Patented June 20, 1950 2,512,582

UNITED STATES2,512,582 PATENT OFFICE MIXED ALKYL BENZYL PHOSPHATES AND THEIR PRODUCTION Edwin P. Plueddemann, Woodbridge, N.J., as signor to Food Machinery and Chemical Cor poration, a corporation of Delaware . . . . . No Drawing. Application March 22, 1946, Serial No. 656,541 . 12 Claims. (C. 260 2 This invention relates to mixed alkyl benzyl the intermediate alkyl acid phosphates by the phosphates, and more particularly, to substan reaction of phosphorus pentoxide with about tially neutral tertiary alkyl benzyl-esters of phos ithree mols of the desired alcohol. phoric acid wherein the alkyl chain contains at product is, approximately an equimolarThe resultingmixture least, three and preferably at least four carbon 5 atoms. {of ... monoalkyl and dialkyl acid, phosphates. In the past trialkyl phosphates and tribenzyl these acid phosphates may be neutralized with phOSphates were generally prepared by the reac an alkaline material such as sodium hydroxide tion of trisilver phosphate with an appropriate 'or potassium hydroxide to give a thick paste of alkyl halide or a benzyl halide. Such reactions 10 , the alkali salts containing about 20 per cent have proven to have a number of industrial dis-, 'water. The acid, phosphates may also be dis advantages. I have tried to form benzyl phos Solved in a suitable solvent before neutralization phates by reacting alkali phosphates such as to give a more nobile mixture. A portion of the tripotassium phosphate, or dipotassium... acid Water may then be removed by simple distillation phosphate with benzyl chloride. Such attempts or as an azeotrope with the solvent employed. have been entirely unsuccessful. When such re An excess of a benzyl halide, advantageously actions were attempted, practically no reaction benzyl chloride, is then added and the mixture took place under mild conditions, and undermore warmed with stirring until precipitation of alkali vigorous conditions, the benzyl chloride either de chloride is substantially complete. A wide range composed or polymerized, thereby precluding the 20 of reaction conditions is possible, but in the pres Successful formation of tribenzyl phosphate. :ence of large quantities of water and at tempera In more recent times trialkyl phosphates have tures below about 120° C. the desired reaction been prepared more conveniently by the reaction proceeds slowly and the reaction time required is of phosphorus oxychloride with aliphatic alco -excessive... I have found that temperatures of 120 to 170. C. are especially well suited for the hols under carefully controlled conditions. Sev 25 reaction aithough even higher temperatures may eral of the trialkyl phosphates have been pre be used if desired. For example, the reaction pared. On a commercial Scale in this manner, may be completed at 180°. C., the reflux tempera Certain alcohols, however, such as the tertiary ture of benzyl chloride. ... aliphatic alcohols are unsuitable for the prepa Under all reaction conditions. I have observed ration of neutral esters by this method because 30 that benzyl chloride enters, into side reactions of the great sensitivity of the ester linkages to with water, solvent, or other materials with the decomposition in the presence of the hydrogen liberation of hydrogen chloride. The hydrogen chloride formed as one of the products of the chloride immediately liberates alkyl acid phos reaction. Benzyl alcohol, for this application, phates from their salts and thus interferes with more closely resembles the tertiary than the gri 35 the reaction of these salts with benzyl chloride. Inary aliphatic alcohols. Even under carefully At higher temperatures the liberated acid phos Controlled conditions the major products obtained phates decompose and are periananently lost to from the reaction of benzyl alcohol with phos the reaction. At lower... reaction temperatures phorus oxychloride are benzyl chloride and acid this decomposition is less serious and the lib phosphates. If one attempts to prepare mixed 40 erated acid may be neutralized by occasional alkyl benzyl phosphates by the reaction of alkyl additions of alkali in Small portions. I have chlorophosphates with benzyl alcohol, a large found, however, that it is possible to run the proportion of benzyl chloride and acid phosphates esterification reaction in the presence of an ex are formed and Only a poor yield of the neutral cess of alkali carbonate. The carbonate is essen mixed esters can be recovered, - v. 45 tially inert, to the alkylphosphates and to benzyl I have now discovered that neutral