CA1043350A

CA1043350A - Preparation of phosphonic and/or phosphinic acids

Info

Publication number: CA1043350A
Application number: CA234,611A
Authority: CA
Inventors: Hans-Jerg Kleiner; Walter Dursch; Horst-Dieter Thamm
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1974-08-31
Filing date: 1975-08-29
Publication date: 1978-11-28
Also published as: FR2283145B1; JPS5152130A; CH617206A5; NL7510054A; IT1042188B; FR2283145A1; JPS5850232B2; GB1526052A

Abstract

PREPARATION OF PHOSPHONIC AND/OR PHOSPHINIC ACIDS
Abstract of the disclosure:
Preparation of phosphonic and/or phosphinic acids by hy-drolytic cleavage of phosphonic and/or phosphinic acid alkyl esters in the presence of the posphonic and/or phosphinic acid by carrying out the hydrolysis at a temperature of from 170 to 300°C, in case of R5 being methyl group at a temperature of from 160 to 250°C, with the use of at least a stoichiometric amount of water, and by distilling off the alkanol formed, optionally together with water.

Description

HOE 74/~ 253 K

The present invention relates to a process for the pre-paration of phosphonic and phosphinic acids.
The processes hitherto known for the preparation of phos-phonic or phosphinic acids from the corresponding alkyl esters easily obtainable are generally carried out using mineral acids or hydrogen halides. They have many disad~antages; thus, they require special methodsfor the purification of the final product to liberate it from the mineral acids used, or they cause the formation of considerable amounts of by-products.
Another process is known according to which phosphonic or phosphinic acid alkyl esters, in the presence of the cor-responding phosphonic or phosphinic acids, are subjected to a hydrolytic splitting at temperatures of from 90 to 150C.
The reaction temperatures are expressly limited to a maximum of 150C, preferably 140C, since only up to these tempera-tures decomposition and discoloration of the products are avoid-ed. ~owever, this process so far has not been applied on an industrial scale since the necessary reaction times are too long.
Surprisingly, there has now been found a process for the preparation of phosphonic and/or phosphinic acids by sa-ponification of the corresponding phosphonic and/or phosphinic acid alkyl esters, which process overcomes the disadvantages of the known processes and gives phosphonic and/or phosphinic acids of excellent quality with practically quantitative yields.
Subject of the present invention is therefore a process for the preparation of phosphonic and/or phosphinic acids of the formula ~)

- 2 - `~

HOE 74/F 25~ g ~0433S0 R1~ ¦¦
~ P - OH (I) R

were R~ is an alkyl radical having from 1 to 20 carbon atoms, an alkenyl radical having from 2 to 20 carbon atoms, an ar-alkyl radical having from 7 to 12 carbon atoms or an aryl ra-dical having from 6 to 10 carbon atoms, these radicals optio-nally being mono- to trisubstituted, preferably monosubstitut-ed, by Cl, Br, alkyl or alkoxy groups each having from 1 to 4 carbon atoms; or R1 is a radical o~ the formula (la) - Z - P - OX (Ia~

