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Patented Oct. 23, 1951 2,572,806 UNITED STATES PATENT OFFICE 2,572,806 MANUEFACTURE OF TETRAETHY, PYROPHOSPAATE John Sterling Harris, Richmond Heights, Mo., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application May 1, 1948, Serial No. 24,683 2 Claims, (C. 260-461) 2 This invention relates to compositions con enty known to the art. A still further object of taining increased amounts of tetraethyl pyro this invention is to provide biological toxicant phosphate, and more. particularly to a process compositions containing increased amounts of for the manufacture of tetraethyl pyrophosphate. tetraethyl pyrophosphate which poSSeSS over Compositions containing tetraethyl pyrophos 5. S00% greater biological activity for the combat phate are widely used as agricultural economic ing and control of pests such as aphids and mites poisons, particularly against many insects such than do the compositions containing tetraethyl as aphids and against many acarina such as the pyrophosphate which are presently known to red Spider mites, however, such compositions may the art. be used generally against the lower forms of life O In the practice of this invention, the mixtures which, in the past, have been combatted by the of reaction products from the processes of this use of nicotine or nicotine salts. Furthermore, invention contain substantially 40%, that is tetraethyl pyrophosphate has been found useful 38-45%, of tetraethyl pyrophosphate as con in the preparation of insectivoricide and rodenti trasted with the processes of the prior art which cide compositions. 5 yielded mixtures of the reaction productS con While the art has disclosed several methods for taining only 10-15% of the tetraethyl pyrophoS the preparation of tetraethyl pyrophosphate, phate. For uses where substantially pure tetra most of these methods are of interest only from ethyl pyrophosphate is required, the tetraethyl a purely academic and theoretical viewpoint. pyrophosphate may be separated from the mix Prior to this...invention, there has not been a prac 20 tures of reaction productS by high Vacuuin frac tical commercial process for the production of tional distillation (below one millimeter of ner tetraethyl pyrophosphate in good yields from cury) or by one of the solvent extraction meth readily available raw materials. It has become ods as are described and claimed in the United known to the art that when phosphorus oxy States application Serial No. 24,918 filed May 3, chloride is reacted with the neutral triethyl ester 1948, now. United States Patent No. 2,523,613 of of Ortho-phosphoric acid in a mol ratio of about Dvornikoff or patent application Serial No. 24,672, 1:3 at temperatures of about 130° C. to 150° C., filed May 1, 1948, now United States Patent No. While the resulting mixture of reaction products 2,523,243 of Willis. It is evident that when Sub contains predominantly hexaethyl tetraphos stantially pure tetraethyl pyrophosphate is re phate, there is also present in the mixtures of re quired, that the recovery of the tetraethyl pyro action products about 10-12%, and seldom more phosphate from the reaction mixture of this in than 15%, of tetraethyl pyrophosphate. It is vention containing 38-45% of tetraethyl pyro extremely difficult and tedious to concentrate or phosphate is much more efficient and is to be pre Separate the tetraethyl pyrophosphate from the ferred over the recovery of the tetraethyl pyro mixture of reaction products as almost all of these 35 phosphate from the reaction mixtures of the prior reaction products are subject. to hydrolysis when art which contain only 10-15% of tetraethyl pyro in contact with water and when separation is at phosphate. However, the reaction mixtures tempted by fractional distillation, the fractiona themselves from the proceSSes of this invention tion must be carried Out under a vacuum of a may be advantageously and Satisfactorily used fraction of a millimeter of mercury, as decompo 40 as biological toxicants, likewise these reaction Sition of the tetraethyl pyrophosphate takes place mixtures as such may be used to formulate bio at the temperatures required for distillation under logical toxicant compositions without first Sepa a lower vacuum and maintenance of such very rating the tetraethyl pyrophOSphate from the high, vacuums for distillation purposes. is ex reaction mixtures. The mixtures of reaction tremely expensive, and undesirable, in a commer 45 products from the processes of this invention cial process. are over 300% as biologically active against Such It is an object of this invention, therefore, to pests as aphids and mites as are the compositions provide a proceSS for the production of tetraethyl containing only 10-15% of tetraethyl pyrophoS pyrophosphate in Substantially increased yields phate which are presently known to the art. over the yields obtained by the processes, pres 50 I have discovered that tetraethyl pyrophos ently known to the art. A further object is to phate may be