Ether carboxylates Applications

Also attributable to the polyglycol ether group between the fatty chain and the carboxylic group, the ether carboxylates have very mild dermatological properties, so that they have applications in mild cosmetics and household products [10,57,61,62,64,67-72]. 

From experience in metalworking applications it is known that ether carboxylates may improve the existing corrosion protection of formulations [66]. From pKj studies described by Aalbers [49], an internal neutralization of the ether carboxylate micelles can be concluded resulting in less anionic character than, for example, alkyl sulfates therefore also combination with quats are possible without any problem. 

The ether carboxylic acids are weakly dissociated [49], exhibiting nonionic behavior at low pH and anionic behavior at high pH. Due to this dual nonionic and anionic character a good emulsification effect can be achieved [66]. For many applications a high carboxymethylation of 80-90% is preferred [64] to obtain the wanted properties. 

All of the aspects and applications described in papers can be traced back to the patent literature [73]. The special or synergistic effect of ether carboxylates in combination with other surfactants is very often the basis, like combinations with alkyl ether sulfates or alkyl sulfates, for shampoos, foambaths, showerbaths, and liquid soaps [9,70,81-85], and the same for amidether carboxylates [71]. 

A special application of the ether carboxylic acid in metalworking has been described by Schuster [46] a boric acid ester has been produced by condensation of boric acid, alkanolamine, and alkyl ether carboxylic acid, eventually combined with a fatty acid. This condensation product gives less Ca soap precipitation, good anticorrosion effect, better removability of residues, and cleaner apparatus than the condensation product using only fatty acid. 

Subsequent studies and applications with ether carboxylates have been published [73]. Phase inversion temperature measurements, which can be used to select surfactants for enhanced oil recovery, showed good results when the phase inversion temperature of the system was just below the reservoir temperature [184]. 

One of the reasons that ether carboxylates are used in cosmetic products and some household detergents is their good dermatological behavior, as can be seen from several references in Sections IV.A and IV.B. Also their nontoxic and positive ecological properties have contributed to their increased use in these applications. 

Several other anionic surfactants are commercially available, such as sulfosuccinates, isethionates, and taurates, and these are sometimes used for special applications. The carboxylates and sulfates are sometimes modified by the incorporation of a few moles of ethylene oxide (referred to as ether carboxylates and ether sulfates, respectively). 

Ether carboxylates are a very versatile class of surfactants, used in diverse applications from mild personal care formulations to lubricants and cutting fluids. They are interrupted soaps, with the addition of a number of ethylene oxide groups between the alkyl chain and the carboxylate group. The additional solubility imparted by the EO groups gives much greater resistance to hardness and reduced irritancy compared to soap. 

Jackson, S.W. et al. (1996) Ether carboxylic acids and their salts, advances in technology and applications. Proceedings 4th World Surfactants Congress. 

The application of modern surface analysis techniques, such as XPS, to the analysis of modified polymer surfaces, has demonstrated that in most of the above processes the polymer is oxidized. Many functional groups such as hydroxyl, carbonyl, ether, carboxyl, ester, peroxide, epoxide, etc., have been detected by direct XPS analysis or after derivatization of functional groups. The interaction between evaporated metal films and several of such functional groups has been clearly demonstrated (3). 

Applications. Ether carboxylates are used as general emulsifiers and emulsion stabilizers. In households, they are used in acidic toilet bowl cleaners. For personal care, they impart mildness, creamy foaming, good skin feel, and hair conditioning benefits. Therefore, they are especially suitable in shampoos in combination with alcohol ether sulfates and possibly with cationics. 

For preparative purposes the Gattermann reaction is much more useful. It was first usedS5 to prepare ethyl 2-formyl-3,5-dimethyl- and ethyl 3-formyl-2,5-dimethyl-pyrrole-4-carboxylate, by means of hydrogen cyanide and hydrogen chloride in ether. Later applications sometimes involved minor changes such as the use of chloroform as solvent, or of Adams modification of the reaction . Formylation generally occurs at an a-position, but if none is open there is usually no difficulty in jS-substitution. Pyrrole-2-aldehyde cannot be made this way, for it reacts further to form dyestuffs, but several 1-alkylpyrroles have been satisfactorily formylated . The initial... 

Me3SiCH2CH=CH2i TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thiophenol except when CF3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-/-butyldi-methylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. 

The cationic pathway allows the conversion of carboxylic acids into ethers, acetals or amides. From a-aminoacids versatile chiral building blocks are accessible. The eliminative decarboxylation of vicinal diacids or P-silyl carboxylic acids, combined with cycloaddition reactions, allows the efficient construction of cyclobutenes or cyclohexadienes. The induction of cationic rearrangements or fragmentations is a potent way to specifically substituted cyclopentanoids and ring extensions by one-or four carbons. In view of these favorable qualities of Kolbe electrolysis, numerous useful applications of this old reaction can be expected in the future. 

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