where Z is an alkylene radical having from 2 to 6 carbon atoms, a phenylene, biphenylene, naphthylene radical or a radical or the formula (Ib) Cn H2n ~ Cn H2n (Ib) where n~ and n2 are identical or different integers of from 1 to 4, preferably n1 = n2 = 1; and R2 in the formulae (I) and (Ia) is either as defined for R1, except the radical of formula (Ia), R1 and R2 being either identical or different, or OH;
by hydrolytic cleavage of phosphonic and/or phosphinic acid 29 alkyl esters of the formula (II) ~OE 74/F 253 K
lV4;~350 R3\11 / P - oR5 (II) where R3 is as defined abo~e for R1 except the radical of f~rmula (Ia), or a radical of the formula (IIa) _ z - I - oR5 (IIa) where Z is as defined in formula (Ia) t and R4 in formulae ~II) and (IIa) is either as defined for R3 except the radical of formula (IIa), R3 and R4 being either identical or different, or oR5 or OH, R5 being a methyl group or a straight-chain or branched alkyl group having from 2 to 8, preferably from 2 to 4 carbon atoms, optionally being substituted, preferably monosubstituted, by chlorine or bromine;
in the presence of the phosphonic and/or phosphinic acid of formula (I), which comprises carrying out the hydrolysis at a temperature of from 170 to 300C, preferably from 190 to 230C, in case of R5 being a methyl group at a temperature of from 160 to 250C, preferably from 170 to 190C, with the use of at least a stoichiometric amount of water, and by distilling off the alkanol formed, optionally together with water.
The process of the in~ention is generally carried out as follows: the ester of formula (II) and from 2 to 30 weight %, preferably from 5 to 20 weight ~, relati~e to the ester, of 29 the corresponding acid of formula (I) are heated to the desir-HOE 7~/F 25~ K
lQ43350 ed reaction temperature, and then the water is added in such a manner that the reaction temperature is maintained. Also alkanol containing water may be used for the hydrolysis. A
good intermixing of the reactants is recommended.
OE course, the reaction mixture and the water may be heated simultaneously to reaction temperature with water op-tionally distilling off, and the water still required after hav-ing attained the reaction temperature may be added as indicat-ed above. It is also possible to heat the ester of formula (II) alone to reaction temperature and to add subsequently a solution of the desired amount of acid of formula (I) in the required amount of water. In case of the methyl ester of formula (II), the required amount of water may be added alone, provided that a certain induction time is taken into considera-tion which is due to the fact that the amount of catalytically actLve acid of formula (I) necessary for a rapid course of the rea tion is formed from the ester by hydrolysis only then.
The upper limit of the acid/ester ratio is set only by econo-mic considerations; anyhow it rises towards infinity with the hydrolgsis proceeding.
According to the process of the invention, the alkanol formed in the reaction is distilled off, preferably in usual manner via a distillation column or an equivalent device, option-ally in the form of an azeotropic mixture; entrained water which possibly separates in the condensation ofthe azeotropic mixture being eliminated and recycled into the hydrolysis.
As stoichiometric amount, there is required 1 mol of water for each ester group of the compound of formula (II). General-29 ly, however, it is advantageous to use an excess of water, which depends above all on the efficiency of the device used for separating the alkanol and on the amount of water entrain-ed by the azeotropic mixture. On the avera~e, in the case of industrial equipment, a water excess of from 50 to 200%, and from 10 to 50% when using the methyl ester of formula (II), above the stoichiometric amount is used. In order to accele-rate the hydrolysi~ and to complete it more rapidly, it may be advantageous to add lar~e amounts of water towards the end of the hydrolysis, so that the excess may amount to 200% and more, and up to 100% when the methyl ester of formula (II) is used. The alkanol containing water obtained may be reused for a further hydrolysis. Water excesses of more than 100% or even 200~, for example up to 300~ or more may be used with-out adversely affecting the process, but they are disadvan-tageous because the alkanol contained in the excess water, for reasons of preventing pollution, would have to be eli-minated by distillation.
The pressure to be chosen for the process of the invention is not critical, but the process is preferably carried out under atmospheric pressure. ~owever, any other pressure, especially elevated pressure, may also be applied, preferably a pressure below the vapor pressure of the water and/or the alkanol at reaction temperature.
By adding a quantity of water below the stoichiometric amount, it is possible to attain a partial hydrolysis only, so that mixtures of esters, semi-esters and/or acids are obtained.
The process may be carried out batchwise or continuously.
29 ~ The reaction temperatures are from 170 to ~00 C, prefer-ably from 190 to 230C, or from 160 to 250C, preferably from 170 to 190C when the methyl ester of formula (II) is us-ed; the reaction temperatures required rising towards the up-per limit of the intervals with increasing number of carbon atoms in the radicals Ri to R~.
Of course, the hydrolysis of the esters of formula (II) according to the process of the invention may be carried out also in the presence of other acidic catalysts, for example sulfuric or p-toluenesulfonic acid. Thus, the hydrolysis of an ester of formula (II) may be started also in the absence of an acid of formula (I), by adding first small amounts, that i~, preferably from 2 to 10 mol ~, relative to the ester of formula (II), of aqueous or gaseous HCl at reaction temperature, so that the amount of phosphonic or phosphinic acid desired for continuing the hydrolysis is produced in situ.
How?ver, the formation of the corresponding alkane chloride mus~ be taken into consideration in this case. When the methyl esters of formula (II) are used, the hydrolysis starts at re-action temperature by adding water alone. However, an espe-cially advantageous embodiment of the process of the invention is based on avoiding the use of catalysts foreign to the system, thus allowing the obtention of the desired final products in pure form and practically free from water. Contrary to the teaching of the state of the art, at the elevated temperatures of the process of the invention at which the reaction mixture cannot but dissolve small amounts of water, the hydrolysis proceeds not only with considerably increased reaction speed, but also decomposition and discoloration as described in the 29 literature are not observed.

