CH622524A5 - Process for the preparation of alkanephosphonic esters - Google Patents

Description

The invention is illustrated by the following examples.

example 1

200 g (2.47 mol) of phosphorous acid and 268 g (2.47 mol) of dimethyl phosphite are mixed and heated to 170 ° -175 ° C. under a nitrogen atmosphere. A mixture of 545 g (4.87 mol) of octene-1 and 6 g of di-tert-butyl peroxide is then added dropwise with vigorous stirring over a period of 2.25 hours. The mixture is stirred at this temperature for 1 hour. In a downstream cold trap, 12 g of dimethyl ether, 5.5 g of methanol and 1.5 g of octene-1 collect. There remain 1000 g of octane-phosphonic acid derivatives which, based on a gas chromatographic analysis, consist of 13% by weight of dimethyl octanephosphonate, 55% by weight of mono-methyl ester and 29% by weight of octanephosphonic acid and only 0.5% by weight. Telomeri-sat included.

The yield is thus almost 100% of theory of octanephosphonic acid derivatives.

Example 2

250 g (3.05 mol) of phosphorous acid, 450 g of n-butanol and

345 g of toluene are heated to reflux with stirring, 65 ml (3.62 mol) of water being separated off in about 4 hours with the aid of a water separator. Then distilled at 100-120 torr to an internal temperature of 150 ° C. The residue is crude mono-n-butyl phosphite. It is heated to 180 ° C. under a nitrogen atmosphere. A mixture of 342 g (3.05 mol) of octene-1 and 3.5 g of di-tert-butyl peroxide is then added dropwise with vigorous stirring over a period of 3 hours. The mixture is stirred at this temperature for 1 hour. About 5 g of butene-1 collect in a cold trap.

The reaction product is then reacted with water at 200 ° C. using the process of German patent application P 24 41 783.2. 592 g of octanephosphonic acid are obtained, which contains only 2% by weight of telomerizate. This corresponds to a yield of 100% of alkanephosphonic acid derivatives.

Example 3

120 g (0.618 mol) of di-n-butyl phosphite and 50.6 g (0.618 mol) of phosphorous acid are mixed and heated to 180 ° C. under a nitrogen atmosphere. A mixture of 139 g (1.24 mol) of octene-1 and 1.4 g of di-tert-butyl peroxide is then added dropwise with vigorous stirring over a period of 2.5 hours, and the mixture is subsequently stirred at this temperature for 1 hour. Then distilled to an internal temperature of 150 ° C at 1 Torr. 295 g of a mixture of octanephosphonic acid dibutyl ester, octanephosphonic acid monobutyl ester and octanephosphonic acid remain in the residue, approximately in the ratio as described in Example 1.

Example 4

162 g (1.975 mol) of phosphorous acid and 217 g (1.975 mol) of dimethyl phosphite are mixed and heated to 155 ° C-160 ° C. A mixture of 775 g (3.95 mol) of tetradecene-1 and 8 g of di-tert-butyl peroxide is then added dropwise under a nitrogen atmosphere with vigorous stirring and the mixture is stirred at this temperature for 1 hour. 19 g of dimethyl ether and methanol collect in a downstream cold trap. When the reaction mixture cools down, solidification occurs. The product obtained has a solidification point of 35 ° C.

The reaction product is then reacted with water at 175 ° C. using the process of German patent application P 24 41 878.8. 1080 g of tetradecane-phosphonic acid with a solidification point of 74 ° C. are obtained. This corresponds to a yield of 98.5% of theory of tetradecane-phosphonic acid.

Example 5

200 g (2.44 mol) of phosphorous acid and 268 g (2.44 mol) of dimethyl phosphite are mixed and heated to 155-160 ° C. A mixture of 545 g (4.87 mol) of octene-1 and 6 g of di-tert-butyl peroxide is then added dropwise under nitrogen atmosphere with vigorous stirring for 2 hours.

The mixture is stirred at this temperature for 1 hour. 8 g of dimethyl ether and 1.5 g of methanol collect in a downstream cold trap.

