Amphoteric Zwitterionic

Amphiphile-oil-water system, temperature of, 16 424-426 Amphiphiles, 16 420 Amphiphile strength, 6 424 Amphiphilic chemicals, 17 56 Amphiphilic copolymers, 20 482 behavior of, 20 483 well-defined, 20 485-490 Amphiphilic molecules, 15 99-101 Amphiphilic plasticizers, 14 480 Amphiphilic polymer blend, 23 720 Amphiphilic polymers statistical, 20 484-490 stimuli-responsive, 20 482-483 Ampholytes, 9 746-747 Amphoteric cyclocopolymers, water-soluble, 23 721 Amphoteric starches, 4 722 Amphoteric (zwitterionic) surfactants, 24 148... 

Surfactants, 9 22-23, 784. See also Surface-active agents admixture for cement, 5 485 amphoteric, 14 709 amphoteric (zwitterionic), 24 148 anionic, 24 144-146 applications for, 24 119, 155-161... 

U.S. 6306805 (2001) Bratescu et al. (Stepan) Anionic-cationic bridging surfactant blends bridging surfactants selected from ethoxylated alkanolamide, semipolar nonionic, amphoteric, zwitterionic Clear solutions at a variety of concentrations in water impart cleaning, foaming, and conditioning properties to hair... 

Anionic, cationic, amphoteric, zwitterionic surfactants thickening agents benefit agents (silicones, fats and oils, vitamins, plant extracts, sunscreens, alkyl lactate, essential oils, etc.) small amount of soap... 

Kai and Ka2 values are frequently tabulated for amino acids (see Table C.l in Appendix C). The values listed represent the successive ionization of the protonated form (i.e., the conjugate acid of the zwitterion) it ionizes to give first the amphoteric zwitterion and second to give the conjugate base, which is the same as a salt of a weak acid that hydrolyzes. Acid-base equilibria of amino acids are therefore treated just as for any other diprotic acid. The hydrogen ion concentration of the zwitterion is calculated in the same way as for any amphoteric salt, such as HC03, as we described in Chapter 7 that is. 

As mentioned in Chapter 1, there can be thousands of molecules with polar heads and nonpolar tails, usable as surfactants. The applications are also many. Thus, the commercial anionic surfactants, recording about 50% of all surfactant production, are literally used all over the place shampoos, dishwashing detergents and washing powders are some common examples. Cationic surfactants likewise are used in hair-conditioners, fabric softeners, asphalt coating, corrosion inhibitor formulations for metal surfaces etc. The major applications of non-ionic surfactants are in the areas of food and drinks, as also pharmaceuticals and cosmetics. Amphoteric /zwitterionic surfactants have only limited applications one area is cosmetics, especially skin care products. 

Column 3 strongly basic anion exchanger hydroxide. Retains SW amphoterics. Elute with acid, as before, to neutralise the resin and render the amphoteric zwitterionic. 

Solutions of polyelectrolytes contain polyions and the free (individual) counterions. The dissociation of a polyacid or its salt yields polyanions, and that of a polybase or its salt yields polycations, in addition to the simple counterions. The polyampholytes are amphoteric their dissociation yields polyions that have anionic and cationic functions in the same ion and often are called zwitterions (as in the case of amino acids having HjN and COO groups in the same molecule). Such an amphoter will behave as a base toward a stronger acid and as an acid toward a stronger base its solution properties (particularly its effective charge) will be pH dependent, and an isoelectric point (pH value) exists where anionic and cationic dissociation is balanced so that the polyion s charges add up to zero net charge (and solubility is minimal). 

As mentioned in Table 8.1, amphoteric surfactants contain both an anionic and a cationic group. In acidic media they tend to behave as cationic agents and in alkaline media as anionic agents. Somewhere between these extremes lies what is known as the isoelectric point (not necessarily, or even commonly, at pH 7), at which the anionic and cationic properties are counterbalanced. At this point the molecule is said to be zwitterionic and its surfactant properties and solubility tend to be at their lowest. These products have acquired a degree of importance as auxiliaries in certain ways [20-25], particularly as levelling agents in the application of reactive dyes to wool. 

Some amphoteric softeners such as amino acids (10.237) and sulphobetaines (10.238) are more effective and durable than the nonionic types but less durable than the cationics moreover, they tend to be expensive. Other amphoteric types include the zwitterionic forms of quaternised imidazolines (10.239) long-chain amine oxides (10.240) also exhibit softening properties. 

When proteins undergo hydrolysis, you wind up with 22 a amino acids, 20 of which are regulcir amino acids and 2 of which are derived amino acids. Amino acids are amphoteric (they possess the characteristics of both acids and bases and can react as either) because both acidic and basic groups are present. An internal acid-base reaction produces a dipolar ion known as a zwitterion (you can see the general structure of one in Figure 16-33). 

Fig.1 The amphoteric behaviour of the zwitterion [Co (T -C5H4COOH)(ri -C5H4COO)] depends on the presence of one -COOH group, which can react with bases, and one -COO group, which can react with acids...

In summary, the organometallic zwitterionic system [Co (t -C5H4COOH)-(t -C5H4COO)] behaves as a reversible amphoteric sink towards a variety of hydrated vapours of acids and bases. 

Amphoteric (or zwitterionic) surfactants carry a positive and a negative charge so that the net charge is zero. Some lipids, such as phophatidylcholine, are zwitterionic. Since lipids are practically not soluble in water, in a strict sense they do not belong to the class... 

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