Patented Aug. 8, 1939 2,168,346 UNITED STATES PATENT OFFICE 2,168,346 PROCESS OF PRODUCING PHENOLPHTAEN Max Hubacher, Valley stream, N.Y., assignor to Ex Lax, Inc., a corporation of New York No Drawing. Application February 11, 1938, Seria No.190,030 - - - - 5 Claims. (CI. 260-337) The present invention relates to improvements give the beneficial effects, i. e., high yields of in processes of manufacturing phenolphthalein phenolphthalein in relatively short time. Mix and has as its objects simplicity and economy and tures containing 37% phthalylchloride and 63% a high grade of purity of the product. phthalic anhydride with phenol are equally well Fhenolphthalein can be prepared by Various Suited. - - methods, but only the one using a raw material The following examples will illustrate more phenol and phthalic anhydride is of commercial clearly my proceSS:- interest. The presence of a condensing agent is necessary to bring about the reaction of phenol Eacclimple No. O with phthalic anhydride to form the phenol A jacketed enamel kettle is charged with 188; O phthalein. Many substances have been proposed lbs, phenol and 140 lbs. phthalic anhydride. The as a condensing agent. Stannic chloride, already mass is heated to 35-40° C., the stirrer started used by the discoverer of phenolphthalein, A. W. and 80 lbs. anhydrous zinc.chlodie added. After Baeyer (A. 202, 69 (1880) ) is a good agent, but the mixture has become fairly Well liquefied, With 5 its price is prohibitive and methods of recovery out raising the temperature substantially above not economical. Concentrated Sulfuric acid 45° C., 10 lbs. of technical phthalylchloride is brings about the reaction between phenol and charged over a period of about 15 minutes. The phthalic anhydride, but the acid also reactS With temperature of the reaction mixture is then raised the phenol to form phenolsulfonic acid. A part Within about 45 minutes to 118-122 C. The of the phenol is thus withdrawn from reacting mass is kept stirring at this temperature for 16 20 with the phthalic anhydride; as a consequence, hours, the time being counted from the moment the yield of phenolphthalein is not very satis the temperature has reached 115. The Semi factory. Furthermore, when concentrated Sul solid reaction mass is dropped into a tank Con furic acid is used, varying amounts of tarry and taining hot water. After washing it repeatedly resinous and colored by-products are formed With hot Water to remove the ZincChloride as 25 25 along with the phenolphthalein and these unde well as the unreacted phenol and phthalic acid, sirable impurities make the Subsequent purifica it is dried. 266 lbs. crude phenolphthalein Was tion difficult. obtained. This crude product, after treating it in The present invention has for its object the the usual way with dilute caustic to remove the production of a crude phenolphthalein in the fluoran, had a yield of 244 lbs. phenolphthalein of 30 30 shortest time possible, having a maximum amount melting point 255.8-258.6° C. The yield is 76.7% of phenolphthalein and a minimum amount of of the theoretical. by-products. When phenol and phthalic anhydride are Eacample No. II heated in the presence of anhydrous commercial Under the same working conditions, 188 lbs. 35 35 zinc-chloride, then the condensation reaction pro phenol, 118 lbs. phthalic anhydride, 80 lbs. an ceeds slowly. After 40 hours at 115-120° C. the hydrous zinc.chloride and 41 lbs. technical yield of phenolphthalein was only about 58% phthalylchloride were heated for 15 hours at of the theoretical based on the phenol charged 113-117. C., 282 lbs. crude phenolphthalein was (Walter Herzog, Chemiker - Zeitung 51, 84 obtained and from this, after the removal of the 40 40 (1927)). It is also known that phenolphthalein fluoran, 270 lbs. phenolphthalein melting at is obtained by heating phenol and phthalyl 256.7°-259.7° C. Was obtained. The yield is 84.9% chloride in the presence of a condensing agent, of the theoretical. but the yield is reported as only 1.2% of the Eacample No. III 45 theoretical (Blicke, Smith and Powers, J. Am. 45 Ch. Soc. 54, 1471 (1932)). 188 lbs. phenol, 104 lbs. phthalic anhydride, 90 I have discovered that crude phenolphthalein lbs. anhydrous zinc.chloride and 61 lbs. technical containing a minimum amount of by-products phthalylchloride were heated for 6% hours at can be produced in relatively short time and in 125-127 C., 280 lbs. crude phenolphthalein was high yields by heating a mixture of phenol, obtained and after treatment with dilute caustic, 50 50 phthalic anhydride and phthalylchloride in the 254 lbs. phenolphthalein of melting point presence of anhydrous zinc.chloride. The 2546-257.0° C. The yield is 79.8% of the theo amount of phthalylchloride can be varied Within retical. wide limits. 5% of phthalylchloride based On The temperature of reaction is not limited to 55 the weight of phthalic anhydride was found to the range of 113-127 C. Equally good results 5 2 2,168,346 are obtained at somewhat lower and up to about temperature not exceeding 80, adding anhydrous 135° C. The method is not limited to the pro zinc.chloride to the liquefied mixture, and raising portions given in the above three practical ex and maintaining the temperature of the reaction amples. An excess of either one or more of the mass between 100 and 140. chemicals may be used, or the chemicals may be 4. A process of producing phenolphthalein, added in a different Order. characterized by mixing phthalic anhydride with Having described my invention, what I claim phenol, until a homogeneous Solution is obtained, and desire to Secure by Letters Patent is as adding phthalylchloride and anhydrous zinc follows: chloride to the mixture and agitating the mass O 1. A process of producing phenolphthalein by . at a temperature of from 100-140 until the con O condensing a mixture of phenol, phthalic anhy densation is completed. dride and phthalylchloride in the presence of an 5. A process of producing phenolphthalein hydrous zinc.chloride. which consists in mixing phenol in the proportion 2. A process of producing phenolphthalein of 188 pounds, phthalic anhydride in the propor 5 which consists in liquefying a mixture of phenol tion. Within a range of 104 to 140 pounds, anhy 5 and phthalic anhydride, adding anhydrous zinc drous zinc.chloride within a range of 80 to 100 chloride to the liquid, and then adding phthalyl pounds and phthalylchloride Within a range of 10 chloride at a temperature not exceeding 80°, to 61 pounds, the mixture being stirred and heated thereupon raising the temperature to 100°-140°,- to a temperature of 100-40 for a period be 20 and after the formation of the phenolphthalein, tween substantially 6% to 16 hours, removing the it) removing the unreacted phenol and phthalican Zincchloride, the unreated phenol and the unre hydride as well as the zinc.chloride. - acted phthalic anhydride to obtain crude phenol 3. A process of producing phenolphthalein phthalein. which consists in heating a mixture of phenol, 25 phthalic anhydride and phthalylchloride to a MAX HUBACHER. 25 .