CA1085870A

CA1085870A - Preparation of haloalylphosphonic acid

Info

Publication number: CA1085870A
Application number: CA287,599A
Authority: CA
Inventors: Robert J. Kiesel; David I. Randall
Original assignee: GAF Corp
Current assignee: GAF Corp
Priority date: 1976-12-20
Filing date: 1977-09-27
Publication date: 1980-09-16
Also published as: GB1592265A; BE860496A; IL53081A; JPS5377017A; BR7707294A; DE2755278A1; IL53081A0; FR2374329A1

Abstract

PREPARATION OF HALOALKYLPHOSPHONIC ACID

Abstract of the Disclosure A process for the preparation of haloalkylphosphonic acid which comprises contacting hydrogen halide with a haloalkylphosphonate of the formula:

Description

This invention relates to the preparation of haloalkyl phosphonic acids, especially the preparation of

2-chloroethyl-phosphonic acid (hereinafter CEPA) and more particularly to an improved high temperature, high pressure process for converting or cleaving bis- (2-chloroethyl~-2-chloroethyl phosphonate (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 ET~LENE IN
PLANT BIOLOCY 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)D Many uses of CEPA have been amply described in the patent, trade and scientific literature, an early such publication by Cooke and Randall (a ~5 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. Instant 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 HCl 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 involves conducting the reaction between BICEP and excess concentrated HCl under autogenous pressure in a sealed pressure reactor. This method results in gr~atly 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 ~EPHA), is charged as aqueous acid into the reactor at the start of the ; 20 reaction, a comparatively large volume of water in 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 involves incremental addition into a pressure-tight 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 100 to 145C., of sufficient HCl gas to maintain in said xeactor a super atmospheric pressure preferably ranging from about 50 to 90 psig. The illus-trative examples therein describe reactions carried out at 120C. 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 ~IC~P 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, i5 objectionable from a commercial : standpoint.
In Randall et al U.S. 3,600,435, a method is described involving reaction of BICEP with anhydrous ~Cl gas at temperatures above the 140C. and atmospheric pressures. Although this method inhibits or avoids the production of HEPHA (from hydrolysis of C3PA), it yields/
in addition to the desired CEPA, substantial amounts of the bix-(2-chloroethyl-phosphonic 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 2,148j549, processess are disclosed involving reaction of BICEP with HCl gas at temperatures up to 200C., 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 ethylene dichloride by-productr with simultaneous drop is pressure and temperature which must thus each time be raised again with addition 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.

;7~

And in Dutch Patent Application 71/16982, an anhydrous process ~s disclosed involving reaction of BICEP with anhydrous HCl gas at temperatures of lQO ~o 2Q0C. 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 ~hich~ 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 ~mount o black precipitate and a dark oily ;;
laye~
It ~ould be advantageous to have an improved process for producing CEPA which obviates one or more of the above disadvantages; e.g. a process ~nv~lving ~eaction of BIC~P and/or MEPHA with hydrogen chloride. It would ~lso be advantageous to have a process enabling larger batch sizes ~without ~ncrease or reactor size) and/or shorter reaction times and/or higher CEPA assays or purities and/or reducted im~urities therein. It would be ~u~ther advantageous to have a highly selective and economical process for the pToduction of CEPA, or corresponding haloalkyl phosphonic acids, in high yield~
The present invention provides in a process for the preparation 2Q of haloalkyl phosphonic acid, especially 2~chloroethylphosphonic acid, ~herein hydrogen halide, preferably hydrogen chloride, is contacted at a temperature of between about 110C and about 160C with a haloalkyl~
phosphonate of the formula 11~,, OR
X(C~l21n~P
O (CH2) nX