The reaction product is then reacted with water at 170 ° C. using the process of German patent application P 24 41 878.8. 941 g of octanephosphonic acid with a solidification point of 80.6 ° C. are obtained. This corresponds to a yield of 99% of theory of octane phosphonic acid.

s io

15

20th

25th

30th

35

40

45

50

55

60

65

B

Claims (5)

622 524 2. The method according to claim 1, characterized in that the reaction is carried out in the presence of UV light. 2nd PATENT CLAIMS 1. Process for the preparation of alkanephosphonic acid monoalkyl esters of formula I. OR2 «\ O OH in which R1 is an alkyl group with 4 to 22 C atoms and R2 is an alkyl group with 1 to 22 C atoms, characterized in that monoalkyl phosphites of the formula II OR2 HP "\ O OH in which R2 has the meaning given above, with sulfur-free or virtually sulfur-free a-olefins which contain 4 to 22 carbon atoms, in the presence of free-radical formers at temperatures of 150 to 200 ° C. 3rd 622524 by mixing equimolar amounts of phosphorous acid with the corresponding dialkyl phosphite. Because of the above-mentioned equilibrium in the starting product of the formula II, a mixture of alkanephosphonic acid derivatives consisting of alkanephosphonic acid mono- and dialkyl esters and alkanephosphonic acid, which can be obtained in a manner known per se, e.g. B. by distillation or chromatographically separated and the main component of which is the desired alkanephosphonic acid monoalkyl ester. Such a mixture can also be worked up, in particular, by first neutralizing the reaction mixture with alkalis while cooling. The constituents of the neutralized mixture are essentially the alkali metal salts of the alkanephosphonic acids and the alkanephosphonic acid monoesters, furthermore the alkanephosphonic acid diesters. The alkanephosphonic diesters can in principle be separated from this by extraction with an organic solvent. The alkali metal salts of the alkanephosphonic acids and the alkanephosphonic acid monoesters can then be isolated on account of their different solubilities in alcohols, preferably in methanol. According to the invention, it is not necessary to start from pure “monoalkyl phosphites”, that is to say from products of the formula II in which exactly one ester group per molecule comes on average. Rather, mixtures can also be used as monoalkyl phosphites in which more phosphoric acid or more dialkyl phosphite can be contained than corresponds to a “monophosphite”. However, since the phosphorous acid is more difficult to convert under the reaction conditions, it is advantageous to start from mixtures which contain 0.9 to 1.5, in particular 1.1 to 1.3, ester groups to one molecule. Examples of suitable monoalkyl phosphites for the process according to the invention are into consideration: monomethyl phosphite, mono-ethyl phosphite, mono-n-propyl phosphite, monoisobutyl phosphite, mono-n-butyl phosphite, mono-n-hexyl phosphite, mono-n-dodecyl phosphite, mono-n-eicosyl phosphite. Lower (Ci-C4) alkyl phosphites are preferred. The a-olefins used in the present process contain 4 to 22 carbon atoms, preferably 4 to 12 carbon atoms. In the present process, not only straight-chain a-monoolefins can be used, but also isomeric a-monoolefins with a branched chain. Examples of such olefins are butene (1), hexene (1), octene (1), dodecene (1), tetradecene (1), hexadecene (1), octadecene (1), heneicose ( l), Docosen- (l), 2-methyl-pentene (l) and 2-ethylhexene (l). Mixtures of such olefins can also be used. They are generally preferably used in a stoichiometric amount or in a slight excess, up to 10% by weight, based on the stoichiometric amount required. For the process according to the invention to be successful, it is crucial that the a-monoolefin used is sulfur-free or almost sulfur-free, which means a bound sulfur content of less than 0.002%. It has been shown that even a content of about 0.02% of bound sulfur leads to considerable reductions in yield. In the process according to the invention, use is advantageously made of those α-olefins which are sulfur-free from the outset due to their production process. Such a process is, for example, the so-called Ziegler or Mühlheimer process, in which ethylene is dimerized or oligomerized in the presence of catalysts, especially aluminum triethyl, to give straight-chain a-olefins. Branched α-olefins, such as, for example, 2-methylpentene (1) and 2-ethylhexene (1), can also be prepared by the same procedure. for example by dimerizing propene or isobutylene (cf. F. Asinger “Chemistry and Technology of Monoolefins” [1957], especially pages 178-180). The dimerization can also be carried out in other ways, e.g. by catalysis with the help of alkali metals. It is of course also possible to use α-olefins as starting compounds which have been obtained by other known processes, for example by cracking