Carboxy amphoterics

Carboxy amphoteric surfactants based on fatty alkyl imidazolines (imidazolinium surfactants) make up a large part of the amphoteric surfactants. Materials of this surfactant class are based on the imidazolines obtained by the condensation of fatty acids or their esters with aminoethyl ethanol amine. 

FIGURE 12.4 Carboxy amphoterics (alkylamino carboxylic acids). (From Rieger, M.M., Cosmet. Toil. 99, 61-67, 1984.)... 

Since peptides are amphoteric, Zt and Zc are expected to show nonlinear dependencies on pH. Similar behavior has been observed for various synthetic peptides separated on both strong anion and strong cation HP-IEX sorbents. As a consequence, the minima in the In /t iex i versus pH plots at a defined concentration of displacing salt will not usually occur at the predicted p/ value of the peptide, but rather at another pH value. Implementation of an optimized HP-IEX separation of peptides thus requires that the sequence microlocality and extent of ionization of the surface-accessible amino acid side chains, or the N- and C-terminal amino and carboxy groups, respectively, are taken into account. 

An L-B film is formed by the dispersion of amphoteric molecules at an air-water surface (Figure 8.20). These molecules have a polar group at one end, something like a carboxy substituent (in this respect they resemble the surfactant molecules which make micelles), and a long non-polar aliphatic chain. The polar group stays in the polar water phase, and the aliphatic chain stays in the non-polar air environment. The L-B film at the water surface is then made by the controlled compression of these molecules by means of a floating barrier. The molecules then line up to form a mono-molecular layer on the water surface. 

The other major class of fatty imidazoline derived amphoteric surfactants is the amphopropionates. Again, the ampho portion of the name indicates that they are derived from imidazolines but, rather than being alkylated with sodium chloroacetate, they are carboxy-lated with an acrylate via the Michael reaction. A primary or secondary amine is added across the double bond of the acrylate to yield the beta-alanine derivative. 

Together with pteriatoxins, pinnatoxins are the only cyclic imines that have a free carboxylic group at the cyclohexenyl side chain, whereas all other cyclic imino toxins form lactones. It is therefore very likely that pinnatoxins are not directly produced by microalgae, but rather that they are shellfish metabolites of related phycotoxins. Further evidence for this hypothesis can be seen from the fact that pinnatoxins occur with different side chains lengths, which may represent different stages of degradation of the parent compounds. Pinnatoxins are amphoteric due to their free carboxy group and the imino function, and they are soluble in ethanol and ethyl acetate at neutral pH. 

O and N carboxy methyl CS Reductive alkylation Direct alkylation Formation of an amphoteric polymer which extends the range of pH, enhancing CS solubility in different solvents Modified drug delivery pH responsive drug delivery DNA delivery Targeted drug delivery Permeation enhancer Cosmetics... 

Column 2 strongly basic anion exchanger hydroxide. Retains carboxy-lates and WW and SW amphoterics. Elute with hydrochloric acid. Car boxy lates and amphoterics are eluted rapidly. Response of phosphate esters is uncertain, but if they were not retained by column 1 they would be retained by column 2 and also eluted rapidly. Quaternary salts are converted to the hydroxide, weakly basic cationics (amines, amine oxides) to the free base and betaines to the zwitterionic form. All of these pass through. 

Kondo, M. Takano, S. Analysis of carboxy betaine amphoteric surfactants. Jpn. Kokai Tokkyo Koho JP 62006166,1987. 

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