alkyl benzyl i. chloride, but will react, with acid materials as phosphates may be obtained in good yield, from they are liberated, thus maintaining a neutral or the reaction of a benzyl halide with the alkali slightly alkaline medium. In the presence of an salts of organic acid phosphates. This reaction excess of alkali carbonate I have found that sub may be effected at elevated temperatures by 50 stantially, no decomposition of organic phos warming the reactants together in the presence , phates in the reaction mixture results...even at of a suitable liquid solvent or diluent medium temperatures up to 180° C. A method is there such as an Organic Solvent. Or water or a com fore available for condensing benzyl-chloride with bination of the two. the alkyl-phosphate salts at a temperature at When preparing mixed alkyl benzyl phps. which a rapid reaction may be obtained. phates, I have found it advantageous to prepare Solvents may be employed to aid in bringing 2,512,582 4 3. gone substantially to completion in four to five the alkyl phosphate salts and benzyl chloride into hours. The observed difference in reactivity is contact. Choice of a solvent with an appropriate probably due to the lesser solubility of the lower boiling range also aids in controlling the reaction alkyl phosphate salts in the organic phase of the temperature. Preferred solvents for the reac reaction mixture, and to the greater... ease of tion are organic liquids boiling at a temperature hydrolysis of the lower alkyl phosphates in the above about 120° C. that are miscible with benzyl presence of water. chloride and that act at least as partial solvents At the end of the reaction period, the reaction for the alkyl phosphate salts. The solvent also mixture may be washed and the lights removed should be relatively unreactive with benzyl by distillation or the mixture may be filtered to chloride. Among such solvents are ketones, O remove alkali chloride and the organic fraction alcohols, and esters. Secondary and tertiary distilled directly from a Small excess of Solid base alcohols normally are more suitable than the to recover the mixed alkyl benzyl phosphates. primary alcohols. A particularly appropriate Normally the distillation is preferably carried solvent for the preparation of a given alkyl ben out at subatmospheric pressures. Due to the zyl phosphate is the trialkyl phosphate corre 5 mixed nature of the product and due to the sponding to the starting alkyl acid phosphate. tendency for radical interchange during pro For example, tributyl phosphate is an outstand longed heating, it is usually not practicable to ing reaction medium for the preparation of butyl fractionate the product to obtain pure separate benzyl phosphates from benzyl chloride and salts fractions of benzyl, dialkyl phosphate' and di of acid butyl phosphate. Any side reaction be 20 benzyl monoalkyl phosphate, but purified frac tween benzyl chloride and the solvent, in this tions can be obtained by exercising special Con case, serves only to produce more butyl benzyl trols and by distilling over a narrow temperature phosphates. An excess of benzyl chloride may range. Some tribenzyl phosphate is also formed also serve as solvent in the presence of a Small during the reaction and distillation, and may re quantity of water. The alkali phosphates are 25 main as a high boiling residue. Tribenzyl phos not readily soluble in benzyl chloride, but do phate itself generally decomposes, before it can come into enough contact for reaction, probably be distilled even under a good vacuum, but it by emulsification, in the presence of water. may readily be recovered if it is present in ap After a portion of the alkyl phosphate Salts have preciable quantities by recrystallization from the reacted, the esters formed serve as a sufficient 30 solvent and the water may be substantially re still residue after removal of more volatile mate moved while the reaction is completed. rials.The Substantially neutral or neutral high boil Various materials have been found to act ing mixture of alkyl monobenzyl, alkyl dibenzyl, catalytically in aiding the reaction of benzyl and tribenzyl phosphates and other complex ben chloride with alkyl phosphate salts. Among zyl phosphates obtained herein is included in these are iodides and other salts of mercury, the term mixed alkyl benzyl phosphates. Such copper, lead, and silver, as well as pyridine, mixtures have commercial value as a high boil trialkyl amines, and other organic amines and ing solvent or plasticizer. Material distillable bases. Fairly complete reaction may