GB1592265A

GB1592265A - Preparation of haloalkylphosphonic acids

Info

Publication number: GB1592265A
Application number: GB47119/77A
Authority: GB
Original assignee: GAF Corp
Current assignee: GAF Corp
Priority date: 1976-12-20
Filing date: 1977-11-11
Publication date: 1981-07-01
Also published as: FR2374329A1; BE860496A; DE2755278A1; IL53081A0; JPS5377017A; BR7707294A; CA1085870A; IL53081A

Description

(54) PREPARATION OF HALOALKYLPHOSPHONIC ACIDS (71) We, GAF CORPORATION, a corporation organized and existing under the laws of the State of Delaware, United States of America, having its main office at 140 West 51st Street, New York, New York 10020, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the preparation of haloalkyl phosphonic acids, especially the preparation of 2-chloroethylphosphonic acid (hereinafter CEPA) and more particularly (but not exclusively) to an improved high temperature, high pressure process for converting or cleaving bis-(2-chloroethyl) 2-chloroethylphosphonate (hereinafter BICEP) and/or mono-(2-chloroethyl) 2-chloroethylphosphonate (hereinafter MEPHA) into CEPA.

CEPA is well known to be a valuable plant hormone producer and regulator having uses similar to ethylene as a plant growth regulant, which uses are widely published in the literature and reference texts, e.g., see ETHYLENE IN PLANT BIOLOGY by F.B.

Ables, Academic Press, 1973. Accordingly, CEPA is highly useful for hastening maturation and increasing crop yields of many fruits and vegetables, including for example soybeans, pineapples, bananas, cherries, apples, peaches, pears, oranges, lemons, peas, beans and tomatoes, as well as plant regulant uses disclosed in U.S. patent 3,879,188 and has been found to increase yields of latex from rubber trees and the like (J. Rubber Research Institute of Malaya, Vol. 20, part 5, pp 292-305, 1968). Many uses of CEPA have been amply described in the patent, trade and scientific literature, an early such publication by Cooke and Randall (a coinventor herein) appearing in Nature, Vol. 218, p.974, 1968. The corresponding fluoro, bromo and iodo derivatives of CEPA also have effects on plant life as disclosed in U.S. Patent 3,879,188. The present products are also useful flame retardants as disclosed in U.S. Patent 3,370,029.

Many known procedures for preparing CEPA have generally not been entirely satisfactory from the standpoint of economy, efficiency, and/or product purity and!or yield.

One known procedure involves conversion of tris-(2-chloroethyl) phosphite to BICEP and to CEPA with aqueous HCI under about atmospheric pressure (see Akademiya Nauk SSR Izvestiya, Otdelenie Khim, Nauk, 1946, pages 403-410). The yields and product purity from this process are too low for it to be considered commercially useful.

Still another method described in Randall et al U.S. 3,787,486 and our corresponding British Specification 1324440 involves conducting the reaction between BICEP and excess concentrated HC1 under autogenous pressure in a sealed pressure reactor. This method results in greatly improved yields and product purity; however, the extended reaction time employed has somewhat restricted its use as a commercial process. Also, since the excess HCl reactant, which aids in inhibiting formation of 2-hydroxyethylphosphonic acid (hereafter HEPHA), is charged as aqueous acid into the reactor at the start of the reaction, a comparatively large volume of water is inherently present, leading to some inefficiency in the size of the reactor and the need for acid resistant separating equipment for recovery of substantially pure product.

Another improved method described in Randall et al., U.S. 3,808,265 and our corresponding British Specification 1365809 involves incremental addition into a pressuretight reactor containing BICEP, preferably in the presence of aqueous HCl of at least 23% concentration and at least 2 moles of water per mole of BICEP and at a temperature of about 100C to 145"C., of sufficient HCl gas to maintain in said reactor a superatmospheric pressure preferably ranging from about 50 to 90 psig. The illustrative examples therein describe reactions carried out at 1200C. and pressures of 90 psig or less and indicate that as the ratio of aqueous HCl to BICEP decreases (the molar ratio of water to BICEP decreasing from 12.5:1 to 3.5:1), the reaction time increases so that completion of the reaction requires a comparatively long time, which, as pointed out above, is objectionable from a commercial standpoint.