_0 ~ 3 F.
1043;~S0 This result is ~ery surprising, especially in the case of high molecular weight products. It is also surprising that at the reaction temperatures according to the invention prac-tically no pyrophosphonic acids or anhydrides are formed and also dialkyl ethers or alkenes are formed to an insignifi-cant extent only or not at all.
As starting products of fDrmula (II~, phosphonic acid dialkyl or monoalkyl este~,phosp~linic acid alkyl esters and biphosphonic and biphosphinic acid alkyl esters are used, such as the dimethyl esters of ethanephosphonic acid, pro-panephosphonic acid, hexanephosphonic acid, octanephosphonic acid, hexadecanephosphonic acid, chloromethanephosphonic acid, p-bromobenzenephosphonic acid, the methyl esters of ocatanephosphon~c acid, methylethylphosphinic acid, methyl-octylphosphinic acid, methylvinylphosphinic acid, the di-me~hyl esters of ethane-1,2-bis-methylphosphinic acid, phenyl-ene-1,4-bis-methylphosphinic acid, benzylphosphonic acid, methylbenzylphosphinic acid methyl ester, eicosanephosphonic acid dimethyl ester, the methyl esters of methyleicosylphos-phinic or methylphenylphosphinic acid, the diethyl, dipropyl, di-n-butyl, diisobutyl, dioctyl ester of ethanephosphonic acid, the diisobutyl esters of propanephosphonic acid and octanephosphonic acid, hexanephosphonic acid diisopropyl ester, octanephosphonic di-(2-ethyl-hexyl) ester, hexade-canephosphonic acid diethyl ester, chloromethanephosphonic acid isobutyl ester, p-bromobenzenephosphonic acid diethyl ester, octanephosphonic acid isobutyl ester, methylethyl-phosphinic acid ethyl ester and -isobutyl ester, methyloctyl-29 phosphinic acid isobutyl ester and -(2-ethylhexyl) ester, the isobutyl esters of methylvinylphosphinic acid, ethane-1,2-bis-methylphosphinic acid and phenylene-1,4-bis-methylphos-phinic acid, benzylphosphonic acid diethyl ester, the iso-butyl esters of methylbenzylphosphinic acid and methylphenyl-phosphinic acid.
Mixtures of the corresponding mono- and dialkyl esters may also be used.
Preferred radicals R1 or R2 which according to formula (I) are lir~ed to the phosphorus via a direct C - P ~ond are those containing from 1 to 16, especially from 4 to ~2 car-bon atoms.
It is recommended to carry out the hydrolysis, especial-ly at the beginning of the reactior., in an inert gas atmos-phere. As inert gases, there may be used for example nitro-gen or argon or C02. The reaction may also be carried out in the presence of a high-boiling inert solvent such as o-di-chlorobenzene, dichlorotoluene, mono- or dichloroxylene.
After complete reaction, the phosphonic and phosph~nic acids obtained as crude products may be purified according to known methods; phosphonic scids may for example be recrystal-lized, phosphinic acids distilled.
Phosphonic and phosphinic acids are interesting inter-mediate products, for example for the preparation of plant protection products. Furthermore, they may be used, option-ally also in the form of their salts, as textile auxiliaries, antistatic or flame retarding agents, solutes, anti corro-sion or flotation auxiliaires.
- The following examples illustrate the invention.

