Amino acid surfactants representative structure

A schematic of routes for the synthesis of amino acid surfactants is shown in Fig. la representative structures are illustrated in Fig. lb. The Schotten-Baumann method is a typical and useful way to synthesize A -acylamino acid. 

FIG. 1 Continued, (b) Representative structures of amino acid surfactants. R Long chain alkyl radical Rh Amino acid s sidechain R Alkyl radical, etc. 

Structurally, amino acid-based surfactants may be depicted as shown nearby. The fundamental stmctures may be considered as (1) N-acylated amino acid, which is essentially an anionic surfactant, or modified as in (b), where the carboxylic group is converted to ester or amide, as seen in cationic surfactants. The structures in (c) and (d) represent those of amphoteric surfactants, in which both amino and carboxyl groups represent hydrophilic moieties. 

Many compounds containing a perfluorinated or hydrogenated hydrophobic chain and an amino acid as either polar head or junction modulus have been synthesized. Among the different structures that have been prepared, a variety of amino acids are encountered, but a-amino acids are the most common however, P-alanine or its derivatives play an important role, too. Moreover, molecules based on perfluoroalkyl-amino acids, prepared from different functionalized perfluoroalkyl starting compounds, have been synthesized. It should be stressed that the different types of surfactants based on amino acids encountered in this family of products may be classified as ionic, nonionic, or zwitter-ionic. In all the structures obtained, the concept of modularity is important, since the amino acid—with or without prior chemical transformation—represents either the polar head group or a pivot modulus linking one or more lipophilic chains to different polar heads. 

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