Alkyl betaines

The solubihty characteristics of sodium acyl isethionates allow them to be used in synthetic detergent (syndet) bars. Complex blends of an isethionate and various soaps, free fatty acids, and small amounts of other surfactants reportedly are essentially nonirritant skin cleansers (66). As a rule, the more detersive surfactants, for example alkyl sulfates, a-olefin sulfonates, and alkylaryl sulfonates, are used in limited amounts in skin cleansers. Most skin cleansers are compounded to leave an emollient residue on the skin after rinsing with water. Free fatty acids, alkyl betaines, and some compatible cationic or quaternary compounds have been found to be especially useful. A mildly acidic environment on the skin helps control the growth of resident microbial species. Detergent-based skin cleansers can be formulated with abrasives to remove scaly or hard-to-remove materials from the skin. 

Alkylation, betaine, 63-64, 67 Alkynes, decamethylsilicocene reactions with, 24-25... 

A broad range of information pertaining to the toxicity of several classes of surfactants including anionic (linear alkylbenzene sulfonates (LAS), alkylether sulfates (AES), alkyl sulfates (AS), non-ionic (alkylphenol ethoxylates (APEO)), cationic (ditallow dimethyl ammonium chloride (DTDMAC)—a group of quaternary ammonium salts of distearyl ammonium chloride (DSDMAC)) and amphoteric surfactants (alkyl-betaines) is available. Several reviews of the scientific literature have been published [3-5,20]. 

R. A. Thompson, S. Allenmark, The Effect of Long-Chain Alkyl Betainates on the Ar-ylesterase-Like Activity of Bovine Scrum Albumin , llioorg. Chem. 1992, 20, 356-365. 

In contrast to this, there is little information available (11) on the thermodynamics of adsorption of alkyl betaines and no data on the thermodynamic parameters of adsorption or micellization for sulfobetaines. 

Three homologues in which n = 8 (CsBMT), 10 (CioBMT), and 12 (C12BMT) were synthesized by a procedure similar to that for the N-alkyl-betaines. Here, the N-methyl benzyl amine and sodium salt of 2-chloro-ethanesulfonic acid were refluxed in 95% methanol for two days. 

In Figure 1, the log of the cmc is shown as a function of the number of carbon atoms in the hydrocarbon chain, n, . It is clear that the nonionic surfactants (hexaethyleneglycol alkyl ethers) and the zwitterionic surfactants (N-alkyl betaines) exhibit linear relations with similar slopes of about -0.5... 

G(CH2) thus calculated is -705 cal/mol and -657 cal/mol for hexaethyleneglycol alkyl ethers and N-alkyl betaines, respectively, as shown in Table 1. 

These are surfactants containing both cationic and anionic groups. The most common amphoterics are the A-alkyl betaines, which are derivatives of trimethyl-glycine, (CH3)3NCH2COOH (which was described as betaine). An example of a betaine surfactant is laurylamido-propyldimethylbetaine, Ci2H25CON(CH3)2CH2COOH. 

Molyneux, P., Rhodes, C.T. andSwarbrick, J. (1965) Thermodynamics ofmicellization ofN-alkyl betaines. Trans. Faraday Soc, 61, 1043-52. 

The most simple surfactant betaines are alkyl betaines where one of the methyl groups of trimethyl glycine is replaced with a fatty alkyl moiety. Synthetically, they are made by condensing 1 mol of sodium chloroacetate with an alkyldimethylamine to yield the surfactant and 1 mol of sodium chloride by-product (see Figure 6.14). 

Amphoteric surfactants. These compounds have the characteristics of both anionic detergents and cationic fabric softeners. They tend to work best at neutral pH, and are found in shampoos, skin cleaners, and carpet shampoos. They are very stable in strong acidic conditions and are favorably used with hydrofluoric acid. For example, compounds of alkyl-betain or alkylsulfobetaine type possess both anionic and cationic groups in the same molecule even in aqueous solution. These surfactants are rarely employed in laundry detergents because of their high costs [3, 4]. 

Table 1.—Area per head group calculated for d-alkyl betaines using present model,...

Amphoteric Surfactants. Amphoteric surfactants in aqueous solution contain both positive and negative charges in the same molecule. Thus, a hydrophobic fatty chain is attached to a hydrophilic group that contains both positive and negative charges. Its behavior depends on the condition of the medium or its pH value. Examples of this type are the alkyl betaines. 

In general, betaines are compatible with anionic surfactants. The simpler alkyl betaines are found to be less compatible with alkyl sulfates than the alkylamido-propyl betaines, especially when the concentration of betaine is about one half that of the lauryl sulfate [1], This incompatibility is related to the pH of the system as well as the nature of the anionic species present. 

Thompson, R.A. and AUenmark, S. (1992) Factors influencing the micellar catalyzed hydrolysis of long-chain alkyl betainates. /. Colloid Interface Sri., 148, 241-246. 

Fig. 17. Phase diagram of the timolol maieate (0.34 wt%)-EHEC (lwt%>-alkyl betainate-water system (top), and in vitro release of timolol maieate from aqueous solution (1), non-gelling lwt% EHEC solution (2) 1 wt% EHEC gel (3) (bottom) (adapted from [99])...

Alkyl betaine foam booster, mild surfactant for shampoos and detergents. 

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