DE912334C - Process for the preparation of dehydrogucous acid dinitrile - Google Patents

Description

Process for the preparation of dehydroschleimsäuredinitril The in the Production of nitriles of monocarboxylic acids from the corresponding acid amides Processes which work with good yields, namely the heating of the acid amides with dehydrating agents such as P2 05, P2 S5, P C13, S O C12, acetic anhydride etc., often gives only low yields when applied to dicarboxylic acid diamides, because with bifunctional compounds by-products are very easily formed or Decomposition occurs. It has therefore been proposed to remove the water with acid chlorides, especially with phosgene, in the presence of a large amount of a tertiary amine or an acylated secondary amine, e.g. B. N-ethylformanilide to make. However this process is time consuming and requires a cumbersome work-up which losses to Ami @ d are inevitable.

The representation of dehydroschleimsäuredinitril comes across with normal Working method, e.g. B. when heating large amounts of diamide with P205 in a round bottom flask, to considerable difficulties, since the mass decomposes rapidly in the acidic medium and resinified, as is easily the case with furan compounds. The yields at Dinfril are so low that this process is technically insignificant.

It has now been found, surprisingly, that the (e.g. from Dehydroglucic acid: methyl ester and concentrated aqueous ammonia by heating The simplest form of dehydro-mucic acid diamide which can be easily represented at the reflux condenser Way and with very good yield in that dinitrile can be converted, if you have it with dehydrating agents in a thin layer for a short time to temperatures up to 300 °, preferably about aoo °, heated and the reaction product, advantageously immediately after the reaction has ended., distilled off in vacuo.

For example, the reaction mixture of diamide and dehydrating Means in a still pot with flat bottom and for purpose a short distillation path deeply set distillation head, for example a saber butt, spread out in a thin layer and carefully under normal pressure heated to about 200 °, the dinitrile being formed in a short time. It is not advisable to work at reduced pressure in this stage of the process, as this is the case the diamide would sublimate unchanged.

Immediately after the end of the reaction (about 5 to 10 minutes depending on Thickness of the layer) the dinitrile is now distilled off under reduced pressure, whereby it solidifies in the template when it cools to a light crystal mass, which through Recrystallization, e.g. B. from hot carbon tetrachloride, can be cleaned.

Instead of, as described, in a saber flask, the reaction can take place in larger scale in flat. level vessels or with continuous operation be made in thin film heaters.

Dehydroschleimsäuredinitril is a bifunctional compound for the production of synthetic resins.

Example 4o- Dehydroschleimsäurediamid, which was previously drained azeotropically with lylene, are: ground with twice the amount of P205 in a mortar and immediately poured into a 75o ccm saber flask with a flat bottom. One dips the flask into it. Oil: bath of 200 °, whereby the compound sinters together within 5 to 10 minutes and the dinitrile is formed. As soon as crystals settle on the upper neck of the flask, a water jet vacuum is applied, whereupon the dinitrile passes over as a colorless liquid at a pressure of 2 mm and 10 5 to 10 ° (bath temperature 200 °) and solidifies to form colorless crystals in the cooled receiver.

Towards the end of the distillation carried out at constant bath temperature the temperature is raised briefly to 250 °, the reaction mass foaming up. After the reaction has ended in this way, the dinitrile is treated with boiling carbon tetrachloride removed from the template and filtered hot.

The dehydro- mucic acid dinitrile separates in an analytically pure manner in colorless needles from a temperature of 66 °. Yield 26.5 g = 85%, based on the amount used Diamid.

Claims (3)

PATENT CLAIMS: i. Process for the production of: dehydro-mucic acid dinitrile, characterized in that dehydro-mucic acid diamide with dehydrating agents in a thin layer at temperatures up to 300 ° for a short time, preferably around --oo °, heated and the reaction product, expediently immediately after the end of the reaction, is distilled off in vacuo. 2. The method according to claim i, characterized in that that as a dehydrating agent P .., O "is used. 3. The method according to claim i and 2, characterized in that the reaction takes place in. Vessels with a flat bottom is carried out from a large surface.