be obtained within a more narrow temperature range may even in the absence of these catalysts, but their 40 be separated if desired, but ordinarily no chem presence shortens the necessary reaction time ically pure compounds need be isolated. and increases the yield of alkylbenzyl phosphates The mixed alkyl benzyl phosphates of this in recovered. Catalysts for the desired condensa vention, particularly those containing from three tion also catalyze side reactions of benzyl chlo carbon atoms up in the alkyl chain and espe ride with resulting liberation of hydrogen chlo 45 cially those containing from four to eight carbon ride. In the absence of excess alkali carbonate atoms in the alkyl chain, have decided advan this increased rate of acid formation in the tages when compared to the most nearly analo presence of catalysts may actually result in a gous prior art compounds. For instance, when lower yield of neutral ester than in an uncata.- ... the preferred mixed alkyl benzyl phosphates are lyzed reaction. The full value of catalytic ac 50 used as plasticizers, they have superior charac tivity, however, may be utilized with safety in the teristics when compared to tribenzyl phosphate, presence of an alkaline carbonate. tricresyl phosphate, or trialkyl phosphates. My I have found numerous metal salts of alkyl mixed alkyl benzyl phosphates have improved acid phosphates, especially alkali metal salts, compatibility With certain resins when compared will react with benzyl chloride to form alkyl 55 with any of the mentioned prior art compounds, benzyl phosphates, but I have found that potas Ordinarily my mixed alkyl benzyl phosphates, as sium salts are particularly satisfactory. For ex compared to tribenzyl phosphate, have: greater ample, their rate of reaction and the yields of thermal stability, greater compatibility, lower neutral esters obtained are greater than has been melting points, and maintain flexibility in plas observed with sodium salts. However, sodium or 60 ticized materials at much lower temperatures. other alkali salts may be employed in the manner Generally Speaking, when a comparison is made hereinI have described. surprisingly observed that the salts con with the corresponding trialkyl phosphates, my taining longer alkyl groups react more readily products have higher flash points, decreased oil than those containing shorter alkyl groupS. So 65 extractability, and decreased volatility. My dium or potassium phosphates themselves under products are substantially completely resistant to go substantially little reaction with benzyl chlo alkaline hydrolysis and much more resistant than ride under the conditions herein described. Salts tricresyl phosphate. They are also much more of methyl and ethyl acid phosphates are decid resistant to discoloration by light than the tri edly sluggish in their reaction. Salts of propyl 70 cresyl phosphate. , . acid phosphates are still somewhat sluggish in A large number of mixed alkyl benzyl phos their reaction, but such salts as potassium butyl phates may be prepared by numerous variations phosphates and potassium octyl phosphates react of the general process outlined above, and in much more readily. A typical catalyzed reaction order to illustrate this invention more clearly, With these materials at 130 to 150° C. will have 75 the following examples are given. 2,512,582 5 6 Ecample I phates used. The total recovery of neutral or A mixture of butyl, acid phosphates was pre ganic phosphates was about 94% of theory; pared by the reaction of 3 mols of normal butanol Eacample III with 1 mol of phosphorus pentoxide. Three-hun dred sixty-three grams of this mixture were A mixture of amyl acid phosphates was pre neutralized by grinding in a mortar with about 3 pared by the reaction of 48 grams of phosphorus mols of solid potassium hydroxide: The resulting pentoxide with 88 grams of mixed amyl alcohols paste Was transferred to a reaction vessel-equipped derived from pentane and offered to the trade-as With a stirrer, thermometer and reflux condenser “pentasol.” The resulting amyl acid phosphates and refluxed with 630 grams of benzyl chloride 10 Were dissolved in 50 grams of triamyl phosphate for thirty hours. The reflux temperature re and neutralized with liquid (48%), potassium hy. mained at about 105-110° C. due to the Water droxide. One hundred milliliters of toluene was present in the mixture. Occasional additions of added and the mixture heated with removal of potassium hydroxide Were made to keep the re Water until a reflux temperature of about 120° C. action mixture neutral. At