324 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS stood that this material ethoxylates in an unusual manner. The process called etheni- fication is well known and is outlined in equation 1. The ethylene oxide is added both to the ester group and to the hydroxyl group. It is therefore possible to evaluate the relative amounts of ethylene oxide that adds to each functionality. In short, there is a group selectivity or preference for ethoxylation. This group selectivity can be classified as strong, intermediate, or weak, depending on the results obtained with the ethoxylation. Equation 1 (idealized) OH CH3-(CH2)5-CH-(CH2)lo-C(O)-O-CH2 OH CH3-(CH2) 5-CH-(CH2)•o -C(O)-O-CH OH I CH3-(CH2) 5-CH-(CH2)10-C(O)-O-CH2 // + n CH 2 O -- CH 2 (OCH2CH2)a-OH CH3-(CH2)5-CH-(CH2)lo-C(O) (OCH2CH2)x-O-CH 2 (OCH2CH2)b-OH I CH3-(CH2)5-CH-(CH2)lo-C(O) (OCH2CH2)Y-O-CH (OCH2CH2)c-OH I CH3-(CH2)5-CH-(CH2)10-C(O) (OCH2CH2)z-O-CH 2 n=a+b+c+x+y+z The material to be ethoxylated is introduced into a clean dry vessel with the desired catalyst, if any. When all the ethylene oxide has been added, the molar ration of ethylene oxide to fatty material is one to one. The contents are then heated to 150øC under agitation. Vacuum is applied to 20 mm for one hour, to remove any water. The vacuum is released, and ethylene oxide is applied under pressure. The contents are then ethoxylated at 150øC and 45 psig. After all the oxide has been added, the reaction mass is held for one hour at 150øC.

ETHOXYLATION OF HYDROXY ACIDS 325 Our analysis of the above reaction using one mole of ethylene oxide with one mole equivalent of hydrogenated castor oil, using 0.1% KOH as catalyst, gave the following results: Ester reaction 58% Hydroxyl group 29% Polyethylene glycol 13% 12-HYDROXYSTEARIC ACID ETHOXYLATION 12-hydroxystearic acid is prepared by the saponification and purification of hydroge- nated castor oil. Bullen (12) studied the ethoxylation of 12-hydroxystearic acid using base catalyst. His conclusions were that "it appears that the condensation product of ethylene oxide with 12-hydroxystearic acid is not affected by the type of catalyst used in its preparation and the polyethenoxy-12-hydroxystearate so obtained by using KOH, under base catalysis all the oxide was added to the carboxyl group" (6). Our base catalyzed ethoxylation of 12-hydroxystearic acid resulted in the confirmation of the Bullen results: Initial Final Rxn time Final Catalyst acid value acid value (hr) OH value % Diester 0.2 KOH 164.2 0.5 1.5 247.2 25.1 0.1 KOH 164.2 0.1 1.1 244.1 24.0 The ethoxylation of one mole of hydroxystearic acid with one mole of ethylene oxide using 0.1% KOH as a catalyst resulted in 99% of the ethylene oxide reacting at the carboxyl group, with essentially no reaction at the hydroxyl group and about 1% polyethylene glycol. The major surprise, based upon the observations of Bullen, was that the induction period normally anticipated with the ethoxylation of a fatty acid was totally absent. The rate of ethoxylation was almost identical to that of a fatty alcohol, and very dissimilar to that of a fatty acid. The distribution of products and the group selectivity were as anticipated by Bullen. As a control, one mole equivalent of stearic acid was ethoxylated with one mole equiv- alent of ethylene oxide: Initial Final Rxn time Final Catalyst acid value acid value (hr) OH value % Diester 0.2 KOH 172.2 4.06 1.25 137.3 19.9 These results matched well with the results of Wrigley (7). CATALYSTS Realizing that neither fatty alcohols nor fatty acids ethoxylate without a catalyst, we tried to ethoxylate 12-hydroxystearic acid without a catalyst. To our surprise, the material ethoxylated without an induction period. The rate was comparable to the rate of ethoxylation of the base-catalyzed fatty alcohol ethoxylation. The product types that resulted after the ethoxylation of one mole equivalent of 12-