DE1793203A1 - Process for the preparation of dialkylphosphine oxides - Google Patents

Description

FARBWERKE HOECHST AG. formerly Master Lucius & Brüning

Frankfurt (M) -Hoechst, August 15, 1968 Dr B / Eh

Appendix I.
for patent application Fw 5839

"Process for the production of dialkylphosphine oxides"

The hydrolysis of secondary monohalophosphines does not generally lead to the corresponding phosphine oxides, but rather with disproportionation to phosphinic acids and phosphines:

2 R ₂ PCl + 2H ₂ O ^ R ₂ tp; O) OH + R ₃ PH + 2HCl

(Kosolapoff "Organophosphorus Compounds" (195o), p. 52 and Van Wazer "Phosphorus and its Compounds" I (1964), pp. 354-5). The only exception are the diarylchlorophosphines, which hydrolyze to the corresponding diarylphosphine oxides permit. In the preparation of the compared to the multiply substituted Diphenylphosphinoxyds less stable Diphenylphosphinoxyds one must here the hydrolysis in organic Diluents in a hydrogen or nitrogen atmosphere Carry out acid-binding agents with pure water or in the presence of tertiary amines (Houben-Weyl "Methods of Organic Chemie ", XII, 1, p. 193-4).

* ÖAD ORIGINAL

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Of the dialkylphosphine oxides, only that could so far Dioctylphosphine oxide can be produced in this way, by hydrolysis of.Dioctylbromophosphine with molar Quantities of water and triethylamine in benzene under nitrogen.

The dioctylphosphine oxide is obtained in a yield of about 72% (J. Org. Chera. 24 (1959), p. 233).

It has also been reported that dimethylphosphine oxide in the hydrolysis of dimethylfluorophosphine or dinethylchlorophosphine to form with water (F. Seel et al. Angew. Chemie 79, p.

(1967)).

It has now been found that dialkylphosphine oxides of the general formula

where R and R ~ denote alkyl groups with 1 to 6 carbon atoms, Can be produced in excellent yield and in high purity if dialkylhalophosphines of the general formula

^R 1

*> PX
^R 2

in which R- and R ₂ are as defined above and X is a halogen atom, or their hydrogen halide adducts are treated with aqueous, non-oxidizing mineral acids.

Possible starting compounds are above all dialkylchlorophosphines and dialkylbromophosphines, monochlorophosphine being generally preferred because of its easier accessibility. Instead of the dialkylnonohalophosphines, their hydrogen halide adducts, which can also be present in the form of phosphoranes, can also be used. Examples of Dialkylnono- hh \ Offenpho> phine, which bo ι the orf indungsßenßen method as

2 0 9 8 1 £ / 1 7 4 2

OAS BATH

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Starting compounds that can be used are diraethylchlorophosphine, Dimethyl fluorophosphine, diethyl chlorophosphine, Diethylbromophosphine, methylethylchlorophosphine, dipropylchlorophosphine, Di-n-butylchlorophosphine and di-n-hexylchlorophosphine and their hydrogen halide, especially hydrogen chloride adducts.

The main non-oxidizing mineral acids are aqueous Hydrochloric acid, hydrobromic acid, sulfuric acid and phosphoric acid into consideration. The acid concentration to be used in the hydrolysis is mainly determined by the acid used in each case, the reaction temperature and the dialkyl halogen to be hydrolyzed. phosphine determined. Hydrochloric and hydrobromic acids are expediently in a concentration between about Io wt.% and the saturation concentration and preferably between about 3 o wt.% and the saturation concentration at the reaction temperature. Sulfuric and phosphoric acids are useful in a concentration between 2o and 8o% by weight, preferably between 3o and 5o% by weight, for use. In the production of higher dialkylphosphine oxides is generally a lower acid concentration than in the preparation of the lower members, especially of the dimethylphosphine oxide, sufficient. In general, concentrated hydrochloric acid is preferred as the hydrolysis mediura.

The hydrolysis is expedient at temperatures between -3ο and + 5o C, preferably between -2o and + 2o ° C. The hydrolysis is preferably carried out with the exclusion of air. Examples of suitable inert gases are argon, hydrogen chloride, Hydrogen bromide and especially nitrogen.

The aqueous mineral acid is used in at least such an amount used so that the reaction mixture obtained after addition of the dialkyl halophosphine is stirrable. The upper limit will be determined only by practical considerations.

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BATH ORIGINAL

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The hydrolysis is expediently carried out in the Yfeise that one the dialkylhalophosphines or their hydrogen halide addition products are allowed to flow into the aqueous mineral acid with stirring. As already mentioned, it is preferable to work with exclusion of air. After the reaction has ended, the conversion device is used on what can happen in different ways.

