DE1133710B - Process for the production of ª ‡, ª ‡ -Dichloropropionic acid - Google Patents

Description

Process for the preparation of a, a-dichloropropionic acid It is known x, x-dichloropropionic acid by chlorination of propionic acid or x-chloropropionic acid to be prepared in the presence of phosphorus or phosphorus compounds (see US Pat 2 809 992). A disadvantage of this process is that the chlorination form insoluble phosphorus-containing, resin-like products in the reaction mixture which heavily soiling the chlorination equipment. With discontinuous chlorination the chlorination boiler must be laborious and time-consuming after each batch getting cleaned; If chlorination is carried out continuously, the chlorination must be very frequent interrupted in order to remove viscous deposits from the apparatus. Even during the distillation of the crude x, x-dichloropropionic acid, these resinous ones prepare Arrears difficulties.

It has been found that one avoids this disadvantage when one as Catalyst a compound of the general formula R1 (R2) N -S (X) 02 in the R1 and R2 is hydrogen or identical or different, optionally substituted alkyl or aryl radicals and X is a hydroxyl or alkoxy radical or a halogen atom, used. Substituted alkyl or aryl radicals include, for example, chloromethyl, Understand chloroethyl or chlorophenyl radicals.

It has been shown that these compounds have good catalytic properties Effect on aie chlorination of propionic acid or x-chloropropionic acid to, .Dichloropropionic acid and that when you use them you get a clear, insoluble resinous by-product free reaction mixture is obtained, so that the equipment is clean during operation stay.

Also in the distillation of the crude chlorination mixture obtained in this way In contrast to the known procedure, it remains in the presence of phosphorus or phosphorus compounds a thin residue that can be easily removed from the still leaves and does not require any special cleaning of the apparatus.

The catalytically active compounds to be used according to the invention belong e.g. B. the amidosulfonic acid H2N - SO3H, its chloride HN-SO2Cl, its ester, e.g. H2N-SO2OCH3, or Ethylaminosulfochlorid C2H5NH - SO2Cl.

You can use these catalysts of the carboxylic acid to be chlorinated directly add, but you can also during the chlorination, d. H. so »in situ«, by adding the carboxylic acid bonds that make up this Catalysts arise. So you can z. B. instead of ethylaminosulfonyl chloride add its starting substances monoethylamine and sulfuryl chloride.

One of the easiest and most accessible catalytic effective compounds is the sulfamic acid. An addition of z. B. 3 to 5 ° / 0 Amidosulfonic acid is sufficient for the α-chloropropionic acid or propionic acid to be chlorinated, to achieve a sufficient catalytic effect. Assuming a-chloropropionic acid off, it is expedient to chlorinate at a temperature of 170 to 175 ° C. If one goes from propionic acid, it is expedient to first chlorinate at about 120 ° C. until the Propionic acid is converted to z-chloropropionic acid, and then increases the temperature up to 170 to 175 "C.

To prevent undesirable occurrence, in the chlorination liquid insoluble by-products and, above all, the formation of a thin-bodied residue to achieve in the distillation of the crude chlorination mixture, it is appropriate to if you add small amounts to the chlorination mixture in addition to the catalyst Organic ones which boil higher than dichloropropionic acid and are soluble in the chlorination mixture Substances, e.g. B. aliphatic or aromatic sulfonic acid chlorides added.

Example 1 1630 parts of pure distilled o: -chloropropionic acid become 50 parts of sulfamic acid are added in a flask with a reflux condenser and added 175 "C heated. Chlorine is passed in with stirring until the density of the chlorination liquid is 1.440.

2050 parts of a yellow, clear crude acid are obtained and from it through Vacuum distillation at 120 "C 30 Torr 1750 parts 92.20% x ,, x-dichloropropionic acid.

Example 2 In a mixture of 1110 parts of propionic acid and 44 parts Amidosulfonic acid is refluxed in a flask with stirring at 120 "C for so long Chlorine gas introduced until the density of the liquid is 1.27. Then the Temperature increased to 175 "C and chlorine continued to be passed in until the liquid died Has a density of 1.455. A clear, red-brown crude acid without undissolved by-products is obtained and from it by distillation under reduced pressure 1600 parts of Qx, x-dichloropropionic acid with a salary of 900 / o.

Example 3 25 parts of monoethylamine are added to 1630 parts of x-chloropropionic acid and 50 parts of sulfuryl chloride are added and refluxed into this mixture at 165 "C. and stirring passed in chlorine until the density is 1.440. You get in this way a light, clear crude acid without undissolved components and from it through Distillation in vacuo 1720 parts of 91.00/0 strength s, r-dichloropropionic acid.

Example 4 A mixture of 4400 parts of pure, distilled, x-chloropropinonic acid with 132 parts of sulfamic acid and 132 parts of benzenesulfonyl chloride is at 175 "C. chlorinated in a stirred tank under reflux until the density is 1.452. A yellowish colored, clear crude product is obtained. By distillation under reduced Pressure gives 4700 parts of 91% x, x-dichloropropionic acid.

The distillation residue is thin, even after cooling.

Example 5 3000 parts of propionic acid are used in a stirred tank 150 parts of sulfamic acid and 180 parts len benzene sulfochloride added and under Stir and reflux at 120 "C up to a density of 1.27 chlorinated.

The temperature is then increased to 175 "C and further chlorine is introduced, until the liquid has reached a density of 1.450. The obtained in this way Raw acid is reddish yellow in color and completely clear. Obtained by vacuum distillation from it 4600 parts of 900 /, ige c4, a-dichloropropionic acid and a thin liquid Distillation residue.

Claims (5)

PATENT CLAIMS: 1. Process for the preparation of a, x-dichloropropionic acid by chlorination of propionic acid or α-chloropropionic acid in the presence of a catalyst and at elevated temperature, characterized in that the catalyst is a Compound of the general formula R '(R2) N-SO2X, in which R1 and g2 are hydrogen or identical or different, optionally substituted alkyl or aryl radicals and X represents a hydroxyl or alkoxy radical or a halogen atom is used. 2. The method according to claim 1, characterized in that one of the carboxylic acid to be chlorinated adds substances that are subject to the chlorination conditions form the catalytically active compounds. 3. The method according to claim 1 and 2, characterized in that one Amidosulfonic acid used as a catalyst. 4. The method according to claim 1 and 2, characterized in that one in addition to the catalyst higher than ss, a-dichloropropionic acid boiling and im Chlorination mixture soluble organic substances, such as aliphatic or aromatic Sulfonic acid chlorides, used. 5. The method according to claim 1 to 4, characterized in that one the chlorination, starting from propionic acid, at a temperature of 120 "C, starting of α-chloropropionic acid, at a temperature of 170 to 175 "C.