the end of the re 5 Was reached. Fifty grams of potassium carbon action period, the product was Washed with Water ate and 300 milliliters of benzyl chlorides were to remove precipitated potassium chloride. The added and the mixture heated to maintain. as re Organic layer Was distilled from 25 grams of so action temperature of 150° to 165°. C. for four dium carbonate under a pressure of about 5 mm. hours. The reaction mixture was. Washed with 20 water and the organic layer distilled from 20 of mercury. Fractions recovered were approxi grams of soda, ash. After removing low boiling mately as follows: materials the main product was distilled at 1509 Boiling Weight to 245 C. under 5 mm. of mercury, pressure and Fraction, Range, Collected, Probable Compositions. had a density at 25 C. of 1,064. After allowing oC. Grams 25 for complete recovery of triamyl phosphate sol vent, 170 grams: or 75% of the theoretical yield 1------to 150 150 benzyl chloride, benzyl alcohol, benzyl ether. of mixed-benzyl amyl phosphates was recovered. 2------i50-195 100 mainly dibutyl monobenzy phosphate. Eacample IV 3----- ... 195-220. 325. mily, buty dibenzyl phos pate. 30 Mixed octyl acid phosphates were prepared by 4------ar 220-250 50 tribenzyl phosphate and com the reaction of 3 mols of octyl alcohol (2-ethyl plex mixed-phosphates. hexanol) with 1 mol of phosphorus pentoxide. One hundred ninety seven grams; or one equiva The total weight of mixed alkyl benzyl phos lent of these acid phosphates was mixed with 100 phates recovered was about 475 grams, which 35 grams of benzyl octyl phosphates and 125-milli represents a yield of 75 percent based on the liters of toluene and neutralized with liquid phosphorus pentoxide used. (48%) potassium hydroxide. Water was then re By following the procedures of this example, moved until a reflux temperature of 120° C. Was I have produced other mixed alkyl benzyl phos obtained. After adding 10 grams of sodium car. phates including amyl benzyl phosphates, octyl 40 bonate, 230 milliliters of benzyl chloride and 2 henzyl phosphates and others from the salts of milliliters of tributyl amine, heating was con the corresponding alkyl acid phosphates. In fact tinued to 155-160° C. for three hours. The crude the salts of these higher alkyl esters are more re product was Washed and distilled under reduced active than those of butyl acid, phosphoric acid, pressure to give 340 grams of product boiling at and the same yield can be obtained in a lesser 45 200-230° C. under 2 mm. of mercury pressure and period of time. Kindred proportions of mixed having a density at 25° C. of 1.042. After allow propyl benzyl phosphate can be obtained by the ing for complete, recovery of the benzyl octyl process of this example by somewhat extending phosphates used as solvent, an 84% yield of the the reaction period. m desired product was recovered. Eacample II 50 It Will be understood that the embodiments of Two hundred and eighty grams of butyl acid my invention described and illustrated herein are phosphates such as used in Example I Were dis only representative of the principles of my in Solved in 300 grams of tributyl phosphate and vention and the agents used therein. Various 100 milliliters of toluene and neutralized by add modifications in the illustrative embodiments of ing liquid (48%) potassium hydroxide until a 55 my invention can be made Without departing permanent pink color Was obtained With phenol from the scope or spirit of the invention, which phthalein. Water Was removed as an azeotrope is defined in the appended claims. With toluene until a reflux temperature of about I claim: 120° C. was reached. Five hundred grams of 1. A process for making mixed alkyl benzyl benzyl chloride and 50 grams of sodium carbonate 60 phosphates which comprises heating and react were then added and the mixture heated to main ing an alkali metal Salt of an acid alkyl ortho tain a reaction teriaperature of 150 to 160° C. for phosphate with benzyl chloride in the presence four hours. At the end of the reaction period of an organic liquid medium, including water in the product was recovered as before and distilled a minor proportion, to distill part of the Water under good vacuum. After the removal of low 65 and raise the temperature of the reaction mass boiling materials, about 300 grams of product to between about 120 to 180° C. and continuing boiling between 130 and 160° C. at 5 mm. of mer the reaction by refluxing at said temperature. cury pressure was collected. This fraction Con 2. A process for producing neutral mixed alkyl tained mainly tributyl