The work-up can be carried out, for example, in such a way that the water is largely distilled off under reduced pressure, the mineral acids neutralized and the inorganic acids formed Salts filtered off. The filtrate contains the crude alkylphosphine oxide. One can also proceed in such a way that the inorganic acids are neutralized before the water is distilled off undertakes. The neutralization is expediently carried out at temperatures below 50.degree.

For neutralization, alkali or alkaline earth oxides, hydroxides, carbonates or bicarbonates can be used. Sodium hydroxide, potassium hydroxide, barium hydroxide or calcium oxide are preferred used. Ammonia or organic amines, such as dimethylamine, diethylamine or triethylamine, can also be used. However, the amines should be selected so that the salts formed do not dissolve in the dialkylphosphine oxides. Also basic Ion exchangers can be used.

If volatile acids have been used as mineral acids, it is also possible to use them to add a large part of the acid remove by passing a stream of inert gas, such as nitrogen, through the mixture to be worked up.

In the work-up methods given above, it is often advantageous in the presence of an inert diluent, such as Benzene, methylene chloride or a lower alcohol, to work:;, which is distilled off again after the inorganic salts have been filtered off.

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ORIGINAL

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The products of the process can also be carried out by extraction, which is carried out before or after the neutralization of the solution mixture can be won. Diethyl ether, benzene or methylene chloride are particularly suitable as extraction agents. After separating the organic layer, the extractant, optionally after neutralization and drying, distilled off. The recovery of the process products by extraction is recommended in general only in the higher members, from the dipropylphosphine oxide upwards, since the lower members, especially the dimethylphosphine oxide, are very soluble in water.

The crude dialkylphosphine oxides thus obtained can then by Distillation under reduced pressure or by recrystallization getting cleaned.

The advantage of the method according to the invention over the previously known processes for the preparation of dialkylphosphine oxides is that technically easily accessible starting compounds are used, the dialkylphosphine oxides in so far yields not yet achieved are obtained and that according to the process of the present invention also Dinethylphosphinoxyd, which could not be obtained in substance according to the previously known methods, can be produced, and even almost quantitative yield.

It was very surprising that the hydrolysis according to the fiction According to the straight process, there is no or practically no disproportionation to phosphinic acids and phosphines. This is all the more surprising than the tendency to disproportionate with decreasing number of carbon atoms in the organic residues increases (Am. Soc. 77, (1955), p. 3412 and Houben-w'eyl "methods der Organischen Chemie ", XII, 1, p. 193). For example, dimethylchlorophosphine is left in excess water under nitrogen flow in at 0 ° to lo ° C, and then neutralize with sodium hydroxide solution while maintaining a temperature of about O C, so one observes a spontaneous one towards the end of the neutralization

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,,, BAD ORIGINAL

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Inflammation, leading to the release and self-ignition of the Dimethylphosphine formed by disproportionation is due. Furthermore, red-yellow polymeric phosphorus compounds are used here deposited. Only the sodium salt of dimethylphosphinic acid could be isolated during work-up.

In view of the fact that secondary phosphine oxides have a strong tendency when heated in an intermolecular redox reaction To disproportionate to secondary phosphines and phosphinic acids (Houben-Weyl, loc. cit. p. 64) it was further here It is surprising that the lower dialkylphosphine oxides, especially dimethylphosphine oxide, are also distilled without decomposition can be.

The dialkylphosphine oxides obtainable by the process of the present invention are valuable intermediates. Due to their high purity, they are particularly suitable as reaction components for reactions caused by radical formers be catalyzed.

The lowest member in the series of dialkylphosphine oxides, dimethylphosphine oxide, also has bacteriostatic and bactericidal properties.

It can also be used as an oil- and water-soluble corrosion inhibitor and in this context is of Interest as a lubricating oil additive.

Polyesters, epoxy resins or polyurethanes can be added can be made flame retardant by dimethylphosphine oxide. The dimethylphosphine oxide can be used during the production of the Polymers are added; however, the polymers can also be treated with dimethylphosphine oxide after they have been prepared.

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Example 1:

185 g of Diwethylchlorphosphin are evenly concentrated in 165 g Hydrochloric acid at -5 ° C under a nitrogen atmosphere allowed to flow in within about 1 1/2 hours. After the reaction has ended, the reaction mixture becomes with concentrated sodium hydroxide solution brought to a pH value of 6.5, the temperature should not exceed 2o to 3o ° C. Most of the water is then distilled off under reduced pressure at a maximum internal temperature of about 6oC. ^ Then 300 ml of benzene are added and the remainder of the ™ Water removed by azeotropic distillation. After that, the Sodium chloride sucked off and rinsed with 3ο nil benzene. The benzene is then distilled off at a maximum internal temperature of about 60 to 70 ° C. under reduced pressure. 146 g of crude Dinethylphosphinoxyd are obtained, which is a yield of 97.5% corresponds to theory. The purification is carried out by distillation with the aid of a column, with a cooling water temperature of 40 ° C is maintained. The pure diraethylphosphine oxide thus obtained has a boiling point / l Torr of 54 ° C, a freezing point of 34 to 36 C and has a refractive index η ^ - 1. 445o.