In Randall et al U.S. 3,600,435, a method is described involving reaction of BICEP with anhydrous HCl gas at temperatures above 140"C. and atmospheric pressures. Although this method inhibits or avoids the production of HEPHA (from hydrolysis of CEPA), it yields, in addition to the desired CEPA, substantial amounts of the bis-(2-chloroethylphosphonic acid) anhydride (CEPAA), thus somewhat diluting the strength of the desired acid.

In German Patent 2,061,610 and Additions thereof, 2,134,346 and 2,148,549, processes are disclosed involving reaction of BICEP with HCl gas at temperatures up to 2000C., and pressures of 1 to 10, preferably 3 to 6, atmospheres in the presence of 0.1 to 31% of water, optionally in the form of aqueous HCl acid, but in all such processes the reactor is continuously, or repeatedly vented to distill off the ehtylene dichloride by-product, with simultaneous drop in pressure and temperature which must thus each time be raised again with additional HCl gas and heat. The expense of acid resistant distillation and reactor equipment, including control valves and the like, prohibits its general adoption as a commercial process.

And in Dutch Patent Application 71/16982, an anhydrous process in disclosed involving reaction of BICEP with anhydrous HC1 gas at temperatures of 100 to 200"C and excess pressures of 2 to 25, preferably 6 to 20, atmospheres. It has been determined that such a process obtains relatively low yields and produces an unduly darker colored CEPA product which, when employed in a formulation containing 24.5% CEPA, 32% propylene glycol and 43.5% water for use on crops, results in a dark colored product containing a considerable amount of black precipitate and a dark oily layer.

It is an object of this invention to provide an improved process for producing CEPA and other haloalkylphosphonic acids which obviates or ameliorates one or more of the above disadvantages.

According to this invention there is provided a process for the preparation of a haloalkylphosphonic acid, especially 2-chloroethylphosphonic acid which comprises contacting in a closed system a hydrogen halide, preferably hydrogen chloride, with a haloalkylphosphonate of the formula:

wherein Y is a straight or branched chain alkyl group of 1 to 6 carbon atoms with a single substituent thereon, which substituent is a halogen atom, viz. fluorine, chlorine, bromine or iodine, and R is hydrogen or Y, in the presence of from 0.1 to 1.8 moles of water per mole of said phosphonate, which concentration of water is maintained throughout the reaction and which process includes incremental addition, at a temperature of between 110 and 1600C of sufficient dry hydrogen halide, preferably HCl, into a pressure-tight reactor containing the reaction mixture to maintain a pressure of at least 100 psig therein during atleast a major portion of the reaction. Completion of the reaction results- in a liquid mixture comprising primarly the corresponding alkylene dihalide and the haloalkylphosphonje 'acid.

Preferably Y is -CH2CH2Cl so that the starting haloalkyl-phosphonate is BICEP or MEPHA. Then, if the hydrogen halide is HCl completion of the reaction results in a liquid mixture comprising primarily ethylene dichloride and 2-chlorethylphosphonic acid (CEPA).

The present invention makes possible larger batch sizes (without increase of reactor size) and/or shorter reaction times and/or (where Y is - CH2CH2Cl) higher CEPA assays or purities and/or reduced impurities therein. At least preferred processes embodying the present invention can provide a highly selective and economical method for the production of CEPA, or corresponding haloalkylphosphonic acids, in high yield.

Specifically, advantages of the present process when used for producing CEPA, relative to presently employed processes, generally include: (1) Larger batch sizes without increase of reactor size because less aqueous HCl is introduced or is present in the reactor.

CEPA purities of 90% or more.