,~
L ~ 4~

wherein X is a halogen such as fluorine, chlorine, bromine or iodine;
R is h~drogen or -CCH2)nX and n is an integer of 1 to 6, preferably X is Cl and n is 2, the improvement which comprises conducting the reaction in a pres~ure~tight reactor in a closed system in the presence of from about 0~1 to 1,8 moles of water per mole of said phosphonate; controlling the water concentration within said range throughout the reaction; incrementally adding suficient dry hydrogen halide into said pressure-tight reactor containing the reaction mixture to ma;ntain a pressure of at least 100 psig therein during at least a major portion of the reaction and conducting the reaction in the absence of venting any of the contents of the reactor during reaction. Completion of the reaction results in a liquid mixture comp~ising primarily the corresponding alkyl dihalide and the haloalkyl-phosphonic acid, prefera~ly ethylene dichloride and 2~chloroethylphosphonic acid, ; Advantage~ of the present process, relative to presently employed ~,~
proces~es, generally include:
Cl~ Larger batch sizes because less aqueous HCl is introduced or is present in the reactor.
C2l CEPA purities of 90% or more.
C3) Less by~product HEP~
C4) Less unreacted MEPHA~
(5~ Shorter reaction time cycles~
(61 Shorter stripping time because less water is present.
(71 Lighter coloTed product when formulated ~or use on crops.
C8~ 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 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 BIC~P, although it is to be understood that mixtures of BICEP and MEP~A, or MEPHA alone, and/or ~F, ~Br, or HI can substituted in the following discussion. Similarly, any of the BICEP or MEPHA derivatives, within the scope of the above stru~tural formula, can be substituted where appropriate.
The process of this invention is carried out in a pressuxe-tight reactor vessel, e.g., an autoclave which is composed or lined with acid-resistant material and/or lined with a glass or porcelain or the like, 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 ~Cl gas, preferably at the bottom to assist in agitating the contents. The 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, the contents heated to about 110 to 160C., preferably about 1~5 to 145C., and dry ~Cl gas is injected under pressure to raise the pressure in the reactor to at least about 100 psig (lbs.
per square inch gauge) up to 500 or more psig, preferably ii8~

about 150 to 250, more preferably about 165 to 225 psig.
The reaction mixture is then 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 1~ initially charged to the reactor fall within the range of about Ool to 1.8 moles, preferably about 0.2 to 1.5 moles, per mole of the BICEP or related haloalkylphosphonate charged, and the water concentration is maintained within this ranqe throuqhout the reaction. The reaction theoretically requires 2 moles of HCl per mole of BICEP or related haloalkylphosphonate diester, and 1 mole of HCl when the 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 ~Cl gas injected during the reaction, it is most convenient, to hasten initiation of the reaction and the like, 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 about 23%, more preferably at least about 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 1~ 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 ~ressure 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 cooled to B~

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 separated, as by drawing off or siphoningJ 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 J 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, o-dichlorobenzene, etc. at elevated tempe~atures such as about 160C.
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 of ~-BICEP or MEPHA to produce other haloalkylphosphonic acids .. ,. . ~. .

such as for example the bromo, iodo and fluoroanalogs of CEPA, and corresponcling halopropylphosphonic, haloisopropylphosphonic, halohexylphosphonic acids and the like, preferably having halogen bonded to the terminal carbon atom of an ethyl group. Instead of BICEP or MEPHA, there may be employed the corresponding esters of haloalkylphosphonic acids such as the halogenated bis or mono -methyl, -propyl, -hexyl esters and the like~ For agricultural or other uses which may require liberation of alkene from instant acid products, the halogen is preferably bonded to the B-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 ~EPHA, MEPHA~ and/or bis-(2-chloroethyl) vinyl phosphonate, and/or lower amounts of water which must be stripped in relatively shorter reaction times and/or higher output from the available reactor equipment.
29 The following examples are only iliustrative 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 1.0~% HCl, 1.8%
water, by weight, 1.25 moles of water and a molar water:

37~

BICEP ratio of 0.28:1. The autoclave is sealed, heated to ; about 135C. with stirring, pressurized with dry HCl gas in]ected at the bottom of the autoclave to about 220 psig, and the injection continued while maintaining the reaction mixture at 135C. 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 temperature of 75C/15 mm. The CEPA so obtained is a clear, crystalline yellow product, weighs 585 g. and analyzes as follows:
CEPA 90.0% MæpHA 1.0%; HEPHA 0.3%; H3PO4 2.5~; water 0.5%.

