GROUP SELECTIVITY OF ETHOXYLATION OF HYDROXY-ACIDS

A study of the ethoxylation of two hydroxy acids was undertaken to det ermine if there was any group selectivity of ethoxylation. The hydroxy acids chosen for study were 12-hydroxystearic and lactic acid. Standa rd ethoxylation reactions were carried out using one mole of ethylene oxide to one mole of each hydroxy acid. Unlike typical fatty acids or alcohols, 12-hydroxystearic acid and lactic acid both ethoxylate witho ut a catalyst. This could be explained by the presence of both a hydro xyl and carboxyl in the reaction solution or the presence of both grou ps in the same molecule. We suggest that this may be due to some type of complex forming between the oxide and the carboxyl and hydroxyl gro ups, since blends of stearic acid and stearyl alcohol fail to ethoxyla te without a catalyst. Despite the fact that carboxyl groups of the hy droxy acids studied ethoxylate almost exclusively under base catalyst, and predominately with no catalyst, the reaction rate does not show a n induction period, which would be expected for carboxyl group ethoxyl ation. The ethoxylation rates approximate those of primary alcohols un der base catalyst. Ethoxylation of both hydroxyl groups and carboxyl g roups has been practiced for many years in the preparation of many sur face-active agents. Fatty acid ethoxylates and fatty alcohol ethoxylat es are members of a wide range of ethoxylates that are excellent surfa ctants. Surfactants are surface-active agents that function as deterge nts, wetting agents, and emulsifiers. They are used as solubilizers, c oupling agents, fiber lubricants, antistats, leveling agents, and dyei ng assists (1). In addition, these materials are used in numerous pers onal care applications and are key raw materials in the preparation of other surfactants like fatty alcohol ether sulfates. Ethylene oxide r eacts in an extremely exothermic manner with compounds having a labile hydrogen. Fatty acids and fatty alcohols are two of many such compoun ds containing a labile hydrogen. Alkaline and acidic catalysts make th e reaction possible and accelerate it.