Example 2:

255 g of dimethylchlorophosphine-hydrogen chloride adduct are obtained under a hydrogen chloride atmosphere in 165 g of concentrated hydrochloric acid at a temperature of -lo ° C within 1 1/2 hours dripped in evenly. After completion of the reaction, the water is distilled off under reduced pressure, whereupon the residue is taken up in 3oo ml of methylene chloride. Gaseous ammonia is introduced into this solution with cooling until it is neutralized, whereupon remaining traces of water through azeotropic

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Distillation can be removed. It is then filtered off with suction and rinsed with 3o ml of methylene chloride. After the methylene chloride has been distilled off, 146 g of crude dimethylphosphine oxide are obtained, which corresponds to a yield of 97.5 % of theory.

Purification of the product similar to that described in Example 1 Product is identical, takes place in that described in Example 1

Way.

Example 3:

Io8 g of diethylchlorophosphine are added under a nitrogen atmosphere in 80 g of concentrated hydrochloric acid at - Io C within 80 minutes dripped in evenly. Then at a temperature not exceeding 3o to 4o ° C with 5o% sodium hydroxide solution up to neutralized to a pH of 7. The water is then distilled off under reduced pressure, whereupon 200 ml of benzene are added and the last traces of water are distilled off azeotropically. After the suction, the benzene is distilled off under reduced pressure. The crude diethylchlorophosphine obtained as residue is then distilled in a high vacuum.

This gives 86 g Diäthylphosphinoxyd, Kp _"m: 47 - 48 ° C

O f Δ IuIu

(Yield 93.5% of theory). Example 4:

100 g of diethylbromophosphine are allowed to flow uniformly into 100 g of 48% hydrobromic acid at -lo ° C. over the course of 1 hour under a nitrogen atmosphere. After the reaction has ended, the reaction mixture is worked up in the manner described in Example 3. 57 g of diethylphosphine oxide are obtained in this way, corresponding to a yield of 90 % of theory.

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Example 5:

121 g of dimethylchlorophosphine are uniformly dripped into 5oo ml of 50% strength sulfuric acid at -2o ° C. under a nitrogen atmosphere over the course of about 1 hour. After the reaction has ended, the reaction mixture is brought to a pH of 7 by adding 50% strength sodium hydroxide solution. A temperature of 20 to 30 ° C is maintained here. The sodium sulfate which has separated out is then filtered off with suction and washed with a little methanol. Methanol and water are then distilled off under reduced pressure. Methanol is added to the residue, and the remaining sodium sulfate is filtered off with suction and washed with a little methanol. After the methanol has been distilled off under reduced pressure, 89 g of diraethylphosphinoxyc are obtained as residue, which corresponds to a yield of 90 % of theory. The crude product is purified in the manner described in Example 1.

Example 6:

181 g of di-n-butylchlorophosphine are allowed to flow into 2oo ml of 20% hydrochloric acid at + 10 ° C. under a nitrogen atmosphere over the course of about 1 hour. After the reaction has ended, the mixture is brought to a pH of 7 by adding 50% strength sodium hydroxide solution. The oil that separates out is extracted with ether. After the ether has been distilled off, the di-n-butylphosphine oxide thus obtained is purified by distillation under reduced pressure. 149 g of di-butylphosphine oxide are obtained, which corresponds to a yield of 92 % of theory; Bp _lg : 153 ° C.

Is used in the above example instead of di-n-butylchlorophosphine the equivalent amount of di-n-butylbromophosphine and proceeds in

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2 0 9 B 1 5 / m 2

BATH ORIGINAL

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rest as described above, so nan receives the same Compound in approximately the same yield.

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0 Ur- ■ *

Claims (4)

- 11 - Pw 5839 patent claims: 1. Dimethylphosphine oxide of the formula ^CH 3 \ » P-H 2. Process for the preparation of dialkylphosphine oxides of the general formula P-H ^R 2 wherein R .. and R _{2 are} alkyl groups having 1 to 6 carbon atoms, characterized in that dialkyl halophosphines of the general formula ^Rl > -x • where R- and R _? have the abovementioned meaning and X is a halogen atom, or their hydrogen halide adducts are treated with aqueous, non-oxidizing mineral acids. 3. The method according to claim 2, characterized in that one the reaction is carried out with exclusion of air. 4. Process according to Claims 2 and 3, characterized in that the non-oxidizing mineral acid used is hydrochloric acid, Hydrobromic acid, sulfuric acid or phosphoric acid used. 2098 15/1742 BATH ORIGINAL