petroleum distillates or waxes, by hydrogen chloride elimination from terminally chlorinated paraffins or by dehydration of terminal alcohols. It is only essential that these olefins are sulfur-free or practically sulfur-free. Otherwise, the sulfur must be removed completely or almost completely by suitable measures, for example by catalytic desulfurization. All known radical formers can be used as radical formers in the present process. Examples include di-tert-butyl peroxide, tert-butyl peroxybenzoate, 2,5-dimethyl-bis-2,5- (peroxybenzoate), tert-butyl hydroperoxide, dicumyl peroxide and benzoyl peroxide. The radical formers are used by dissolving them in the reaction component (s) which are (are) introduced into the reaction space. It may prove necessary to additionally use an inert solvent as solubilizer. However, the radical generator may not be soluble in the olefin, but it may be soluble in the monoalkyl phosphite. In this case, part of the total monoalkyl phosphite in which the radical generator is dissolved can be used separately next to the olefin. Furthermore, the monoalkyl phosphite can also be used as a solubilizer for the radical generator in the olefin. The radical formers are used in catalytic amounts. It is expedient to use 0.1 to 5 mol%, preferably 0.5 to 3 mol%, based on the amount of olefin used. Di-tert-butyl peroxide is preferably used. If UV light radiation is used to excite the reaction, the reaction solution must be exposed to direct radiation from a UV lamp. The reaction according to the invention is expediently carried out in such a way that the olefin, optionally mixed with catalytic amounts of a radical generator, is slowly added to the monoalkyl phosphite. Low-boiling olefins are advantageously added in such a way that the outflow pipe of a dropping funnel leads below the surface of the monoalkyl phosphite. Monoalkyl phosphite and olefin are preferably used in a molar ratio of about 1: 1. It is of course also possible to use one of the reactants in excess. However, this does not generally result in an advantage when using radical formers. The reaction can also be carried out in the presence of inert solvents. Examples include alcohols, esters and hydrocarbons, such as. B. Benzene. However, it is preferred to work in the absence of solvents. The reaction is preferably carried out under an inert gas atmosphere. Argon and nitrogen are particularly suitable as inert gases. As a result of the possible decomposition reactions described above, corresponding decomposition products, e.g. Ethers, alcohols, olefins, for example dimethyl ether, methanol, butene-1 are formed in small amounts during the reaction. Such decomposition products can, for example, advantageously be carried out from the reaction space with the aid of the inert gas when the reaction is carried out under an inert gas atmosphere and e.g. in a subsequent cold trap 5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 622524 3. Process according to claims 1 and 2, characterized in that the reaction is carried out at temperatures of 160 to 180 ° C. 4. Process according to claims 1 to 3, characterized in that monoalkyl phosphites are used which contain 0.9 to 1.5, in particular 1.1 to 1.3, ester groups to one molecule. 5. Process according to claims 1 to 4, characterized in that the a-olefins are used in a stoichiometric amount or in a slight excess, up to 10% by weight, based on the stoichiometric amount. 6. The method according to claims 1 to 5, characterized in that one carries out the reaction under an inert gas atmosphere. 7. Process according to claims 1 to 6, characterized in that di-tert-butyl peroxide is used as the catalyst. 8. Use of the alkanephosphonic acid monoalkyl ester of the formula I, prepared according to claim 1, characterized in that the reaction mixture obtained is converted hydrolytically into alkanephosphonic acid. will. An extension of this process to monoalkyl phosphites or even the phosphorous acid did not appear possible in view of the high temperatures required, after it was expected that, unlike dialkyl phosphites, monoalkyl phosphites and phosphorous acid would disproportionate or decompose at temperatures above 150 ° C (see. (I), e.g. DE-OS 2,121,832, U.S. Patent 2,834,797, L. Hackspill et al., Chim. Ind. 27 [1932], 453-473), e.g. with formation of alkyl ethers and mixtures of hydrocarbons, as is also known from acidic esters of phosphoric acid (cf. D.E. Pearson, J. Chem. Soc., Chem. Commun. 1974, 397). In particular, however, it was to be expected that the peroxides used as radical formers in the acidic reaction medium ls and in the presence of the phosphorous acid known as reducing would be rapidly destroyed at temperatures above 150 ° C. (II), which and thus their initiating effectiveness would not be able to develop (cf. Houben-Weyl, Methods of Org. Chemistry, Vol. VIII [1952], pp. 66-67, 73-74). 