HOE ~/F 25~ K

E X A M P ~ E 1:
154 g of chloromethanephosphonic acid dimethyl ester and 15.4 g of chlorome-thanephosphonic acid are heated to 165 -170C. Subsequently, with thorough agitation, a total of 70 ml of water is added dropwise within 4 hours. Methanol and water are distilled off via a distillation column. In a sub-sequent cooling trap, 11 g of dimethyl ether are collected, ~hich amount corresponds to about 25 mol ~, relative to the methanol amount theoretically obtained in the hydrolysis. The residue is 142.5 g of chloromethanephosphonic acid, correspond-ing to a yield of 100~ of the theoretical yield .
E X A M P ~ E 2:
224 g of hexadecanephosphonic acid dimethyl ester and 22.5 g of hexadecanephosphonic acid are heated to 190 - 200C
under a nitrogen atmosphere. Subsequently, with vigorous agi-~ation, a total of 80 ml of water is added dropwise with-in 5 hours. A methanol/water mixture is distilled off via a dis-tillation column, which mixture contains 38 g of methanol (90~ of the theoretical amount). In a subsequent cooling trap, a small amount of dimethyl ether is collected. The residue is 227.5 g of hexadecanephosphonic acid, solidification point about 85C, which corresponds to a 100~ yield.
E X A M P ~ E 3:
300 g of octanephosphonic acid dimethyl ester and 30 g of octanephosphonic acid are heated to 180 - 190C under a nitro~
gen atmosphere. -Subsequently, with vigorous agitation, 60 ml of water are added dropwise within 2 hours. ~he methanol formed is distilled off via a distillation column. In a sub-29 sequent cooling trap, 3 g of dimethyl ether are collected, lV43350 which corresponds to about 5 mol %, relative to the methanol amount theoretically obtained in the hydrolysis. The residue is 292 g of octanephosphonic acid, solidification point 81C, which corresponds to a yield of 100%.
wnen the same reaction is carried oui at 20ûC, the re-action time is 1.5 hours.
E X A M P ~ E 4:
65 g of benzenephosphonic acid dimethyl ester and 6.5 g of benzenephosphonic acid are heated to 180C. Subsequently, wlth vigorous agitation, 13 ml of water are added dropwise within 5 hours. The methanol formed in the reaction is distil-led off via a distillation column. In a subsequent cooling trap, 3.3 g of dimethyl ether are collected, which corre-sponds to about 20 mol %, relative to the methanol amount theoretically obtained in the hydrolysis. The residue cry-stallizes and is 61.6 g of benzenephosphonic acid, melting po:int 158 - 160C, which corresponds to a yield of 100~.
E ~ A M P ~ E 5:
61 g of methylethylphosphinic acid methyl ester and 6.1 g of methylethylphosphinic acid are heated to 180C. Subse-quently, with vigorous agitation, 10 ml of water are added dropwise within 6.5 hours. The methanol formed in the re-action is distilled off via a column. In a subsequent cool-ing trap, 1 g of dimethyl ether is collected, which corre-sponds to about 9 mol %, relati~e to the methanol amount theoretically obtained in the hydrolysis. The residue ~s 60 g of methyethylphosphinic acid (boiling point at 0.7 mm HG:
130 - 132C), which corresponds to a yield of 100~.

