Patented Nov. 11, 1941 2262,431 UNITED STATES PATENT office 2262,431 - PROCESs of PREPARING EIGHocCULAR WEGB FA ACD COROES AndersonRobert J. W. Wander Ralston, Wall, Rales Chicago, R. McCorkle, assignors and to Armour and Company, Chicago, a corpora tionNoDrawing. of inos Application october 24, 1939, Serial Ne SOO84 6 claims (CLquently, 20-40s) separates completely from the fatty acid This invention relates to processes of preparing chloride but the fatty acid chloride will contain high molecular weight fatty acid chlorides and it unreacted phosphorus trichloride or pentachlo comprises processes wherein saturated or unsatu ride as the case maybe. rated fatty acids having six or more carbon atoms herefore, the problem in this art has been are reacted with an excess of a phosphorus halide that of purifying the fatty acid chloride. On a and the reaction product consisting of fatty acid small scale in the laboratory it is possible to re chloride and excess phosphorus halide, is treated move unreacted phosphorus trichloride by vac with water for the removal of the excess phos uum distillation. But on a large works scale vac phorus halide as an acid of phosphorus. uum distillation is unsatisfactory. In the first The high molecular-fatty acid chlorides, such O place, phosphorus halides are highly corrosive. as lauroyl chloride, stearoyl and the like are ma So are the fatty acid chlorides, and this requires terials of increasing importance for the synthesis distillation apparatus made from special, expen of new chemical compounds. For example, these sive metal alloys. In the second place, the fatty acid chlorides are useful in the preparation amount of unreacted phosphorus halide in the of ketonic compounds, esters and other sub 5 fatty acid chloride is rather slight so that large stances containing alkyl radicals of relatively quantities of fatty, acid chloride must be sub high molecular weight. In recent years much jected to distillation in order to remove very attention has been directed to the preparation of small quantities of phosphorus halide impurity. organic compounds containing alkyl or alkylene It is, of course, highly undesirable that the radicals having six or more carbon atoms. One 20 fatty acid chloride contain phosphorus halideim of the most convenient ways of making such com purities because these substances contaminate pounds is by using fatty acid chlorides as the chemical compounds prepared from the fatty source of the high molecular weight alkyl radical. acid chlorides. Since a major use for the fatty Such fatty acid chlorides are customarily pre acid chlorides is in the esterification of alcohols, pared by reacting the corresponding fatty acid especially polyhydroxy alcohols, fatty acid chlo with thionyl chloride, or a chloride of phosphorus, rides entirely free of phosphorus halides must such as phosphorus trichloride and phosphorus be used. Otherwise, a part of the alcohol reacts pentachloride. The present invention deals with with the phosphorus halide to give chlorinated improvements in that process wherein phos 30 products which contaminate the final ester. phorus chlorides, or phosphorus halides in gen In our search for a method by which crude eral, are used as the reagent for converting a fatty acid chlorides could be freed of unreacted higher fatty acid to its corresponding acid chlo phosphorus halides We have made the surprising ride. When a fatty acid, such as stearic acid, is re discovery that the halide can be hydrolyzed with acted with phosphorus trichloride an excess of 35 water or other hydrolyzing agent, such as methyl phosphorus trichloride is always present to insure or ethyl alcohol, without the water reacting with complete conversion of the fatty acid. Thus, for the higher fatty acid chloride. Normally it example, one molecular weight of phosphorus tri would be expected that the fatty acid chloride chloride will, in theory, convert three molecular Would also hydrolyze in the presence of the water Weights of a fatty acid to the corresponding fatty 40 to give free fatty acid. On the contrary, how acid chloride. Phosphorous acid is a by-product ever, we have discovered that the phosphorus of this reaction. When phosphorus pentachlo halides can be completely converted to the corre ride is used the reaction is similar to that when sponding acid of phosphorus by water without PCls is used excepting that phosphorus oxychlo effecting any substantial hydrolysis of the high ride is formed rather than phosphorous acids. 45 molecular weight fatty acid chloride present. But, as stated, it is essential that an excess of the After the hydrolysis is completed we then have a phosphorus halide be present. In consequence reaction mixture consisting of a layer of substan of this, the fatty acid chloride is always con tially pure fatty acid chloride and a layer of taminated with unreacted phosphorus halide. so phosphoric or phosphorous acid which can be The phosphorous acid, or phosphorus oxychlo readily separated from the fatty acid chloride ride obtained as one of the reaction products is by stratification. insoluble in the fatty acid chloride and thus forms In broad aspects then, our invention consists as a layer from which it can be removed from in treating crude fatty acid chloride mixtures thephorous reaction acid mixture or phosphorus by decantation. oxychloride, The conse- phos 65 containing unreacted phosphorus halides with 2 2,262,431 water or other hydrolyzing agent to convert the as described under Example 1, 75 parts by weight phosphorus halide to its corresponding acid. of water being used for the purpose of hydrolyz The present invention is applicable to the puri