23 Less by-product HEPHA Less unreacted MEPHA Shorter reaction time cycles.

6 Shorter stripping time because less water is present 7 Lighter colored product when formulated for use on crops.

8 Elimination of acid resistant pressure release valves and refluxing equipment.

The improved results attainable by the process of this invention are attributable to the use of limited proportions of water, which appears to catalyze the reaction, in conjuction with increased HCl pressures, which are substantially maintained by avoiding venting of the reactor during the reaction and hence avoiding detrimental effects associated with sharp pressure drops in the system.

For simplification of the description, the following discussion is drawn to the reaction of HCl with BICEP, although it is to be understood that mixtures of BICEP and MEPHA, or MEPHA alone, and/or HF, HBr, or HI can be substituted in the following discussion.

Similarly, any of the BICEP or MEPHA derivatives, within the scope of the above structural formula, can be substituted where appropriate.

The process of this invention is carried out in a pressure-tight reactor vessel, e.g., an autoclave which is composed of or lined with acid-resistant material and/or lined with glass or porcelain, and provided with means for agitating and for controlling the temperature of the contents (heating and cooling), for charging BICEP and water and/or aqueous HCl, and for injecting HC1 gas, preferably at the bottom to assist in agitating the contents. Suitably BICEP and the water and/or aqueous HCl or aqueous BICEP solution are initially charged, in any order, to the reactor which is then sealed after which the contents are heated to 1100 to 1600C., preferably 125 to 145oC., and dry HCl gas is injected under pressure to raise the pressure in the reactor to at least 100 psig (lbs. per square inch gauge) up to 500 or more psig, preferably 150 to 250, more preferably 165 to 225 psig. Suitably then, the reaction mixture is maintained with stirring at such elevated temperatures with incremental (continuous or intermittent) addition of sufficient dry HCl gas to maintain such pressures in the reactor during at least a major portion, preferably the entire portion, of the reaction.

For the attainment of the desired improved results, it is highly important that the amount of water initially charged to the reactor fall within the range of 0.1 to 1.8 moles, preferably 0.2 to 1.5 moles, per mole of the BICEP or related haloalkylphosphonate charged, and that the water concentration is maintained within this range throughout the reaction. The reaction theoretically requires 2 moles of HCl per mole of BICEP or related haloalkylphosphonate diester, and 1 mole of HCl when a monoester is employed as the reactant to produce the corresponding CEPA or related acid. Although all of the required HCl could be supplied by the dry HCl gas injected during the reaction, it is most convenient, e.g. to hasten initiation of the reaction, to charge the above-described controlled proportions of water, in accordance with this invention, in the form of aqueous HCl, preferably in concentrated form of at least 23%, more preferably at least 35%, and most conveniently about 37%, by weight. Illustratively, addition of sufficient 37% aqueous HCl to provide an initial BICEP reaction mixture containing about 0.6 to 10% water (and 0.4 - 6% HCl) supplies the 0.1 to 1.8 moles of water per mole of BICEP in the mixture, as required in accordance with this invention and provides a portion of the HCl needed for the reaction.

Subsequently, the pressure in the reactor can be maintained with dry HCl gas or with dry HCl gas together with a small amount of concentrated aqueous acid, e.g., of 37 weight percent or more acid concentration, provided the 1.8 moles of water is not exceeded.

The addition of the dry pressurized HCl gas during the reaction can be controlled manually or automatically. For example, the addition may be triggered to inject the gas when the pressure falls to a predetermined lower value within the required range and the injection stopped when the pressure has risen to a predetermined upper value within the required range. Cessation of the reaction is indicated by failure of the pressure to drop to or towards said lower value. Alternatively, the addition may be controlled to inject the gas continuously at a rate approximating its rate of reaction at the predetermined pressure in the reactor. Cessation of the reaction is indicated in this system by a rise in the pressure as the injected gas remains unreacted and builds up in the reactor. Operation of the reaction within the above-described ranges of HCl gas pressure automatically and inherently maintains the concentration of water in the reaction medium at the above-described concentrations.