phosphate and represented benzyl phosphates which comprises heating and a substantially complete recovery of solvent. The 70 reacting an alkali metal Salt of an alkyl acid receiver Was changed and distillation continued Orthophosphate with benzyl chloride in the pres to recover 416 grams of product boiling at 160 ence of an alkali and a trialkyl phosphate con to 240° C. under 5 mm. of mercury pressure and taining the same number of carbon atoms in its having a density at 25° C. of 1,070. This repre alkyl radical as contained in the alkyl radical sents a yield of 91% based on acid butyl phos 75 of said phOSphate, 2,512,582 7 8 3. A substantially neutral composition com ganic phosphates which comprises refluxing and prising a substantially equal mixture of dialkyl reacting an alkali metal salt of an alkyl acid benzyl phosphates and monoalkyl benzyl phos orthophosphate in an organic liquid medium hav phates wherein the alkyl radical contains 8 car ing a boiling point above about 120° C. With ben bon atoms. zyl chloride. 4. A process for producing mixed tertiary or 12. A process for producing mixed tertiary Or ganic phosphates which comprises heating and ganic phosphates which comprises mixing phOS reacting benzyl monohalide in a liquid medium phorus pentoxide with an aliphatic alcohol in with an alkali, salt of an alkyl acid orthophOS molar ratios of about 1 to 3 to form a mix phate wherein the salt-forming group is selected O ture of alkyl acid orthophosphates, neutralizing from the group consisting of alkali metals and said mixture with an alkali to form an alkali Salt ammonia. 5. of an alkyl acid Orthophosphate wherein the Salt 5. A process for producing mixed tertiary or forming group is selected from the group Con ganic phosphates which comprises heating and Sisting of alkali metals and ammonia, and heat reacting a benzyl monohalide in an Organic liq 5 ing and reacting the neutralized mixture in an uid medium with an alkali metal salt of an alkyl alkaline Organic medium with an excess of benzyl acid Orthophosphate. monohalide. 6. A process for producing mixed tertiary or. EDWIN P. PLUEDDEMANN. ganic phosphates which comprises heating and reacting a benzyl monohalide in an Organic liquid 20 REFERENCES CTED medium maintained on the alkaline side of neu The following references are of record in the trality. With an alkali Salt of an alkyl acid Ortho file of this patent: phosphate. Wherein the salt-forming group is Se lected from the group consisting of alkali metals UNITED STATES PATENTS and ammonia. . . 25 Number Name Date 7. A process for producing mixed tertiary or 1844,408 Nicolai ------Feb. 9, 1932 ganic phosphates which comprises heating and 982,903 Clennensen ------Dec. 4, 1934 reacting an alkali metal salt of an alkyl acid 2,005,619 Graves. ------June 18, 1935 Orthophosphate in an organic liquid medium. With 2,008,478 Wanderbilt et al. ---- July 6, 1935 benzyl chloride at refluxing temperatures between : 2,241,244 Conary et al. ------May 6, 1941 about 120 and 180° C. - 2,266,514 Romieux et al.------Dec. 16, 1941 8. A process for producing mixed tertiary or 2,293,445 Nelson. (I)------Aug. 18, 1942 ganic phosphates which comprises heating and 2,354,536 Nelson (II) ------July 25, 1944 reacting an alkali metal salt of an alkyl acid 2,373,670 Engelke ------Apr. 17, 1945 orthophosphate in an organic liquid medium in 2,380,400 Browning ------July 31, 1945 the presence of an excess of alkali carbonate sus FOREIGN PATENTS pended in said liquid medium. With benzyl chlo ride by refluxing at temperatures between about Number Country Date 120 and 180°. C. 328,963 Great Britain ------Apr. 30, 1930 9. A process for producing mixed tertiary or 40 433,927 Great Britain ------Aug. 22, 1935 ganic phosphates which comprises heating and 145,985 Switzerland ------June i, 1931 reacting an alkali metal salt of an alkyl acid 566,514 Germany ------Dec. 17, 1932 Orthophosphate in an organic liquid medium with OTHER REFERENCES an excess of benzyl chloride under alkaline con ditions. 45 Zervas, “Naturwissenschaften," vol. 27, (1939), i0. A process for producing mixed tertiary or page 317. ganic phosphates which comprises heating and Atherton et al., “Jour. Chem. Soc. (London)' reacting a benzyl monohalide in an organic liq vol. 1945, pages 382-385. luid medium with a potassium salt of an alkyl “Chemical Abstracts,' volume 39, 4596-7 (Oct. acid orthophosphate wherein the alkyl radical 50 20, 1945), Abstracting Article by Atherton et al. contains at least 3 carbon atoms. in J. Chem. Soc. 1945, 382-5. 11. A process for producing mixed tertiary or