EXAMPLE II
The procedure of Example I is repeated except that (1) the initial charge contains 150 ml. (179 g.) o 37~
aqueous HCl to provide an acid concentration of 4.8% ~Cl and 8.1% water, by weight or 6.27 moles of water to pro-vide 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 results are: 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 120C.

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 150C. and pressurized to 230 psig by injection of dry HCl gas at the bottom of the autoclave. The reaction mixture is maintained at 150C/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 75C. 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 75C./15 mm.

The CEPA so obtained is dark brown and analyzes as follows: CEPA 93 . 99~; MEPHA 3 .1%; HEPHA O .1~; H3P04 1. 0%;
H20 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 III

A one-gallon stirred, glass-lined autoclave is charged with 931.5 g. (4.5 moles) of mono-2-chloroethylphosphonate (MEPHA) and 150 ml. (179 g.) of 37~
aqueous HCl. This mi~ture contains about 5.96 weight% HCl and lQ.2 weight perrent H20 to provide a molar water MEPHA
ratio of about 1.4:1.
The autoclave is then sealed, heated to about 145C. and continuously stirred. Over a period of about 7.5 hours, the system is pressurized three times to 250 psig by injection of dry HCl 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 waterO The lower aqueous layer is then stripped of water and HCl by flash evaporation to a final drying temperature of 75.5C./15 mm.

7~
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 II 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 2-1uoroethylphosphonic 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-iodoe~hyl-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 respect to preferred embodiments and it will be understood that modifications and variations and the substitutions discussed in the foregoing specification will become obvious to those skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.

Claims

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

1. In a process for the preparation of haloalkyl phosphonic acid wherein hydrogen halide is contacted at a temperature of between about 110°C and about 160°C with a haloalkylphosphonate of the formula wherein X is a halogen such as fluorine, chlorine, bromine or iodine;
R is hydrogen or -(CH2)nX and n is an integer of 1 to 6, the improvement which comprises conducting the reaction in a pressure-tight reactor in a closed system in the presence of from about 0.1 to 1.8 moles of water per mole of said phosphonate; controlling the water concentration within said range throughout the reaction; incrementally adding sufficient dry hydrogen halide into said 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 and conducting the reaction in the absence of venting any of the contents of the reactor during 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 claim 1 wherein X is a chlorine and n is 2.

6. A process as defined in claim 5 wherein said pressure ranges from about 150 to 250 p.s.i.g.

7. A process as defined in claim 5 wherein said reactor contains about 0.2 to 1.5 moles of water per mole of said phosphonate.

8. A process as defined in claim 5 wherein said water is supplied in the form of aqueous hydrochloric acid of at least about 23% concentration before reaction is initiated.

9. 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-chloroethylphosphonic acid, and recovering said phosphonic acid from the aqueous phase.

10. A process as defined in claim 5 wherein said water is supplied in the form of aqueous hydrochloric acid of at least about 35%
concentration before reaction is initiated.

11. A process as defined in claim 1 wherein said pressure ranges from about 150 to 250 p.s.i.g.

12. A process as defined in claim 1 wherein said pressure ranges from about 165 to 225 p.s.i.g.

13. A process as defined in claim 1 wherein said water is supplied in the form of aqueous hydrochloric acid at a concentration of about 37%
before reaction is initiated.

14. A process as defined in claim 1 wherein said reactor contains from about 0.2 to 1.5 moles of water per mole of haloalkylphosphonate.

15. The process of claim 1 wherein the reaction is completed within a period of about 7.75 hours.