US3408428A - Halogenated phosphonate esters - Google Patents

Description

United States Patent 3,408,428 HALOGENATED PHOSPHONATE ESTERS Robert H. Boschan, Los Angeles, and James P. Holder,

Woodland Hills, Califi, assignors, by mesne assignments, to McDonnell Douglas Corporation, Santa Monica, Caliii, a corporation of Maryland No Drawing. Filed Dec. 28, 1964, Ser. No. 421,699

- 8 Claims. (Cl. 260-961) ABSTRACT OF THE DISCLOSURE This invention relates to certain halogenated aryl benzenephosphonate esters and is particularly concerned with the provision of novel chloro and fluoro diphenyl benzenephosphonates.

It is an object of the present invention to provide a series of compounds having high fire resistance, high temperature stability, and which remain in liquid form over a relatively wide temperature range and are relatively non-volatile at elevated temperatures.

Another object of the invention is the provision of novel fluorinated diaryl, particularly fluorinated diphenyl, benzenephosphonates and chlorinated diaryl, particularly chlorinated diphenyl, benzenephosphonates having the above-noted properties and other advantages, and having utility as hydraulic fluids, heat transfer fluids, and lubricants, particularly at elevated temperatures, and as additives for hydraulic fluids, heat transfer media and lubricants.

Other objects and advantages will appear hereinafter.

We have discovered that the above-noted objects are achieved according to the invention by the provision of a class of halogenated diphenyl benzenephosphonates having the formula:

X C II where X and X' are each a member selected from the group consisting of fluorine and chlorine, with X and X' being the same or different halogens. Preferably X and X' are the same halogen and are located in the same position, e.g., in meta or in para position, on the phenyl nucleus.

The fluorine and chlorine substituents can be carried in ortho, meta or para position on the phenyl nucleus with respect to the attachment of such nucleus to the oxygen atom of the phosphonate ester. However, the meta and para derivatives generally are preferred. Also, the bis(monofluorophenyl)benzenephosphonates are preferred over the corresponding chlorinated derivatives, as having greater stability at higher temperatures.

It has been found that the above-defined bis(halogenophenyl)benzenephosphonates are valuable as functional fluids, e.g., as base stocks for hydraulic fluids, as heat transfer media, and as lubricants, particularly at elevated temperatures, e.g., above about 120 F., due to the advantageous physical properties of such compounds, in-

3,408,428 Patented Oct. 29, 1968 eluding high fire resistance and increased temperature stability. Thus, for example, generally these fluorinated and chlorinated phosphonate esters have a thermal stability in the range of about 600 to about 800 F. and autoignition temperatures of the order of about 900 to about 1,000 F. These compounds are also relatively non-volatile at elevated temperature due to the high boiling point of these materials. Moreover, the phosphonate esters of the invention have good hydrolytic stability and do not adversely affect materials, such as metals, e.g., steel, aluminum, and the like, with which they may be in contact.

The above-noted properties render the halogenated phosphonate esters hereof useful as hydraulic fluids, lubricants and heat transfer media, e.g., cooling fluids, in aircraft systems at moderately elevated temperatures.

The difluoro, dichloro and fluorochloro phosphonate esters of the invention also can be employed as general industrial hydraulic fluids and lubricants particularly where high fire resistance and high thermal stability are important characteristics, e.g., in high pressure systems, such as hydro electric turbines, air compressors and hydraulic presses having various sources of ignition, which would result in fire and explosion from leaking hydraulic fluids in the event such fluids are not adequately fire resistant.

Also, the chloro, fluoro and fluorochloro substituted phosphonate esters according to the invention can be employed as additives, for example, in combination with each other or with compatible phosphate or phosphonate esters in which they are miscible, such as the pentafluorophenyl substituted phosphate esters of the copending application Serial No. 364,787, filed May 4, 1964, of Seil et al. or the fluorinated diaryl phosphate esters of the copending application Serial No. 364,763, filed May 4, 1964, of Seil et a]. now Patent No. 3,308,207. When so employed, the compounds of the invention can function as base stock components, thickeners, lubricity improvers, or pour point depressants in the base stock, e.g., the phosphate or phosphonate esters in which the invention compounds are incorporated. When employed as additives, the benzenephosphonate esters of the invention are used generally in a proportion of about 1 to about 10% by weight of the total composition including base stock. However, when employed as base stock components in such mixtures, the halogenated phosphonates of the invention can be employed in substantially larger amounts.