- 11 - , 1~)43350 E X A M P ~ E 6:
.
26.2 g of phenylene-1,4-bis-methylphosphinic acid methyl ester, 2.6 g of phenylene-1,4-bis-methylphospinic acid and 10 ml of o-dichlorobenzene are heated to 180C.. Subsequently, with vlgorous agitation, 4 ml of water are adaed dropwise within 6 hours. The methanol formed in the reaction is distil-led off via a column. In a subsequent cooling trap, a very small amount of dimethyl ether is collected. Subsequently, the dichlorobensene is distilled off in a water-jet vacuum.
26 g of phen~lene-1,4-bis-methylphosphinic acid, melting point 230C, are obtained, which corresponds to a 100~ yield.
E X A M P ~ E 7:
276 g of ethanephosphonic acid dimethyl ester are heated to 180C. Subsequently, with vigorous agitation, 80 ml of water are added dropwise within 10 hours. The methanol formed in the reaction is distilled off ~ia olumn. In a subsequent co;~ling trap, some dimethyl ether is collected. The residue is 220 g of ethanephosphonic acid, which corresponds to a yield of 100%.
E X A M P ~ E 8:
125 g of butanephosphonic acid di-n-butyl ester and 35 g of butanephosphonic acid are heated to 200C. Subsequently, with vigorous agitation, a total of 60 ml of water is added dropwise within 4.5 hours. The n-butanol and excess water are distilled off via a distillation column. In a subsequent cooling trap, 3 g of butylene are collected, which corre-sponds to about 5.5 mol ~, relative to the butanol amount theoretically obtained in the hydrolysis. The oily residue 29 is~104 g of n-butanephosphonic acid, corresponding to a 100 1~)4335(~
yield.
E X A M P ~ E 9:
._ 300 g of methyloctylphosphinic acid is~butyl ester and 30 g of methyloctylphosphinic acid are heated to 200 - 220C.
~ubsequently~ with vigorous agitation, 40 ~i Ol wa~er a;e added dropwise within 10 hours. The isobutanol and water are distilled off via a distillation column. In the distillate, isobutanol containing water separates as lower phase and is recycled into the reaction process. In a cooling trap, 2 g of isobutylene are collected, which corresponds to about 3 mol %, relative to the isobutanol amount theoretically ob-tained in the hydrolysis. The residue solidifies. 262 g of methyloctylphosphinic acid, solidifaction point 42.5C, are obtained, corresponding to a yield of 100~.
E X A M P ~ E 10:
1015 g of methylethylphosphinic acid isobutyl ester are cc~bined with 10 ml of concentrated hydrochloric acid, and with vigorous nitrogen f1ushing, the mixture is heated to 190 - 200C. At this temperature, the flushing is stopped.
Subsequently, with vigorous agitation, a total of 250 ml of water is added dropwise within 12 hours. Isobutanol and water are distilled off via a distillation column. In the distillatelisobutanol containing water separates as lower phase and is recycled into the reaction process. In a cool-ing trap, 15 g of isobutylene are collected, corresponding to about 4.5 mol %, relative to the isobtanol amount theore-tically obtained in the hydrolysis. The residue is 668 g of methylethylphosphinic acid, boiling point at 0.7 mm Hg 130 -29 132 C, which corresponds to a yield of 100%.

