DE1130425B - Process for the production of monomeric chloro-acetaldehyde - Google Patents

Description

It is known that polymeric formaldehyde or acetaldehyde can easily be converted into the monomeric form can, if the polymeric aldehyde in the presence of small amounts of sulfuric acid or Toluenesulfonic acid and heated the resulting monomeric aldehyde at the same time by distillation removed from balance. Chloroacetaldehyde easily forms the polymeric form and can therefore be also very difficult to depolymerize. To do this, one must use temperatures at which decomposition is easy of the aldehyde occurs. When using sulfuric acid or toluenesulfonic acid, the yield is on monomers! Chloro-acetaldehyde low and the loss of valuable starting material through resinification of the residue large.

It has been found that monomeric chloroacetaldehyde can be obtained in a simple manner in good yield can produce acid by heating the polymeric chloroacetaldehyde in the presence of small amounts, if the acids used are oxalic acid and / or haloacetic acids. The depolymerization will carried out in a manner known per se in such a way that the polymeric chloro-acetaldehyde is added the organic acid is heated to temperatures of 100 to 300.degree. C., preferably 130 to 200.degree and the resulting monomeric aldehyde is distilled off at the same time. Of the haloacetic acids Trichloroacetic acid is particularly suitable. The acids mentioned can be used either alone or as a mixture can be used. The amount used is 0.1 to 20, preferably 1 to 10 percent by weight, based on the polymeric chloro-acetaldehyde. Higher acid concentrations can be used but do not bring any benefit. The reaction proceeds at concentrations below 0.1% too slow.

The process allows the production of a pure chloroacetaldehyde in a yield of at least 9O '%>. Monomeric chloro-acetaldehyde is a valuable one Intermediate product for the synthesis of pharmaceuticals and plant protection products.

A multistage process for the depolymerization of chloroacetaldehyde is also known, the monomeric aldehyde first being converted into the trimeric form by treatment with sulfuric acid and then converted back into the monomeric form by distillation. In this multistage procedure, the monomeric form is only obtained in moderate yield. Since chloro-acetaldehyde is extremely sensitive to thermal influences, heat treatment of the trimer alone without the addition of a catalyst leads to the most extensive manufacturing processes
of monomers! Chloro-acetaldehyde

Applicant:

Chemical works Hüls Aktiengesellschaft,
Marl (district of Recklinghausen)

Dr. Rudolf Brockhaus and Dr. Walter Stumpf,

Marl (district of Recklinghausen),
have been named as inventors

Decomposition. The trimeric chloro-acetaldehyde obtained in the known technical processes, the undergoes no acid pretreatment, cannot be depolymerized by heat treatment alone. The known use of mineral acids or p-toluenesulfonic acid in depolymerization of acetaldehyde does not suggest that the claimed carboxylic acids contribute to good yields lead to the depolymerization of chloro-acetaldehyde, all the more so than the use of the known Acids cause extensive resinification and decomposition of the chloroacetaldehyde.

With the selected acids, however, it is possible to obtain pure monomeric chloroacetaldehyde in one yield of over 90%.

The table below shows the results of the comparative tests with those previously known Acids combined.

209 607/355

acid acid
lot
° / o Reaction
temperature
⁰ C yield
% Distillation residue 1
2
3
4th
5
6th H ₀ SO, 2
4th
10
5
10
3 145
145
145
145
145
145 40
50
90
92
90
88 resinified
resinified
practically no residue
practically no residue
practically no residue
practically no residue Toluenesulfonic acid
Oxalic acid
Oxalic acid
Trichloroacetic acid
Trichloroacetic acid

example 1

10 g of trimeric chloroacetaldehyde are combined with 1 g of oxalic acid in a cooler with descending order Flask heated to 145 ° C in an oil bath. The resulting monomeric chloro-acetaldehyde is continuously distilled off. When the main amount has distilled over, the temperature in the reaction flask is increased up to 200 ° C. 9 g of monomeric chloroacetaldehyde are obtained, that is 90% of the calculated value Lot.

Example 2

According to Example 1, 10 g of trimeric chloroacetaldehyde with 0.5 g of oxalic acid in one with The flask fitted with a descending condenser was heated to 145 ° C in an oil bath. 9.2 g (= 92% theory) monomeric chloroacetaldehyde.

Example 3

heated to 145 ° C in an oil bath. 9 g (= 90% of theory) of monomeric chloroacetaldehyde are obtained.

Example 4

10 g of trimeric chloroacetaldehyde are in accordance with Example 1 with 0.3 g of trichloroacetic acid in heated in a flask equipped with a descending condenser in an oil bath to 145 ° C. 8.8 g are obtained (= 88% of theory) monomeric chloroacetaldehyde.

Claims (1)

PATENT CLAIM: Process for the preparation of monomeric chloroacetaldehyde by heating polymeric chloroacetaldehyde in the presence of small amounts of acid, characterized in that the acids used are oxalic acid and / or haloacetic acids. As described in Example 1, 10 g of tri- Considered publications: merer chloro-acetaldehyde with 1 g of trichloroacetic acid Ullmann's Encyclopedia of Industrial Chemistry, in a piston provided with a descending cooler 35 5, 1954, p. 319. © 209 607/355 5.62