The bis(monohalogenophenyl) benzenephosphonates of the invention are produced according to one convenient mode of procedure by reacting the corresponding monohalogenated, e.g., monochloro or monofluoro phenol, or mixtures thereof, with benzene phosphonyl dichloride, in a proportion of about 2. moles of the phenol or phenols to one mole of phosphonyl dichloride, preferably in the presence of pyridine or any other suitable HCl acceptor. The proportion of HCl acceptor or pyridine generally employed is usually about equimolar with respect to the halogenated phenol. The mixture is then heated at reflux for a period of hours, and is then cooled and a relatively large volume of water added. The mixture separates into an organic phase and an aqueous phase, and the organic phase containing the phosphonate ester product is Withdrawn. The aqueous layer is extracted with a solvent such as ether to remove organic values and the ether extract is added to the main organic layer withdrawn. The remaining organic reaction mixture is washed and then dried with a drying agent such as anhydrous magnesium sulfate. Solvents are removed by distilling at reduced pressure, and the remaining mixture is distilled at still lower pressure to recover the desired bis- (monohalogenophenyl)benzenephosphonate compounds.

Where unsymmetrical phosphonate derivatives of the cunr or 3 6 F fl 7 Cl U C5 CQHfiPO F I? I 0.115? 00 The following are examples of preparation and use of the invention compounds:

EXAMPLE 1.Bis(p-fluorophenyl)benzenephosphonate To a mixture of 70.6 g. (0.630 mole) of p-fluorophenol, 52.2 g. (0.660 mole) of pyridine and 250 ml. of benzene was added dropwise with stirring 58.5 g. (0.300 mole) of benzene phosphonyl dichloride. The temperature was maintained at l3-l7 C. during the addition, which was complete in one and one half hours. The mixture was heated slowly to reflux and refluxed for 66 hours.

The mixture was then cooled and poured into 400 ml. of water. The lower aqueous layer was removed and extracted with three ml. portions of ether. The ether extracts were added to the organic layer, which was then washed with 100 ml. of 5% hydrochloric acid, 100 ml. of sodium bicarbonate, and three 75 ml. portions of water. After drying over anhydrous magnesium sulfate, the solvents were removed by heating on a steam bath. The residue was then distilled at reduced pressure; the main product fraction, 86.5 g. (83.3% yield) distilled at 184 C. (0.33 mm. mercury), M.P. 45.347.2 C. Analysis calculated for C H F O P: C, 62.44; H, 3.78. Found: C, 62.01; H, 3.76.

The resulting phosphonate ester product, bis(p-fluorophenyl)benzenephosphonate, Compound 1 above, has good thermal stability between about 600 and about 800 F., high autoignition temperature in the range of about 900 to about 1,000 F., good hydrolytic stability and high fire resistance. Such compound is useful as a base stock component for a hydraulic fluid of an aircraft system at temperatures above about F., or as a fire resistant thermally stable hydraulic fluid or lubricant for general industrial purposes, e.g., in a hydraulic press or as a compressor lubricant at moderately elevated temperatures.

EXAMPLE 2.-Bis(m-chlorophenyl) benzenephosphonate To a mixture of 35.3 g. (0.315 mole) of m-chlorophenol, 26.1 g. (0.330 mole) of pyridine, and ml. of benzene was added dropwise with stirring 29.2 g. (0.150 mole) of benzene phosphonyl dichloride. The temperature was maintained at 1016 C. during the addition, which was complete in 45 minutes. The mixture was heated to reflux and refluxed for 21 hours.

The mixture was then cooled and poured into 250 ml. of water. The lower aqueous layer was withdrawn and extracted with one 100 ml. portion and two 50 ml. portions of ether. The ether extracts were added to the organic layer, which was then washed with 100 ml. of 5% hydrochloric acid, 100 ml. of 5% sodium bicarbonate, and one 100 ml. portion and two 50 ml. portions of water. After drying over anhydrous magnesium sulfate, the solvents were removed by heating on a steam bath. The residue was then distilled at reduced pressure; the main product fraction, 32.5 g. (57.3% yield), distilled at 218 C. (1.1 mm. mercury), M.P. 62.6-64.1 C.

The resulting product consisting essentially of bis(mchlorophenyl)benzenephosphonate, Compound 2 above, has good thermal stability, high autoignition temperature, good hydrolytic stability and high fire resistance. Such phosphonate is useful as a base stock for a hydraulic fluid or lubricant in a system operating at temperatures in excess of about F.

EXAMPLE 3 .-Bis (m-fluorophenyl) benzenephosphonate To a mixture of 70.6 g. (0.630 mole) of m-fluorophenol, 52.2 g. (0.660 mole) of pyridine and 250 ml. of benzene was added dropwise with stirring 58.5 g. (0.300 mole) of benzenephosphonyl dichloride. The temperature was maintained at 1216 C. during the addition, which was complete in one hour and 40 minutes. The mixture was heated slowly to reflux and refluxed for 18 /2 hours.

