ETHOXYLATION OF HYDROXY ACIDS 327 to 12-hydroxystearic acid and (b) the group selectivity of the ethoxylation reaction of lactic acid differs considerably from the group selectivity of ethoxylation of 12- hydroxystearic acid. ETHOXYLATION RATES Table III outlines the amount of ethylene oxide added to various hydroxy-containing compounds. It shows that stearic acid, because of the anticipated induction period, ethoxylates significantly more slowly than the alcohols evaluated. Stearyl alcohol, castor oil, and 12-hydroxystearic acid all exhibit about the same rate of ethoxylation. No- nylphenol, which has a more acidic hydroxyl group than a primary or secondary alcohol, ethoxylates most rapidly. Table III shows the amount of ethylene oxide added to various hydrophobes using 0.1% KOH catalyst. Stearyl alcohol has added 4.2 moles of ethylene oxide in two hours, while nonylphenol has added 9.5 moles in the same time. CONCLUSIONS We have found that the ethoxylation of 12-hydroxystearic acid and lactic acid are unusual in several respects: 1. Unlike typical fatty acids or alcohols, 12-hydroxystearic acid and lactic acid both ethoxylate without a catalyst. This could be explained by the presence of both a hydroxyl and a carboxyl in the reaction solution or the presence of both groups in the same molecule. The attempt to ethoxylate a blend of fatty acid and fatty alcohol without a catalyst did not succeed. Consequently, it appears that the two groups need to be present in the same molecule. We suggest that some type of complex forms between the oxide and the carboxyl and hydroxyl groups. We would also predict that the location of the hydroxyl group relative to the carboxyl group is important, but we do not have the needed data to prove that at this time. 2. There is a high degree of group selectivity to the ethoxylation of 12-hydroxystearic acid and lactic acid. The carboxyl group ethoxylates almost exclusively under base catalyst. When no catalyst is used, 33% of the added oxide goes to the hydroxyl group and 67% to the carboxyl group when one mole of oxide is added to 12-hydroxystearic Table III Moles of Ethylene Oxide Added Versus Time at Reaction Conditions 0.1 KOH 12-hydroxy Time (hrs) Nonyl phenol Stearyl alcohol Castor oil stearic acid Stearic acid 0 0 0 0 0 0 1.0 4.9 1.1 1.4 1.0 0.5 1.5 7.5 2.5 3.3 2.2 0.6 2.0 9.5 4.2 6.1 4.3 0.8 2.5 11.1 7.0 8.2 6.8 3.0

328 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS acid. The carboxyl group of lactic acid ethoxylates almost exclusively when it is ethox- ylated with one mole of ethylene oxide without a catalyst. 3. Despite the fact that the carboxyl group of 12-hydroxystearic acid ethoxylates almost exclusively under base catalyst, and predominately with no catalyst, the reaction rate does not show an induction period, which would be expected for carboxyl group ethox- ylation. This difference in kinetics would suggest another mechanism for the reaction under both conditions. Ethoxylation of lactic acid likewise shows no induction period. 4. The ethoxylation of both 12-hydroxystearic acid and lactic acid, which predomi- nately occurs on the carboxyl group, follows reaction rates approximating that of pri- mary alcohols under base catalyst, despite the fact that the hydroxyl groups in both acids are secondary hydroxyl groups. 5. The following is the relative order of reaction of various hydrophobes with one mole of ethylene oxide arranged from the fastest to the slowest: Fastest ethoxylation nonyl phenol lactic acid stearyl alcohol = castor oil = 12-hydroxystearic acid stearic acid Slowest Ethoxylation ACKNOWLEDGMENT The authors gratefully acknowledge the assistance of Ethox Chemical in Greenville, S.C., for preparation of many of the ethoxylates studied. REFERENCES (1) A. J. O'Lenick and R. McCutchen, An overview of alkoxylated alcohols, Soap Cosmet. Chem. Spec., 64(1) (1988). (2) C. F. Stevens, Nonionic surfactants, JAOCS, 34 (1957). (3) U.S. Patent 4,360,698, issued Dec 1981. (4) U.S. Patent 4,456,697, issued June 1984. (5) U.S. Patent 4,568,774, issued February 1986. (6) U.S. Patent 4,593,142, issued June 1986. (7) A. N. Wrigley, F. D. Smith, and A. J. Stirton, Comparative detergents from animal fats, JAOCS, 34 (1957). (8) K. Nagse and K. Sakaguchi, Kogyo Kagaku Zassi, 64, 1035 (1961). (9) H. F. Drew and J. R. Schaffer, Ind. Eng. Chem. 50, 1253 (1958). (10) G. Tishbirek, Proceedings of the Third International Congress on Surface Activity, Cologne, 1, 126 (1960). (11) J. D. Malkemus andJ. D. Swan, J. Am. Oil Chem. Soc., 31, 71 (1954). (12) A. T. Bullen, J. N. Schumaker, G. E. Kapella, and J. V. Karabinos, Comparative detergency of several built polyethenoxy alkanoates, JAOCS, 31 (1954).