ing unreacted phosphorus trichloride in the lin fication of any fatty acid chloride having at least olenoyl chloride layer. six carbon atoms. These acid chlorides can be 5 Instead of using water as a hydrolyzing agent saturated or unsaturated. The present inven we can, of course, use the lower aliphatic alco tion is also applicable to fatty acid chlorides con hols, such as methyl or ethyl alcohol. But for taining either phosphorus trichloride or phos the purpose of economy we prefer to use water. phorus pentachloride as the phosphorus halide. Our process, as stated, is applicable to the Since the fatty acid chlorides are of chief inter O purification of all crude fatty acid chlorides hav est in the arts we shall describe our invention ing six or more carbon atoms and containing more particularly with reference thereto. But phosphorus halides. For example, such acid other fatty acid halides can be freed from the chlorides are caproyl, capryl, oleoyl, linoleoyl, as phosphorus halide therein in exactly the same well as those more specifically described above. manner. In no case need the reaction mixture be heated We shall now give examples showing how our to facilitate reaction between the fatty acid and invention may be practised. the phosphorus halide, and we need not apply Eacdimple 1 heat in the hydrolyzing step. Having thus described our invention, what we 3000 parts by weight of lauric acid are reacted 20 claim is: with 800 parts by weight of phosphorus trichlo 1. In the preparation of fatty acid chlorides ride. This is more than enough phosphorus tri having at least six carbon atoms by reacting the chloride as required by theory. The reaction corresponding fatty acid with a phosphorus hal mixture is allowed to stand until there is a clear separation of an upper layer consisting of ide used in excess, the method of removing un lauroyl chloride containing excess phosphorus reacted phosphorus halide from the fatty acid trichloride and a lower layer of phosphorous acid. chloride thus prepared which comprises hydro The lower layer is removed by drawing off from lyzing the unreacted phosphorus halide to its the upper layer and the upper layer than washed corresponding acid and then separating the acid with water. In this example, 162 parts by weight from the thus purified fatty acid chloride. of water are slowly added to the lauroyl chloride 30 2. In the process of preparing fatty acid chlo layer with constant stirring, the mixture is then rides containing at least six carbon atoms by allowed to settle whereby a lower phosphorous reacting the corresponding fatty acid with phos acid layer is formed. This lower phosphorous phorus trichloride used in excess, the method of acid layer is then removed leaving the lauroyl removing unreacted phosphorus trichloride from chloride substantially pure and free of phos the fatty acid chloride thus obtained which com phorus compounds. prises admixing water with the fatty acid chlo ride to convert the phosphorus trichloride to Eacample 2 phosphorous acid, and then separating the phos 2840 parts by weight of stearic acid are ad phorous acid from the fatty acid chloride. mixed with 504 parts by weight of phosphorus 40 3. The process as in claim 2 wherein the fatty, trichloride, together with about 1000 parts by acid contains eighteen carbon atoms. Weight of carbon tetrachloride. The carbon 4. The process of preparing acid chlorides of tetrachloride acts as a mutual solvent for the fatty acids containing at least six carbon atoms reaction mixture. No heat need be applied to which comprises reacting the fatty acid with an facilitate conversion of the stearic acid to stearoyl excess of a phosphorus chloride, Separating a chloride. The reaction mixture is then allowed crude fatty acid chloride containing unreacted to settle and the lower layer of phosphorous acid phosphorus chloride from the reaction mixture, separated off. The upper layer consisting of hydrolyzing the unreacted phosphorus chloride, Stearoyl chloride dissolved in carbon tetrachloride and separating the fatty acid chloride from the is then reacted with 75 parts by weight of water 50 reaction products. with constant stirring. The phosphorus tri 5. The process of preparing acid chlorides of chloride in the upper layer is thus converted to aliphatic acids containing at least six carbon phosphorous acid which separates as a lower layer atoms which comprises reacting a fatty acid with and can be readily removed. phosphorus trichloride, the amount thereof being 55 in excess of that required by theory, to give a re The upper layer of stearoyl chloride dissolved action mixture consisting of fatty acid chloride in carbon tetrachloride can be used directly for containing unreacted phosphorus trichloride and the preparation of aryl-alkyl ketones by a Friedel a stratified layer of phosphorous acid, separating Crafts reaction. The resulting Friedel-Crafts re the phosphorous acid from the fatty acid chlo action mixture forms no emulsion on hydrolysis CO ride, then adding water to the fatty acid chloride whereas if the fatty acid chloride were used di to convert phosphorus trichloride therein to rectly in a Friedel-Crafts reaction without first phosphorous acid, and finally separating the thus removing excess phosphorus halide emulsions formed phosphorous acid from the purified fatty Would tend, to form. acid chloride. Eacample 3 65 6. The process as in claim 5 wherein the fatty acid contains eighteen carbon atoms. 2800 parts by weight of linolenic acid are re ANDERSON W. RASTON. acted with 504 parts by weight of phosphorus MILES R. McCORKLE. trichloride. The reaction mixture is then treated ROBERT. J. WANDER WAL.