obtained in substantially 40% yields provide a process for the production of reaction by the reaction of hexaethyl tetrapolyphosphate Inixtures containing tetraethyl pyrophosphate in With triethyl phosphate in the mol ratio of Sub substantially increased concentrations over the stantially 1... mol of the hexaethyl tetrapolyphos concentrations obtained from the processes pres 55 phate to 2 mols of the triethyl phosphate. This 2,572,806 3 4. reaction may be carried out within the tempera slowly added, in a drop-wise manner and with ture range of 125° C. to 160° C. However, the stirring, to the triethyl phosphate. After all of optimum yields are obtained when the reaction the phosphorus oxychloride had been added to is carried out at a temperature of Substantially the triethyl phosphate, the temperature Was 145 C. maintained at 150° C. for an additional 2 hour While the highest yields of tetraethyl pyror to finish off the reaction. In addition to the phosphate are obtained when hexaethyl tetra hexaethyl tetraphosphate present, quantitative polyphosphate is reacted with triethyl phosphate chemical analysis of the reaction mixture in in the mol ratio of 1 mol of hexaethyl tetra dicated a 10.9% content of tetraethyl pyrophoS polyphosphate to Substantially 2 mols of triethyl O phate. phosphate, yields of substantially 40% tetraethyl Eacample IV pyrophosphate may be obtained when 1.5 to 3 The reaction mixture from Example III was mols of triethyl phosphate are reacted With 1 inol then heated to 135° C. and 121.4 g. (% mol) of hexaethyl tetrapolyphosphate. However, it is of triethyl phosphate was then added to this preferred to hold the nol ratio within the ratio 15 first reaction mixture, with stirring, and at a of 1 mol of hexaethyl tetrapolyphosphate to 1.9 rate so as to maintain a reaction temperature to 2.1 mols of triethyl phosphate. In carrying of about 135° C. After all of the triethyl phos out the process of this invention, the hexaethyi phate had been added, the temperature of the tetrapolyphosphate need not be separated from reaction mixture was increased to 145° C. and the mixtures of reaction products by which the 20 hexaethyltetrapolyphosphate was made. Rather, this temperature was maintained and the stirring the triethyl phosphate may be added to the reac continued for an additional two hours, yielding tion mixtures containing the hexaethyl tetra a second reaction mixture. Quantitative chem polyphosphate in the proper mol proportions and ical analysis of this second reaction mixture the reaction carried out under the described Con 25 indicated a 41.2% content of tetraethyl pyro ditions to obtain reaction mixtures containing phosphate. tetraethyl pyrophosphate in a Substantially 40% Eacample V yield. A portion of the mixture of reaction products The following examples are illustrative of the from Example III containing 41.2% tetraethyl method by which this invention may be prac 30 pyrophosphate was fractionally distilled under ticed, however, it is not intended that this inven a vacuum of 0.6 millimeter of mercury and the tion be limited solely to the processes as set forth substantially pure tetraethyl pyrophosphate re in the following examples: covered. Eacample I Eacample VI 506 g. (1 mol) of hexaethyl tetraphosphate 546.6 g. of triethyl phosphate Were placed in were slowly warmed to 135° C. in a glass re a glass reaction vessel equipped with reflux con action vessel equipped with a reflux condenser denser. The triethyl phosphate was warmed to and 364.4 g. (2 mols) of triethyl phosphate Were 130° C., at atmospheric pressure, and 1434 g. of gradually added, With stirring, to the Warned 40 phosphorus oxychloride (a mol ratio of 3:1) Were hexaethyl tetraphosphate at such a rate So as gradually added, with stirring, to the warmed to maintain a reaction temperature of about 135° triethyl phosphate at such a rate So as to main C. After all of the triethyl phosphate had been tain a reaction temperature of about 130° C. added to the hexaethyl tetraphosphate, the re which required about two hours. After all of the action mixture was then heated to about 145° C. phosphorus oxychloride had been added to the and thereafter maintained at 145° C. for an triethyl phosphate, the reaction mixture WaS additional two hours during which time the re then slowly heated to 145° C. Over a period of action maSS Was continuously stirred. Quantita one hour and thereafter maintained at 145” C. tive chemical analysis of the reaction mixture for an additional hour. Quantitative chemical indicated that the reaction mixture contained analysis of this reaction mixture indicated a 40.5% tetraethyl pyrophosphate, and biological 15.0% content of tetraethyl pyrophosphate. aSSay of the reaction mixture indicated that the Eacample VII biological activity of this reaction mixture was inore than 300% greater than the biological Thereafter, the reaction mixture from Example activity of compositions containing hexaethyl VI was warmed to 130° C.

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