The reaction is generally completed in as little as about 6.5 hours. Lowering the reaction time much below 6 hours has a diminishing effect on cost reduction because of fixed, rather long heat-up and cool-down cycles. Upon completion of the reaction, the liquid reaction medium containing mostly CEPA and ethylene dichloride is preferably cooled to obtain a two-phase system consisting of an organic phase containing the ethylene dichloride and an aqueous phase containing the desired CEPA. The two phases or layers are then separated, as by drawing off or siphoning, and the aqueous phase stripped of water and HCl as by flash evaporation under reduced pressure to obtain the CEPA in good yield and in a substantially pure state.

In cases where MEPHA replaces BICEP, in whole or in part, as a starting material in the reaction, temperature and pressure conditions within the upper portion of the above ranges can be employed.

In carrying out the present process, the BICEP reactant may be essentially pure or in crude form of from about 75-95% concentration in admixture with undistillable substances as produced in known manner by isomerization of tris-(2-chloroethyl) phosphite in the presence of an inert organic diluent such as cumene, xylene, or o-dichlorobenzene, at elevated temperatures such as about 1600C. Such isomerization reactions in the presence of a diluent are further described in many literature sources, e.g., see German Patent Specification 964,046 of March 16, 1957, incorporated herein by reference. The tris-(2-chloroethyl) phosphite is likewise obtained in known manner from phosphorus trichloride and ethylene oxide, e.g., see Kabachnik et al., C.A. 42, 7241-3, also incorporated herein by reference.

As indicated above, although the process of this invention has been described with respect to the conversion of BICEP to CEPA, the invention is operative with and inclusive of the use of related homologs and analogs (as hereindefined) of BICEP or MEPHA to produce ofher haloalkylphosphonic acids such as for example the bromo, iodo and fluoroanalogs of CEPA and of the corresponding halopropylphosphonic, haloisopropylphosphonic and halohexylphosphonic acids, preferably having halogen bonded to the terminal carbon atom of an ethyl group. Instead of BICEP or MEPHA, there may be employed other corresponding esters of haloalkylphosphonic acids such as the halogenated bis or mono -methyl, -propyl, and -hexyl esters. For agricultural or other uses which may require liberation of alkene from the acid products, the halogen is preferably bonded to carbon atoms. Still other uses may call for halo-substitution in other positions of the alkyl group.

The present invention enables the production of better yields of purer CEPA containing lower amounts of impurities such as HEPHA, MEPHA, and/or bis-(2-chloroethyl) vinyl phosphonate, and/or lower amounts of water which must be stripped production being possible in relatively shorter reaction times and/or with higher output from the available reactor equipment.

The following examples are only illustrative of this invention and are not to be regarded as limitative. All amounts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

Example I A one-gallon stirred glass-lined autoclave is charged with 1212 g. (4.5 moles) of bis-(2-chloroethyl) 2-chloroethylphosphonate (BICEP and 30 ml. (35.7 g.) of 37% aqueous HCl. This mixture contains about 1.06% HCl, 1.8% water, by weight, 1.25 moles of water and a molar water: BICEP ratio of 0.28:1. The autoclave is sealed, heated to about 135"C. with stirring, pressurized with dry HCl gas injected at the bottom of the autoclave to about 220 psig, and the injection continued while maintaining the reaction mixture at 135"C. and 220 psig until the reaction is completed in about 7 hours (at which time the pressure ceases to fall after injection of HCl gas). The reaction mixture is then cooled and discharged from the autoclave. The upper layer containing ethylene dichloride is separated from the resulting two-phase liquid system and the lower aqueous phase containing the CEPA is stripped of water and HCl by flash evaporation to a final drying temperaure of 75"C/15 mm. The CEPA so obtained is a clear, crystalline yellow product, weighs 585 g. and analyzes as follows: CEPA 90.0% MEPHA 1.0%; HEPHA 0.3%; H3PO4 2.5%; water 0.5%.

Example -Il The procedure of Example I is repeated except that (1) the initial charge contains 150 ml.

