in which the Rs have their usual meaning.The sulfosuccinimdes may be of two varieties, one analogous to the previously mentioned succinic acid derivatives, where the sulfonate group is added across the double bond of maleic acid and subsequently reacted to produce the cyclic imide. The second variety requires a different synthetic approach, since the locations of their hydrophilic and hydrophobic groups are reversed from those of the succinic acid derivatives. In this case, the starting material is a 2-alkyl, alkenyl, or similar succinic anhydride, which is reacted with the appropriate sulfoalkylamine to produce the amide acid, followed by dehydration to the imide. Similar reaction schemes can be used to prepare di- and higher polyesters and amides of malonic acid, itaconic acid, and other polycarboxylic acids.Unlike the sulfosuccinic acid derivatives, sulfopolyesters and amides, and imides of the phthalic acids and other sulfonated aromatic carboxylic acids can be prepared by a process such as the direct esterification or amidation of the corresponding acid.Various potential surfactant structures can be prepared from the other polycar- boxylic acids available to the synthetic chemist. Their properties as surfactants have received a great deal of attention because surface activity and solubility in water and organic liquids can be varied almost continuously by the proper choice of the esterifying alcohol. As mentioned earlier, the use of shorter-chain alcohols (
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