A vaporous mixture of 0.5 moles of tetrachloroethane and 0.5 moles of ethyl acetate is passed every hour over about zoo cc of aluminum hydroxide contact with 211 ° copper at temperatures of 300 to 32o °. Ethyl chloride and hydrogen chloride are removed from the condensed reaction components by flasks under reflux; the chloroethyl is washed neutral, dried and condensed. The condensate, which consists of trichlorethylene, acetic acid and unreacted tetrachloroethane and ethyl acetate, is broken down by fractional distillation. The unreacted starting materials, tetrachloroethane and ethyl acetate are fed back into the reaction. 3. It is split off from tetrachloroethane over activated charcoal as a contact at about 300 ° hydrogen chloride and separates this from the trichlorethylene. Trichlorethylene is distilled after the Tetraf- small amounts of undecomposed Tetra-'chi.oräthans with lime to the pure product.

The split off hydrogen chloride is treated with ethyl acetate at about 2oo ° Via chlorine zinc kieselguhr contact to ethyl chlorine and glacial acetic acid in that described in Example i Wise implemented.

4. For the purpose of obtaining ethyl chlorine and propionic acid from ethyl propionate and hydrogen chloride is passed a mixture of 0.5 g mol per hour of the starting materials at zio to 22o ° over 25o ccm of a contact, which is made up of grains and Diatomaceous earth impregnated with zinc chloride consists. Working up the reaction products takes place as indicated in example i.

5. A mixture of methyl formate vapor and hydrogen chloride is passed through at 24o to 2: 5o ° over the. contact given in example 4, mam receives in good yield chloromethyl and formic acid.

6. A mixture of methyl benzoate and hydrogen chloride is passed through at 27o to 2 $ 0 ° over the contact used in Example 4, a good one is obtained Yield chloromethyl and benzoic acid.

Claims (1)

PATENT CLAIMS: i. Process for the preparation of haloalkylenes and organic acids from alkyl esters of aliphatic or aromatic acids, thereby characterized in that -man aliphatic or aliphatic or undecomposed distillable alkyl esters aromatic acids and hydrogen halide at higher temperatures and ordinary or elevated pressure in vapor form via surface-active contact substances, their activity can be increased by metal salts, such as charcoal, pumice stone, fuller's earth and aluminum oxide, brings to implementation. 2 @ method according to claim i, characterized in that compounds which split off hydrogen halide are used instead of hydrogen halide brings to implementation.