20 It was therefore all the more surprising compared to this prior art that monoalkylphosphites can be reacted with olefins to give alkanephosphonic acid monoalkyl esters even and especially at temperatures above 150 ° C. and with far better success. The subject of the invention is thus a process for the preparation of alkanephosphonic acid monoalkyl esters of the formula I. OR2 30 / R3-p ' (I), O X) H 35 in which R1 denotes alkyl groups with 4 to 22 C atoms and R2 alkyl groups with 1 to 22 C atoms, which is characterized in that monoalkyl phosphites of the formula II OR2 Hpf H\ O OH (II), 45 The addition of α-olefins to dialkyl phosphites, monoalkyl phosphites and also phosphorous acid in the presence of radical formers is known, for example from US Pat. No. 2,957,931. This process, which is carried out at reaction temperatures around 100 ° to about 150 ° C., requires long reaction times and leads to unsatisfactory yields. These are 70 to 75% of alkane compounds for the phosphites, but only about 25% of pure alkane phosphonic acid for the phosphorous acid. Overall, these yields are insufficient for technical purposes, in particular they lead to separation problems when working up the reaction products. It has already been described (cf. DOS 1.963.014) to increase the yields - while simultaneously shortening the reaction times - by using sulfur-free olefins and working at temperatures between 150 ° and 200 ° C. However, this process only relates to dialkyl phosphites, from which alkanephosphonic diesters in which R2 has the meaning given above, with sulfur-free or virtually sulfur-free α-olefins which contain 4 to 22 C atoms, in the presence of free radical formers, for example UV light Temperatures of 150 ° to 200 ° C, preferably 160 ° to 180 ° C, implemented. In the process according to the invention, the a-olefins are added to the 1-isomers in at least 95% yield, while the 2-isomers are formed only to a minor extent. Likewise, the telomerizates which often arise in large quantities in the case of analogous reactions are generally formed here only in minor quantities of at most 1 to 2% by weight. It is of no importance for the process according to the invention that the monoalkylphosphites are generally not exclusively as such at the 60 reaction temperatures used and also at room temperature, but are in equilibrium with the corresponding dialkylphosphites and phosphorous acid. You can use these monophosphites e.g. obtained in a manner known per se by esterifying phosphorous acid with a corresponding alkanol, preferably in a solvent suitable as an entrainer for the distillative removal of the water which forms, such as benzene, toluene, xylo], or more simply 4th to be brought to condensation. However, they can also be removed from the reaction mixture by distillation after the reaction has ended. The implementation time in the present method is considerably shorter than in the previously known working methods. The reaction time is generally up to about 6 hours. It is often around 3 to 5 hours. Only when using UV light irradiation is it expedient to achieve a high yield by extending the reaction times to about 7 hours. The implementation proceeds with very good yields. The method can preferably also be designed continuously. The proportion of telomerizates in the reaction product can increase slightly. The mixture of alkanephosphonic acids, alkanephosphonic acid monoesters and alkanephosphonic acid diesters obtainable according to the invention is in itself an interesting intermediate product. This mixture preferably serves as a precursor for the production of alkanephosphonic acids, which e.g. have gained importance as a mercerization or flotation aid. As already described above, the mixtures can of course also be separated into the individual constituents and the alkanephosphonic acid monoesters can be isolated. For the preparation of alkanephosphonic acids, these mixtures can e.g. be subjected to acidolysis in a manner known per se. However, hydrolysis by the process of DE-OSes 2441783 and 2441878 by reaction of the reaction mixture obtained according to the invention, which essentially consists of alkanephosphonic acid monoester, alkanephosphonic acid diester and alkanephosphonic acid, with water at temperatures of 160 ° to 300 ° C. using at least the stoichiometric is preferred required amount of water and distilling off - if appropriate together with water - the alkanol formed. The process according to the invention thus shows an economically very advantageous route for the preparation of the technically important alkanephosphonic acids, which proceeds via a partial esterification of phosphorous acid, the latter also being able to be used without difficulty in such qualities as are obtained as a by-product in a number of processes and to date technically could not be used.