(179g. of 37% aqueous HC1 to provide an acid concentration of 4.8to HC1 and 8.1% water, by weight or 6.27 moles of water to provide a molar water: BICEP ratio of 1.4:1, and (2) the reaction mixture is pressurized with dry HCl gas at 185 psig for 7 hours. The product analyses as CEPA 92.3%; MEPHA 1.1%; HEPHA 0.5%; H3PO4 1.5%; water 0.7%.

By way of comparison, the following table summarizes the inferior results involving processes carried out with higher water: BICEP molar ratios and pressures of 70-90 psig at 1200C.

TABLE A - COMPARATIVE Moles Reaction water time CEPA MEPHA HEPHA BICEP hrs. % % 12.5 14 87.7 1.8 2.4 9.4 14 86.7 1.6 0.6 3.5 24 87.2 3.0 0.7 Further, when the CEPA obtained in accordance with the products of TABLE A are employed in a formulation containing 24.5% CEPA, 32% propylene glycol and 43.5% water for use on crops, the formulation ranges in color from yellow to dark amber and from 0-200 ppm (based on CEPA) of black material precipitates on standing 24 hours or more.

Similar formulations prepared with the CEPA produced by the process of this invention are light yellow in color and no precipitate forms on standing.

Comparative Example - Anhydrous A one-gallon stirred glass-lined autoclave is charged with 1212 g. (4.5 moles) of anhydrous BICEP. The autoclave is sealed, heated to 1500C. and pressurized to 230 psig by injection of dry HCl gas at the bottom of the autoclave. The reaction mixture is maintained at 1500C/230 psig with HCl gas injection until the reaction is complete in about 10 hours.

The reaction mixture is then discharged and cooled, the CEPA solidifying. The mixture is heated to 750C. and an aliquot of both the ethylene dichloride and CEPA is removed. The ethylene dichloride is distilled and the CEPA is dried to a final drying temperature of 75"C./15 mm.

The CEPA so obtained is dark brown and analyzes as follows: CEPA 93.9%; MEPHA 3.1%; HEPHA 0.1%; H3PO4 1.0%; H2O 0;4%.

A formulation containing 24.5% of this CEPA, 32% propylene glycol and 43.5% water is dark in color and on standing a precipitate of dark specks and a dark oily layer are formed.

Example 111 A one-gallon stirred, glass-lined autoclave is charged with 931.5 g. (4.5 moles) of mono-(2-chloroethyl) 2-chloroethylphosphonate (MEPHA) and 150 ml. (179 g.) of 37% aqueous HC1. This mixture contains about 5.96 weight% HC1 and 10.2 weight percent H2O to provide a molar water: MEPHA ratio of about 1.4:1.

The autoclave is then sealed, heated to about 145 C. and continuously stirred. Over a period of about 7.5 hours, the system is pressurized three times to 250 psig by injection of dry HC1 gas through an acid inlet valve positioned in the bottom of the reactor. After about 7.75 hours, the reaction is complete and the reaction mixture is cooled and discharged from the autoclave.

Two liquid phases are formed and the upper liquid layer containing ethylene dichloride is decanted from the lower aqueous layer containing CEPA and water. The lower aqueous layer is then stripped of water and HCl by flash evaporation to a final drying temperature of 75.5"C./15 mm.

The CEPA product is a substantially colorless, clear crystalline material weighing about 580 g. and having the following analysis: CEPA 95.0%; MEPHA 1.5%; HEPHA 0.3%; H3PO4 2.5% and water 0.5%.

Example IV The above reaction of Example III is repeated except that an equivalent amount of mono-(2-fluoroethyl) 2-fluoroethylphosphonate is substituted for MEPHA and an equivalent amount of HF is substituted for HCl. Accordingly, the product obtained is 2-fluoroethylphosphonic acid in good yield and in a high state of purity.

