ABSTRACT
Quaternary surfactants are simply characterized in that they bear a cationic charge in the molecule [1-5,6]. Typically, one or more long-chain hydrophobic hydrocarbon groups with a C-chain length between C6 and C22 are linked to a cationic group. Several cationic groups are known (Figure 20.1). But products based on phosphonium and sulfonium that can be used as phase-transfer catalysts [7] are less important. Products containing an ammonium group are the only signi cant ones within the group of cationic surfactants.
