DD147901A4 - PROCESS FOR PREPARING ALLANTOIN - Google Patents

Abstract

The invention relates to a process for the preparation of allantoin according to DD145016 with d. The aim, d. To reduce formation of polymeric condensation products of urea and chloral hydrate and to increase the degree of purity of the allantoic formed. Chloral hydrate is thereby added with the addition of lower aliphatic alcohols, preferably methanol, or hemiacetals of the chloral with these alcohols, e.g. Chorale-methylhalbacetale in aqueous solution with a hydroxylammonium salt and urea at 10 to 50 degrees C reacted. 0.5 to 2 moles of hydroxylammonium salt and 1 to 2 moles of a lower aliphatic alcohol are preferably used per mole of chloral hydrate. Furthermore, adducts of the chloral to ammonia, amines, semicarbacides or urea can be used instead of chloral hemiacetals. Furthermore, it is advantageous to add the urea from the outset to the reaction mixture. Allantoin is used as a cell-regenerating agent in medicine and cosmetics.

Description

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Title of the invention

Process for the preparation of allantoin

Field of application of the invention

The invention relates to a process for the preparation of allantoin according to DD 14-5 o16 and relates to the improvement of the economy during the reaction and the increase in the degree of purity of the formed allantoic ·

Allantoin is used as a cell-regenerating agent in cosmetics and medicine ·

Characteristic of the known technical solutions

Subject of the DD 14-5 o16 ι ± _Q t a process for the preparation of allantoin, wherein chloral hydrate is reacted in aqueous solution with hydroxylammonium salt and then with urea at 40 to 10O ⁰ C *

Object of the invention

It is an object of the invention to reduce the process for producing allantoin by reducing the formation of polymeric condensation products of urea and chloral hydrate and thus to increase the degree of purity of the allantoic formed.

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Explanation of the essence of the invention

This object is achieved by chloral hydrate according to the invention with the addition of lower aliphatic alcohols or hemiacetals of the chloro be reacted with these alcohols in aqueous solution with a hydroxylammonium salt and urea at 10 to 50 ⁰ C.

The degree of purity of the allantoic formed increases when 0.5 to 2 mol, preferably 1 to 1.5 MoI _{1 of} a hydroxylammonium salt are reacted at 20 to 30 ⁰ C per mole of chloral hydrate and the subsequent reaction with 2 to 5 moles of urea at 20 up to 50 ° C ·

It is also possible to add 1 to 2 moles of a lower aliphatic alcohol, for example methanol, per mole of chloral hydrate in order to likewise improve the purity of allantoin.

It is also possible to use, instead of the chloral hydrate, bromine hydrate or its hemiacetals with lower aliphatic alcohols, such as chloro-methyl-hemiacetal. Furthermore, good results have been achieved by using, instead of chloral hemiacetals, adducts of the chloral to ammonia, amines, semicarbazides or urea.

It has proved to be very economical to add urea to the reaction mixture in advance, which simplifies allantoin synthesis to a single-stage process.

Example 1:

A solution of 180 g of technical Chloralmethylhalbacetal in 180 ml of water at 20 to 30 ° C with 512 g of technical 16% hydroxylammonium sulfate solution (HAS) (corresponding to 82 g (NHpOH) 'H added (by the acidity of the technical used HAS solution consumes 1 ml of the reaction mixture 12 ml 0, in NaOH). If the acid content of the reaction solution corresponds to a 0.1 N NaOH consumption of 35 to 50 ml / ml, 300 g of urea are added and allowed to crystallize completely The extracted, washed with hot methanol crude product is from

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Recrystallized water or reprecipitated from dilute NaOH »Yield: 63 g = 40 % of theory; F .: 232 to 235 ° C.

Example 2:

The procedure is as described in Example 1, but instead of Chloralmethylhalbacetals 164.5 g of chloral hydrate and 32 g of methanol.

Example 3:

The procedure is as described in Example 1, but one sets the urea the reaction mixture from the outset to »

Claims (5)

invention claim 1 · Process for the preparation of allantoin by reaction of chloral hydrate in aqueous solution with hydroxylammonium salt and subsequent addition of urea at 40 to 100 ⁰ C to DD 145 o16 _# characterized in that chloral hydrate with the addition of lower aliphatic alcohols or Halbacetale of the chloral with these alcohols be reacted in aqueous solution with a hydroxylammonium salt and urea at 10 to 50 ⁰ C · Method according to item 1, characterized in that 0.5 to 2 mol, preferably 1 to 1.5 mol, of hydroxylammonium are used in the form of a salt per mol of chloral hydrate. 3 * Process according to item 1, characterized in that 1 to 2 moles of a lower aliphatic alcohol are added per mole of chloral hydrate. 4. Method according to point 1, characterized in that chloralmethyl hemiacetal is used as the hemiacetal. 5 · Process according to items 1 to 4, characterized in that urea is added at the beginning of the reaction.