1~4335~;) E X A M P ~ E 11:
300 g of octanephosphonic acid diethyl ester Pnd 30 g of octanephosphonic acid are heated to 190 - 200C. Subsequently, with vigorous agitation, 160 ml o~ water are added dropwise within 5 hours. 158 g of water containing ethanol (water con-tent 34.3%) are distilled off via a distillation column, cor-responding to a yield of 95% of ethanol. The residue solidi-fies. 263 g of octanephosphonic acid, solidification point about 85C, are obtained, corresponding to yield of 100%.
E X A M P ~ E 12:
600 g of octanephosphonic acid di-isobutyl ester and 60 g of octanephosphonic acid are heated to 195 - 200C with nitro-gen flushing, which is stopped at this temperature. Subse-quently, with vigorous agitation, 260 ml of water are added dropwise within 5 hours. Isobutanol and water are distilled off via a distillation column. In a subsequent cooling trap, 41 g of isobutylene are collected, which corresponds to about 18.5 mol %, relative to the isobutanol amount theoretically obtained in the hydrolysis. The residue solidifies. 440 g of octanephosphonic acid, solidification point about 85C, are obtained, corresponding to a 100~ yield.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of a phosphonic acid, a phosphinic acid, or a mixture thereof, of the formula (I) (I) wherein R1 represents an alkyl radical having from 1 to 20 carbon atoms, an alkenyl radical having from 2 to 20 carbon atoms, an aralkyl radical having from 7 to 12 carbon atoms or an aryl radical having from 6 to 10 carbon atoms, and these radicals may be mono- to tri-substituted by chlorine, bromine, alkyl or alkoxy groups each having from 1 to 4 carbon atoms; or R1 is a radical of the formula (Ia) (Ia) wherein Z represents an alkylene radical having from 2 to 6 carbon atoms, a phenylene, biphenylene, naphthylene radical or a radical of the formula (Ib) (Ib) wherein n1 and n2 are identical or different integers of from 1 to 4, and R2 in the formulae (I) and (Ia) is either as defined for R1 except that it cannot represent the radical of the formula (Ia), R1 and R2 being either identical or different, or OH; in which a phosphonic acid alkyl ester, a phosphinic acid alkyl ester, or a mixture thereof, of the formula (II) (II) wherein R3 is as defined above for R1 except that it cannot represent the radical of the formula (Ia), or a radical of the formula (IIa) (IIa) wherein Z is as defined in formula (Ia), and R4 in formulae (II) and (IIa) is either as defined for R3 except that it cannot represent the radical of formula (IIa), R3 and R4 being either identical or different, or OR5 or CH, R5 being a methyl group or a straight-chain or branched alkyl group having from 2 to 8 carbon atoms which can be substi-tuted by chlorine or bromine; is subjected to hydrolytic cleavage in the presence of a catalyst comprising the phos-phonic acid, the phosphinic acid or the mixture thereof, of formula (I) at a temperature of from 170 to 300°C, with the proviso that when R5 represents a methyl group, the temp-erature is from 160 to 250°C, and in which the cleavage is carried out in the presence of at least a stoichiometric amount of water, and the alkanol formed is distilled off.

2. A process as claimed in claim 1 in which water is also distilled off with the alkanol.

3. A process as claimed in claim 1 in which the ester of formula (II) is used together with 2 to 30 weight % of the corresponding acid of formula (I), relative to the ester of formula (II).

4. A process as claimed in claim 1, claim 2 or claim 3 in which an excess of water of up to 200%, relative to the stoichiometric amount required, is used.

5. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out in a high-boiling inert solvent.

6. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out under an inert gas atmosphere.

7. A process as claimed in claim 1, claim 2 or claim 3 in which the phosphonic or phosphonic acid of the formula (I) required as catalyst is hydrolytically produced in situ at the reaction temperature by the addition of from 2 to 10 mol % of aqueous or gaseous hydrogen chloride, relative to the ester of formula (II), and, when R5 represents a methyl group, by the addition of water; and any resultant alkyl chloride is distilled off.

8. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out under atmospheric pressure.

9. A process as claimed in claim 1, claim 2 or claim 3 in which the reaction is carried out a temperature of from 190 to 230°C.

10. A process as claimed in claim 1, claim 2 or claim 3 in which R5 is a methyl group and the reaction is carried out at a temperature of from 170 to 190°C.