The mixture was then cooled and poured into 500 ml. of water. The lower aqueous layer was withdrawn and extracted with three 100 ml. portions of ether. The ether extracts were added to the organic layer, which was then washed with 100 ml. of 5% hydrochloric acid, 100 ml. of 5% sodium bicarbonate, and three 50 ml. portions of water. After drying over anhydrous magnesium sulfate, the solvents were removed by heating on a steam bath. The crystallized residue, 66.8 g. (64.3% yield), M.P. 72.072.8 C. was recrystallized from hexane; 59.9 g. (57.6% yield), M.P. 73.173.5 C., of product were recovered.

The resulting product consisting essentially of Com- EXAMPLE 4.-m-Chlorophenyl m-fluorophenyl benzenephosphonate To 40.5 g. (0.315 mole) of m-chlorophenol, 35.3 g. (0.315 mole) of m-fluorophenol, and 52.2 g. (0.66 mole) of pyridine in 250 ml. of benzene was added dropwise with stirring 58.5 g. (0.30 mole) of benzenephosphonyl dichloride. The temperature was maintained at 20- 25 C. during the addition, which was complete in 15 minutes. The mixture was then heated and refluxed for 16 hours.

The mixture was cooled and poured into 400 m1. of water, and the upper organic layer was removed. The aqueous layer was extracted with three 100 ml. portions of ether, and the ether extracts were added to the organic layer. The organic layer was washed with successive 100 ml. portions of 5% hydrochloric acid, 5% sodium bicarbonate, and water, then with two 50 ml. portions of water. The organic layer was dried over anhydrous magnesium sulfate and filtered. The solvents were removed by evaporation on a steam bath.

The residue was filtered and 41.3 g. of solid product was obtained, M.P. 61.0-63.5 C. After three recrystallizations the product melted at 66.0-67.5 C.

The product obtained was Compound 4 above, mchlorophenyl m-fluorophenyl benzenephosphonate. Such product has good thermal stability, high autoignition temperature, good hydrolytic stability and high fire resistance, and is useful as a hydraulic fluid or component thereof.

EXAMPLE 5 A mixture is prepared consisting of 95% by weight of bis(pentafluorophenyl)butyl phosphate and 5% by weight of the compound produced in Example 1 above, his p-fluorophen-yl) benzenephosphonate.

The butyl phosphate ester noted above is described and claimed in the above copending application Serial No. 364,787 of Seil et a1. and is useful as a base stock for a hydraulic fluid of an aircraft system. The resulting mixture of this compound together with the compound of Example 1 hereof employed as additive, has the advantageous properties of the butyl phosphate ester, and in addition has improved lubricity and reduced pour point. Such mixture is eflective as a hydraulic fluid and lubricant.

EXAMPLE 6 About 92.5% of 1,1,S-trihydroperfluoropentyl diphenyl phosphate and 7.5% by weight of the compound of Ex ample 2 above, bis(m-chlorophenyl)benzenephosphonate are mixed. The diphenyl phosphate ester is described and claimed in the above copending application Serial No. 364,763 now Patent No. 3,308,207 of Seil et a1. and is indicated therein as useful as a hydraulic fluid of an aircraft system. The resulting mixture containing the additive of Example 2 above, has improved lubricity, viscosity characteristics and pour point, as compared to the diphenyl phosphate component alone of the mixture.

From the foregoing, it is seen that the invention provides a novel class of halogenated, e.g., fiuoroand/01 chloro-substituted diphenyl benzenephosphonates which are useful particularly at elevated temperature, as hydraulic fluid base stocks, or as base stock components or additives for hydraulic fluids, lubricants and heat transfer or cooling media, for aircraft systems and for industrial use.

While we have described particular embodiments of our invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. A phosphonate having the formula and selected from the group consisting of phosphonates of the above formula (a) wherein X and X are each fluorine, and (b) wherein X is fluorine and X is chlorine.

2. A phosphonate having the formula wherein X and X are each fluorine.

3. A phosphonate having the formula wherein X is fluorine and X is chlorine.

4. A phosphonate as defined in claim 1, wherein X and X' are in the same position on the phenyl nuclei.

5. A phosphonate as defined in claim 1, wherein X and X are in different positions on the phenyl nuclei.

6. Bis(p-fluorophenyl) benzenephosphonate.

7. Bis(m-fluorophenyl) benzenephosphonate.

8. m-Chlorophenyl m fluorophen-yl benzenephosphonate.

References Cited UNITED STATES PATENTS 2,769,743 11/1956 Mattson l6730 CHARLES B. PARKER, Primary Examiner. B. BILLIAN, A. SUTTO, Assistant Examiners.