New Resins of the Phenolphthalein Series D. ZELINSKY ASD B. W. ~ I A K S O R O W Laboraiory of Organic Chemistry, 1st Unicersity, lMoscow, U. S.S. R. _U.
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HE probl(m of this researrh was to find new resins from phthalic anhydride and from phenol. As the first object for research, phenolphthalein was chosen, iince it is the simplest and most accessible condensation product of those two substances. C p to the present, it has been known that phenolphthalein, when heated above its melting point (250" to 280' C.), yields a dark brown resin, qoluble in alkalies, with a red coloration characteristic of the sodium salt of phenolphthalein. This solubility may be explained in two ways: either the conversion into a resin does not proceed fully; or the resin hydrolyzes under the influence of alkalies with the formation of the initial product. Because of its property of becoming colored under the influence of alkalies, its insufficient chemical resistance, and the dark color of its film, phenolphthalein, fused as a resin, has found no practical application. Kienle ( 3 ) tried t o condense phenolphthalein with glycerol and formaldehyde; the product with glycerol is half liquid and cannot be regarded as a resin. The condensation product with formaldehyde (although like Bakelite in its properties) has no technical and, more important, no economic advantage over Bakelite.
being vigorously shaken; phenolphthalein acetate was obtained by boiling phenolphthalein with acetic anhydride; the butyrate, benzoate, phthalate, salicylate, benzene sulfate, toluene wlfate, stearate, and palmitate, by heating the dry phenolphthalein sodium salt with an excess of the corresponding arylchloride. The purification of the esters was achieved by first pahsing steam through the products of the reaction, then shaking the product with dilute alkali (1 per cent solution), with water, and finally drying a t a temperature near 100" c. From the above-mentioned series of ethers and esters, tlie phenolphthalein toluylates are noteworthy because of their exceptional properties, including complete stability. While phenolphthalein benzoate (nearest the toluylate in chemical character) is a substance with two clearly expressed formsone being resin-like after fusion, and the other crystalline after recrystallization-the phenolphthalein toluylates are real resins, and t o modify them or to isolate a crystalline part by the usual methods was found to be impossible. Phenolphthalein benzylate after fusion remains a long time without change, but if it is dissolved in hot acetone or benzene, and then cooled, white crystals are precipitated, which may be collected and purified. If a dense solution of phenolphthalein benzylate (resin) is made in acetone, benzene, or benzene with alcohol, etc., with or without a plasticizer or oil, this solution, when poured into a glass or on a metal surface, forms a lacquer film which in a short time becomes turbid, owing to crystallization. Phenolphthalein toluylate behaves quite differently. Lacquer films of the latter resin made with alcohol-benzene, drying oil, etc., do not become turbid and remain transparent and brilliant.
ESTERSAND ETHERb The structure of phenolphthalein ethers and esters is as follows: STUDY O F PHESOLPHTHALEIN
CsHa00C12t.
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C-CHOOCRn
PHYSICAL PROPERTIES OF PHENOLPHTHALEIN TOLIJYLATES
These derivatives have very unusual properties; the esters, with the exception of a few which will be referred to later, show all the properties of the so-called pseudoresins, described by Eibner ( 1 ) and others. In a freshly fused condition, they are resin-like, transparent, lightly colored substances, which after a certain length of time become partly or wholly cryqtalline and therefore strongly resemble the natural resin, elemi, or the esters of abietic acid. While not going into the possible theoretical explanation of the conversion of resins into the crystalline state, it is neceqsary only to mention that the rate of conversion for different esters is different,. I t is, for instance, very slow for phenolphthalein benzoate, being evidenced only by a ;light turbidity of the resin surface a fen- months after its preparation; and it is very rapid for phenolphthalein acetate or butyrate. Complete turbidity of the whole mass occurs a few days after its preparation. In general it was possible to establish that the rate of conversion is in direct ratio to the molecular weight of the ether or ester radical, and is more rapid for esters than for ethers. In order to check this regularity, a series of esters and ethers were prepared: phenolphthalein acetate, butyrate, benzoate, phthalate, salicylate, benzene sulfate, toluene sulfate, stearate, palmitate, methylate, ethylate, benzylate, toluylate, glycolate, etc. The methods employed were the usual ones for obtaining phenol esters. Phenolphthalein methylate and ethylate were obtained by the action on phenolphthalein, in alkaline solution, of an excess of dimethyl and diethylsulfate, the mixture
Phenolphthalein toluylate from m-toluyl chloride melts, according to the method of Ubbelode, a t 8743°C. (depending upon the degree of purification) ; that from o-toluyl chloride melts a t 70-8Eio C. The saponification value of the m-toluylate, after boiling 1 hour with an alcohol solution of potassium hydroxide, is 70-88; its acid value is about 2. Toluylates, after evaporation of the solvent, form almost colorless films; these are brilliant, solid, waterproof and, still more important, have exceptional resistance to solutions of alkalies and acids. Thus it may be rightly said that the non-crystallizing ethers of phenolphthalein represent a new and, a t the same time, a very fine type of synthetic resin. The authors gave this resin the name of "alkalite," because of its high resistance t o alkalies. Its industrial value is evident if alkalite is compared, in respect to its resistance to alkalies, with alreadyhnown natural and synthetic resins, paraffing, asphalts, etc. In Table I are shown the results of tests on various materials. The resistance to alkalies was determined by soaking a piece of the sample, having a measured surface, in a 10 per cent solution of caustic soda (5 cc. of alkali per square centimeter of surface) with a subsequent titration of the alkali with a 0.1 N solution of potassium permanganate after a definite length of time. If before the first titration the sample went to pieces, the titration was not effected. The quantity of potassium permanganate per square centimeter was taken as the measure of solubility of the sample in alkali. This method with potassium permanganate has been-tested and 63
