DE2344332C3 - Process for the preparation of vinylphosphinic acids - Google Patents

Description

CH, =

wherein R is an alkyl group with 1 to 18 carbon atoms or an aralkyl or aryl group with 6 to 10 is C atoms means, characterized that 2-hydroxyethylphosphinic acids of the general formula (II)

R O

\ ll

P-OH

/
HIGH ₂ -CH ₂

OD

in which R has the abovementioned meaning, ^{heated to temperatures of 120 to 30O 0} C and the water split off is removed in a manner known per se

Vinylphosphinic acids are already known. For example, vinylphenylphosphinic acid has already been produced by hydrolysis of vinylphenylphosphinic acid ethyl ester or chloride [P. Mastalerz, Roczniki Chem, 34, 1161 (1960); EL Gefter et al, 2nd obäc. Chim., 31,955 (1961) \ The vinylphenylphosphinic acid derivatives required for this purpose are obtained from the corresponding 2-chloroethyIphenylphosphinic acid derivatives by splitting off hydrogen chloride with the aid of bases, such as. B. tertiary amines, accessible.

It has now surprisingly been found that vinylphosphinic acids of the general formula (I)

R O

CH ₂ = CH

P-OH

(D

wherein R is an alkyl group with 1 to 18 carbon atoms, preferably 1 to 4 carbon atoms, or an aralkyl or Aryl group with 6 to 10 carbon atoms can be obtained by adding 2-hydroxyethylphosphinic acids of the general formula (II)

R O

HIGH ₂ -CH ₂

P-OH

(Π)

Temperatures of 120 to 300 ° C and heated the split off water in a known manner removed

It can be useful in some cases, with the exclusion of atmospheric oxygen or, under one Inert gas atmosphere, such as. B, nitrogen or argon, too work.

As starting compounds of the formula (II), for. B. in question:

2-hydroxyethylmethylphosphinic acid,

2-hydroxyethylethylphosphinic acid,

2-hydroxyethylbutylphosphinic acid,

2-hydroxyethyloctylphosphinic acid,

2-hydroxyethyloctadecylphosphinic acid,

2-hydroxyethylphenylphosphinic acid,

2-hydroxyethylbenzylphosphinic acid,

2-hydroxyethyl - /? - naphthylphosphinic acid.

in which R has the abovementioned meaning, on The said 2-hydroxyethylphosphinic acids Easily accessible by hydrolysis of the corresponding 2-AcetoxyäthyIphosphinsäureester, which after the process of DE-OS 21 27 821 can easily be prepared from vinyl acetate and phosphonous esters, or by Hydrolysis of 2-Hydroxyäthylphosphinsäureestern, the can be obtained by the method of patent application P 23 35 8523. These procedures are technically easy to carry out and provide the desired products in high purity in good yield It is advisable to start from such pure products, especially when the after Process of the present invention produced vinylphosphinic acids used for polymerizations should be.

The process is carried out in such a way that the 2-hydroxyethylphosphinic acid under vacuum, expediently under a vacuum of about 25 Torr to about 0.1 Torr, to temperatures of about 120 ^° C. to about 300 ^° C., preferably 140 to 250 ^° C, is heated. The cleavage reaction then leads to the corresponding vinylphosphinic acid, while the ge. formed water can be condensed in a cold trap downstream of the reaction vessel. The resulting vinylphosphinic acid can at least partially distill off from the reaction vessel during the cleavage process, but it can also remain in the reactor, especially if the molecular weight is high, ie high R or higher pressure. In this case, a subsequent cleaning, e.g. B.

so by recrystallization. Of course, you can also use the water at higher pressures up to z. B. Remove atmospheric pressure by passing a stream of inert gas, e.g. B. nitrogen or argon, passes through
The process can also be carried out continuously. The use of a thin-film evaporator can be particularly advantageous here.

Polymerization inhibitors familiar to the person skilled in the art, such as hydroquinone and thiosemicarbazide, can be used to a lesser extent Amount to be added in order to avoid polymerization during the course of the reaction.

The vinylphosphinic acids which can be prepared by the process of the present invention are valuable Intermediate products for the production of flame retardants and corrosion inhibitors. Furthermore they are valued intermediate products, for example in the manufacture of pesticides.

The invention is illustrated by the following examples.

example 1

A solution of 150 g of isobutyl 2-hydroxyethyl methyIphosphinate in 250 ml of 20% hydrochloric acid is heated to 100 ° C. for 9 hours to split off the ester group and then concentrated in a rotary evaporator under a water jet vacuum 155 ° C distilled After further fractionation 81 g Vinylmethylphosphinsäure, Kp ^ _0, one obtains:.. 128 ° - 130 ° C, corresponding to a yield of 92%

the theory. _. . , "

Example 2

200 g of isobutyl 2-hydroxyethylphenylphosphinate apply in approx. 450 ml of concentrated hydrochloric acid

100 ° C held while at the same time hydrogen chloride is initiated. After 10 hours, use a rotary evaporator distilled off under a water jet vacuum, finally at 0.5 torr and an internal temperature of 100.degree. The residue represents crude 2-hydroxyethylphenylphosphinic acid, mp 50 ° -55 ° C.

120g of 2-hydroxyethylphenylphosphine acid are held at 240 ° C and 3 torr for 1.5 hours. In a cold trap downstream of the reaction apparatus the separated water condenses. Then the reaction mixture is cooled and with about the double Amount of water stirred. The vinylphenylphosphinic acid precipitates and is filtered off with suction Λ7 g obtained (melting point: 107 ° -109 ° C. after recrystallization from benzene). This corresponds to a yield of 62% of theory.

Claims (1)

Claim: Process for the preparation of vinylphosphinic acids of the general formula (I) R O ll P-OH (D IO