Acid-labile surfactants

Acid-labile surfactant conjugates, 214 Azlnphos-methyl, microencapsulated... 

The presence of high SDS concentrations in the excised gel spots is not favourable, because SDS may significantly suppress the signal in ESI-MS. Various tools were developed to remove SDS prior to LC-MS (Ch. 17.4.2). Alternatively, an acid-labile surfactant (ALS) can be applied instead of SDS [14]. 

Proteomics can be broadly defined as the identification, localization, and functional analysis of the protein make-up of cells. One of the major challenges faced, however, is lengthy sample preparation. Several methods have been developed to address this issue including the use of immobilized enzymes and acid-labile surfactants. Microwave heating can also play a valuable role. 

Cyclic 1,3-dioxolane (five-membered ring) and 1,3-dioxane (six-membered ring) compounds, illustrated in Figure 17.8, were early examples of acid-labile surfactants. They are typically synthesized from a long-chain aldehyde by reaction with a diol or a higher polyol. Reaction with a vicinal diol gives the dioxolane, while 1,3-diols yield dioxanes. 

Wu F, Sun D, Wang N, et al. Comparison of surfaetant-assisted shotgun methods using acid-labile surfactants and sodium dodecyl sulfate for membrane proteome analysis. Anal Chim Acta. 2011 698 36 3. doi 10.1016/j.aca.2011.04.039. 

Direct reductions of organohalide pollutants have been done in solutions containing ionic and nonionic surfactants [41], but often with low current efficiencies. One interesting approach involved the use of an acid-labile nonionic surfactant, 1% oil, and water for the dechlorination of hexachlorobenzene. This allowed facile... 

The ester bond is the typical linkage to use in the design of alkali-labile surfactants. The concept is by no means new. Poly(ethylene glycol) (PEG) esters of fatty acids have been around for a long time. They are produced by ethoxylation of the fatty acid the product obtained is a mixture of roughly... 

Jaeger et al. have studied the kinetics of hydrolysis of cationic ketal-based surfactants [41], A comparison was made between acid hydrolysis of surfactants in nonaggregated form and in the form of either micelles or vesicles. (Ketal surfactants with one hydrophobic tail formed micelles and those with two hydrophobic tails formed vesicles.) It was found that both types of aggregation caused about two orders of magnitude reduction of the hydrolysis rate. Aggregation is evidently a way to protect these acid-labile cationic species from acid hydrolysis just as aggregation is a way to speed up alkaline hydrolysis of cationic alkali-labile surfactants, such as esterquats. 

SFC-FID is widely used for the analysis of (nonvolatile) textile finish components. An application of SFC in fuel product analysis is the determination of lubricating oil additives, which consist of complex mixtures of compounds such as zinc dialkylthiophosphates, organic sulfur compounds (e.g. nonylphenyl sulfides), hindered phenols (e.g. 2,6-di-f-butyl-4-methylphenol), hindered amines (e.g. dioctyldiphenylamines) and surfactants (sulfonic acid salts). Classical TLC, SEC and LC analysis are not satisfactory here because of the complexity of such mixtures of compounds, while their lability precludes GC determination. Both cSFC and pSFC enable analysis of most of these chemical classes [305]. Rather few examples have been reported of thermally unstable compounds analysed by SFC an example of thermally labile polymer additives are fire retardants [360]. pSFC has been used for the separation of a mixture of methylvinylsilicones and peroxides (thermally labile analytes) [361]. 

With these results in hand, we have next introduced new types of Lewis acids, e.g scandium tris(-dodecyl sulfate) (4a) and scandium trisdodecanesul-fonate (5a) (Chart 1).[1S1 These Lewis acid-surfactant-combined catalysts (LASCs) were found to form stable colloidal dispersions with organic substrates in water and to catalyze efficiently aldol reactions of aldehydes with very water-labile silyl enol ethers. 

Hydrolysis of acetals yields aldehydes, which are intermediates in the biochemical /3-oxidation of hydrocarbon chains. Acid catalyzed hydrolysis of unsubstituted acetals is generally facile and occurs at a reasonable rate at pH 4-5 at room temperature. Electron-withdrawing substituents, such as hydroxyl, ether oxygen, and halogens, reduce the hydrolysis rate, however [50]. Anionic acetal surfactants are more labile than cationic [40], a fact that can be ascribed to the locally high oxonium ion activity around such micelles. The same effect can also be seen for surfactants forming vesicular aggregates. 

Production of phenol and acetone is based on liquid-phase oxidation of isopropylbenzene. Synthetic fatty acids and fatty alcohols for producing surfactants, terephthalic, adipic, and acetic acids used in producing synthetic and artificial fibers, a variety of solvents for the petroleum and coatings industries—these and other important products are obtained by liquid-phase oxidation of organic compounds. Oxidation processes comprise many parallel and sequential macroscopic and unit (or very simple) stages. The active centers in oxidative chain reactions are various free radicals, differing in structure and in reactivity, so that the nomenclature of these labile particles is constantly changing as oxidation processes are clarified by the appearance in the reaction zone of products which are also involved in the complex mechanism of these chemical conversions. 

These Lewis acid-surfactant-combined catalysts (LASCs) were found to form stable colloidal dispersion systems with organic substrates in water and efficiently catalyze aldol reactions of aldehydes with very water-labile silyl enol ethers. 

Using the same concept outlined above, we were able to study the permeation of copper(II) ions across artificial liposomes made of cationic surfactants [68]. For this purpose, we synthesized the ester surfactant (19). The ester functional group in this case is a derivative of picolinic acid, a molecule known for its hydrolytic lability in the presence of transition metal ions [69] [copper(II) in particular] even at a pH close to neutrality. Vesicles made of cationic surfactants 2Ci6Br, 2Ci8Br and 2Ci6GlyBr containing 10% (molar ratio) of the ester surfactant (19) were obtained by sonication at pH 5. Upon... 

Amphiphiles with an acid- or alkali-labile bond constitute the most widely explored routes to achieve cleavable surfactants. However, other approaches have also been taken. For instance, several types of surfactants with UV-labile bonds have been synthesized and evaluated. Photochemical cleavage yields non-surface-active species and the concept is attractive because it allows an extremely fast breakdown of the surfactant to occur. 

The broad class of products described as sulfonates results from reactions that create a carbon-sulfur bond and utilizes sulfur VI reagent SO3 and its derivatives and adducts such as sulfuric acid. A smaller number of sulfonate products are prepared using sulfur IV reagent SOj as well as its derivatives and adducts such as sodium bisulfite. The preparation of sulfate esters involves the creation of carbon-oxygen-sulfur bonds, and can utilize SO3, sulfuric acid, or chlorosul-fonic acid to form alcohol sulfates that are labile and susceptible to hydrolysis in the presence of water as well as elimination reactions at elevated temperatures, and must be handled under milder conditions than sulfonates during formation and neutralization. Numerous older reviews and recent publications exist covering sulfonation and sulfation processes to produce surfactant products. " ... 

Up to early 1990s, it was assumed that oxyethylation can occur only when the hydrophobic reagent had a labile hydrogen [1-3,5]. Thus, fatty acid methyl esters (FAME) were not considered as a raw material for the direct synthesis of nonionic surfactants with a polyoxyethylene chain. However, esters of fatty acids and PEG monomethyl ethers were known and their properties were described [6]. They were synthesized in a two-step process. Methanol was oxyethylated to PEG monomethyl ether that was then converted into the final product by transesterification with FAME or by esterification with fatty acids, carried out in the presence of an alkaline B or an acid catalyst, respectively. Esters of typical nonionics were synthesized in similar ways and their properties were described [7-9]. 

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