Cationic surfactants general

Anionics are the largest class of surfactants in terms of volume, and include the work-horse surfactants, linear alkylbenzene sulfonate (LAS), alcohol sulfate (AS) and alcohol ether (or ethoxy) sulfate (AES). Cationic surfactants generally include various quaternary salts, used predominantly as fabric conditioners ( fabric softeners ), anti-static agents and anti-microbial agents. Amphoteric surfactants represent the smallest class of surfactants, and generally are used when solubility, mildness and compatibility issues are important. 

PD is an aqueous solution containing silver ions, a ferrous/ferric redox (reduction/oxidation) system, a buffer (citric acid), and a cationic surfactant (generally -dodecylamine acetate). The ferrous (Fe ) ions in solution reduce the silver (Ag +) ions to silver metal (Ag°), with ferric (Fe + ) ions being present to hold back the reaction (eqn [1]) ... 

Higher order aUphatic quaternary compounds, where one of the alkyl groups contains - 10 carbon atoms, exhibit surface-active properties (167). These compounds compose a subclass of a more general class of compounds known as cationic surfactants (qv). These have physical properties such as substantivity and aggregation ia polar media (168) that give rise to many practical appHcations. In some cases the ammonium compounds are referred to as iaverse soaps because the charge on the organic portion of the molecule is cationic rather than anionic. 

Microscopic sheets of amorphous silica have been prepared in the laboratory by either (/) hydrolysis of gaseous SiCl or SiF to form monosilicic acid [10193-36-9] (orthosihcic acid), Si(OH)4, with simultaneous polymerisation in water of the monosilicic acid that is formed (7) (2) freesing of colloidal silica or polysilicic acid (8—10) (J) hydrolysis of HSiCl in ether, followed by solvent evaporation (11) or (4) coagulation of silica in the presence of cationic surfactants (12). Amorphous silica fibers are prepared by drying thin films of sols or oxidising silicon monoxide (13). Hydrated amorphous silica differs in solubility from anhydrous or surface-hydrated amorphous sdica forms (1) in that the former is generally stable up to 60°C, and water is not lost by evaporation at room temperature. Hydrated sdica gel can be prepared by reaction of hydrated sodium siUcate crystals and anhydrous acid, followed by polymerisation of the monosilicic acid that is formed into a dense state (14). This process can result in a water content of approximately one molecule of H2O for each sdanol group present. 

Ethoxylation of alkyl amine ethoxylates is an economical route to obtain the variety of properties required by numerous and sometimes smaH-volume industrial uses of cationic surfactants. Commercial amine ethoxylates shown in Tables 27 and 28 are derived from linear alkyl amines, ahphatic /-alkyl amines, and rosin (dehydroabietyl) amines. Despite the variety of chemical stmctures, the amine ethoxylates tend to have similar properties. In general, they are yellow or amber Hquids or yellowish low melting soHds. Specific gravity at room temperature ranges from 0.9 to 1.15, and they are soluble in acidic media. Higher ethoxylation promotes solubiUty in neutral and alkaline media. The lower ethoxylates form insoluble salts with fatty acids and other anionic surfactants. Salts of higher ethoxylates are soluble, however. Oil solubiUty decreases with increasing ethylene oxide content but many ethoxylates with a fairly even hydrophilic—hydrophobic balance show appreciable oil solubiUty and are used as solutes in the oil phase. 

Nearly all nonionic surfactants contain the same type of hydrophobes as do anionic and cationic surfactants, with solubilisation and surfactant properties arising from the addition of ethylene oxide to give a product having the general formula 9.40. Usually, depending on the... 

Polyamide and polyester fibres are generally scoured using an alkyl poly(oxyethylene) sulphate and sodium carbonate. Some polyester qualities are subjected to a causticisation treatment with sodium hydroxide in the presence of a cationic surfactant to give a lighter fabric with a silkier handle [154,156]. This treatment involves etching (localised saponification) of the polyester surface and is broadly analogous to the S-finish used on triacetate fibres. The process has attracted considerable interest in recent years but its... 

Surfactants, not surprisingly, exert a highly significant influence on the fluorescence of FBAs in solution. This effect is associated with the critical micelle concentration of the surfactant and may be regarded as a special type of solvent effect. Anionic surfactants have almost no influence on the performance of anionic FBAs on cotton, but nonionic surfactants may exert either positive or negative effects on the whiteness of the treated substrate [33]. Cationic surfactants would be expected to have a negative influence, but this is not always so [34]. No general rule can be formulated and each case has to be considered separately. 

Generally speaking imidazole is the nucleophilic functional group, and many of the chiral surfactants are histidine derivatives (Brown and Bunton, 1974 Brown et al., 1981). In other cases mixed systems have been used, e.g. an inert cationic surfactant plus a chiral amphiphilic histidine or hydroxa-... 

Numerous applications have been shown to exist that overcome the general problems of lack of volatility and instability at higher temperatures that principally hamper direct analysis of surfactants by GC methods. Thus, a whole suite of derivatisation techniques are available for the gas chromatographist to successfully determine anionic, non-ionic and cationic surfactants in the environment. This enables the analyst to combine the high-resolution chromatography that capillary GC offers with sophisticated detection methods such as mass spectrometry. In particular, for the further elucidation of the complex mixtures, which is typical for the composition of many of the commercial surfactant formulations, the high resolving power of GC will be necessary. 

Quaternary fluorinated alkyl ammonium compounds The fluorine-containing cationic surfactants of quat type with the general formula C F2 , 1-S02-NH-CH2-CH2-CH2-N (CH3)3 X (n = 8) (Fig. 2.12.1(d)) were examined by FIA—MS using APCI and ESI in the positive and negative modes. The APCI(- -/—) ionisation resulted in a dealkylation at the nitrogen with ions at m/z 585 or 583, respectively. The alkyl chain of this compound contained the moiety C8Fi7. The ions generated under APCI conditions were characterised as dealkylation products—m/z 585 [M — CH2]+ or m/z 583 [M — H— CH3] —as reported in the literature [35,37]. 

Fig. 2.12.6. Identification of esterquat compounds FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of selected [M — RCO]+ base peak ion of cationic surfactant blend of di-hydrogenated tallowethyl hydroxyethyl ammonium methane sulfate type (mlz 692 general formula (R(C0)0CH2CH2)2-N (CH3)-CH2CH2(0H)CH30S03) fragmentation behaviour under CID...

Cationic surfactant blends of quats were studied by FIA-ESI-MS(+). The general formula of the compounds was (R)nN (CH3)4 n with R = C12-C22. These compounds applied in products for personal... 

The cationic surfactant mixture, which was also observed by FIA— MS(+) in the Saale River (Germany) but could not be separated under RP-Cis conditions, was classed as a cationic surfactant mixture of fatty acid ethoxy amine type with the general formula R-N H((CH2-CH2-OH)x)-(CH2-CH2-OH)yX- by FIA-MS-MS(+) [29], The CID spectrum of the parent ion at m/z 538 generated by FIA-MS-MS(+) resulted in a series of equally spaced product ions (A m/z 44) starting with 212 and ending at 520. Besides these product ions, alkyl- and ethoxylate fragment ions with low intensity were observed at 57, 71... 

Fig. 2.12.15. FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of cationic surfactant compound (m/z 538) fatty acid polyglycol amine type observed in the Saale river, Germany (general formula R—N H((CH2—CH2—OH)x)—(CH2—CH2—OH)y X fragmentation behaviour of [M]+ parent ion at m/z 538 under CID conditions is presented...

The increasing popularity of biodegradable materials, which are more susceptible to microbial attack, has boosted the demand for preservation. If the product does not already contain ingredients that are themselves preservatives, such as cationic surfactants, acids, or bases, preservatives may need to be added. The required level of preservatives can be related to water availability (AW), which is defined as the ratio between the water vapor pressure over a substance and the water vapor pressure over pure water at the same temperature [17], In general, an A W of below 70% should be targeted to prohibit microorganism growth [18],... 

Each surfactant molecule includes a hydrophobic, nonpolar portion, and a hydrophilic, polar portion. The polar portion is either nonionic (neutral), anionic (negatively charged), or cationic (positively charged). For more information on surfactants see T0759, Surfactants—General. 

Glasses exist that fnnction as selective electrodes for many different monovalent and some divalent cations. Alternatively, a hydrophobic membrane can be made semiper-meable if a hydrophobic molecnle called an ionophore that selectively binds an ion is dissolved in it. The selectivity of the membrane is determined by the structnre of the ionophore. Some ionophores are natnral products, such as gramicidin, which is highly specific for K+, whereas others such as crown ethers and cryptands are synthetic. Ions such as, 1, Br, and N03 can be detected using quaternary ammonium cationic surfactants as a lipid-soluble counterion. ISEs are generally sensitive in the 10 to 10 M range, but are not perfectly selective. The most typical membrane material used in ISEs is polyvinyl chloride plasticized with dialkylsebacate or other hydrophobic chemicals. 

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