Quaternary ammonium salts with amphoterics

The possible procedures involving titration with SDS or BEC all depend on pH control, and are therefore not applicable to mixtures containing alkali-labile quats. It is better to assume that such mixtures will necessitate separation, and the guidelines given below assume that alkali-labile quats are absent, and that only one quat and one amphoteric are present, although the astute analyst will be able to work out schemes for some mixtures containing more than one surfactant of each class. 

As before, potentiometric titration may sometimes be more successful than two-phase, and acid and alkaline solutions must be at least 0.1 M in or OH. Because of the variety of structures possible in amphoterics, it is advisable to confirm the practicability of these suggested procedures in individual cases. It is assumed that all amphoterics contain only one acidic and one basic group. Similar procedures may be applicable in other cases, but would need to be investigated by experiment. 

Titration with SDS and BEC. Titration in acid and alkaline solution gives the kinds of measurement shown in Table 8.1. 

Titration with NaTPB. Mixtures of quats and WW or WS amphoterics can be analysed by titration in acid solution and at pH 10. 

Potentiometric acid-base titration. With reservations about the effects of other weak acids and bases, amphoterics can be determined in any mixture with quats by potentiometric acid-base titration in ethanol or propan-2-ol. WW amphoterics consume two mols of acid or base per mol. WS and SW amphoterics consume one mol per mol. Mixtures can be 

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Anionic (sulphate or sulphonate) Amphoteric excluding betaine (WW) Quaternary ammonium salt Betaine, amine, amine oxide Sulphobetaine with strongly basic N Nonionic... 

Our group designed and synthesized a new elass of amino acid-based gemini surfactants of the bis(Quats) type (quaternary ammonium salt) (Scheme 2). These consist of 2 hydrophobic chains of 12 carbon atoms, 2 quaternary ammonium groups, and 1 spacer chain containing amide and disulfide bonds [63,64], They derived from the condensation of 7V-dodecyl-A, A -dimethylgly-cine (a well-known soft amphoteric surfactant) with amino acid derivatives containing disulfide bonds, i.e., cystine 1 and cystamine 2 (Scheme 2). 

The asymmetrical tertiary amines are used exclusively as starting materials for the manufacture of quaternary ammonium compounds, cationic and amphoteric surfactants, and amine oxides. Quaternary ammonium compounds used as bactericides and algicides are produced by the reaction of tertiary amines with benzyl chloride, methyl chloride, or dimethyl sulfate. Of these, the benzyl ammonium chloride salt is the most widely used. 

Epichlorohydrin (ECH) is an effective linking group between tertiary amines and acid salts and is used to produce sulfonated amphoterics known as sulfobetaines. Sodium sulfite is reacted with epichlorohydrin in water to produce a solution of l-chloro-2-hydroxypropane sulfonate, which is further reacted with a tertiary amine to yield a quaternary ammonium group linked to the hydroxy-propane sulfonate, with sodium chloride as the primary by-product. Reaction of ECH with partially neutralized phosphorous or phosphoric acid produces an intermediate, which when reacted with tertiary amines yields the respective phosphitobetaines or phosphatobetaines. 

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