The same results and good yield of the corresponding acid product are achieved when mono-2-bromoethyl)-2-bromo-ethylphosphonate or mono-(2-iodoethyl) 2- iodoethylphosphonate is substituted for MEPHA and the corresponding hydrogen halide, e.g., HBr or HI, is substituted for HCl or HF in Examples III or IV; or when bis 2-fluoroethyl) 2-fluoroethylphosphonate, bis(2-iodoethyl) 2-iodoethylphosphonate or bis(2-bromoethyl) 2-bromoethylphosphonate is substituted for BICEP and the corresponding hydrogen halide, e.g., HF, HI or HBr is substituted for HCl in Example I.

This invention has been disclosed with particular reference to preferred embodiments and it will be understood that modifications and variations and the substitutions discussed in the foregoing may be made within the scope of the following claims.

Attention is directed to the claims of our UK Patents 1324440 and 1365809.

WHAT WE CLAIM IS: 1. A process for the preparation of a haloalkylphosphonic acid which comprises contacting in a closed system a hydrogen halide with a haloalkylphosphonate of the formula:

wherein Y is a straight or branched chain alkyl group of 1 to 6 carbon atoms with a single substituent thereon, which substituent is a halogen atom, and R is hydrogen or Y, in the presence of from 0.1 to 1.8 moles of water per mole of said phosphonate, which concentration of water is maintained throughout the reaction gnd which process includes incremental addition, at a temperature of between 110 C and 1600C of sufficient dry hydrogen halide into a pressure-tight reactor containing the reaction mixture.to maintain a pressure of at least 100 psig therein during at least a major portion of the reaction.

2. A process as defined in claim 1 wherein said haloalkylphosphonate is a monoester.

3. A process as defined in claim 1 wherein said haloalkylphosphonate is a diester.

4. A process as defined in claim 1 wherein said haloalkylphosphonate is a mixture of mono-and di-ester.

5. A process as defined in any one of the preceding claims wherein Y is -CH2CH2Cl.

6. A process as defined in claim 5 followed by the steps of cooling said liquid to obtain a two-phase system consisting of an organic phase containing the ethylene dichloride and an aqueous phase containing the 2-chloro-ethylphosphonic acid, and recovering said phosphonic acid from the aqueous phase.

7. A process as defined in any one of the preceding claims:wherein said pressure is maintained in the range 150 to 250 psig.

8. A process as defined in any one of the preceding claims wherein said pressure is maintained in the range 165 to 225 psig.

9. A process as defined in any one of the preceding claims wherein said reactor contains from 0.2 to 1.5 moles of water per mole of said phosphonate.

10. A process as defined in any one of the preceding claims wherein said water is supplied in the form of aqueous hydrochloric acid of at least 23% concentration before reaction is initiated.

11. A process as defined in claim 10 wherein said water is supplied in the form of aqueous hydrochloric acid of at least 35% concentration before reaction is initiated.

12. A process as defined in claim 11 wherein said water is supplied in the form of aqueous hydrochloric acid at a concentration of about 37% before reaction is initiated.

13. A process according to claim 1 for the preparation of haloalkylphosphonic acid, substantially as herein described with reference to any one of the Examples.

14. Haloalkylphosphonic acid when prepared by a process according to any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. mono-2-bromoethyl)-2-bromo-ethylphosphonate or mono-(2-iodoethyl) 2- iodoethylphosphonate is substituted for MEPHA and the corresponding hydrogen halide, e.g., HBr or HI, is substituted for HCl or HF in Examples III or IV; or when bis 2-fluoroethyl) 2-fluoroethylphosphonate, bis(2-iodoethyl) 2-iodoethylphosphonate or bis(2-bromoethyl) 2-bromoethylphosphonate is substituted for BICEP and the corresponding hydrogen halide, e.g., HF, HI or HBr is substituted for HCl in Example I. This invention has been disclosed with particular reference to preferred embodiments and it will be understood that modifications and variations and the substitutions discussed in the foregoing may be made within the scope of the following claims. Attention is directed to the claims of our UK Patents 1324440 and 1365809. WHAT WE CLAIM IS:

1. A process for the preparation of a haloalkylphosphonic acid which comprises contacting in a closed system a hydrogen halide with a haloalkylphosphonate of the formula: