Amphoterism of L-acids

In binary liquid mixtures of the so-called aprotic acids (Lewis acids or L-acids) formed by halogenides of metals of III-IV groups of the periodic system, there are often cases when one of the components is an anion-donor (base) and the second component is an anion-acceptor (acid)  

The following is an example of eq. [9.12] In the mixture ASCI3 - SnCl4, stannous tetrachloride is a base and arsenic trichloride is an aeid  

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Oda18 investigated photostabilization by amphoteric counterions such as zinc salts of l-hydroxy-2-naphthoic acid and its derivatives. They were very effective in stabilizing the colored forms of spirooxazines (see Figure 2.3). 

A synthesis of electrochemically amphoteric TTFAQ-ct-A derivatives 917 and 918 (TTFAQ = 9,10-bis(l,3-dithiol-2-ylidene)-9,10-dihydroanthracene, ct = saturated spacer, A = polynitrofluorene acceptor) involved esterification of the acid chloride 916 with the hydroxymethyl-substituted TTFAQ derivative 915 in pyridine. To increase acceptor properties, 917 was converted into the dicyanomethylene derivative 918 by reaction with malononitrile in DMF (Scheme 138) <2002JA14227>. 

Solutions of any desired pH may be obtained simply by mixing a weak acid or base with one of its salts in various proportions. It is evident from equation (48) that even small amounts of strong acids and bases have only a slight effect on the pH of such mixtures. Certainly the small quantities of alkali from glass and carbon dioxide from the atmosphere can exert no perceptible influence. Such mixtures which are resistant to a change in reaction were called Buffer Mixtures by S. P. L. SOkensen. L. Michaelis coined the term Regulators. They may also be referred to as Ampholytes because of the amphoteric character of such mixtures. AU mixtures of weak adds and their salts,... 

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. 

Amphoterism phenomenon is the mechanism of acid-base interaction in systems formed by H-acids or two L-acids in binary systems. For example, in stannous tetrachloride-carboxylic acid system, acid-base interaction occurs with SnCl4 being an acid ... 

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. 

Hitchcock, D., Amphoteric Properties of Amino Acids and Proteins. In C.L.A. Schmidt, Chemistry of the Amino Acids and Proteins, p. 596. C. C Thomas, Springfield, Illinois 1938. 

The use of l-butyl-3-methylimidazolium of varying anion chaotropicity as a mobile phase additive for separation and chromatographic behavior studies of acidic, basic, and amphoteric compounds in reversed phase liquid chromatography has been reported (23). Two hydrophobic columns were used Zorbax XDB-C18 and Zorbax SB-Phenyl. Satisfactory separations could be achieved by the use of carefully optimized chromatographic systems modified with the additive. 

Arens, M., R. Spilker, Fatty acid amidopropylbetaines—determination of fatty acid amidopro-pylamine—collaboration of the DGF. Communication 150 German standard methods for study of fats, fatty products, surfactants and related materials. Communication 116 Analysis of surface active materials XXV (in German), Fett Wiss. TechnoL, 1995, 97,468-470. Schwarz, G., P. Leenders, U. Ploog, Condensation products of fatty acids or their methyl esters with aminoethylethanolamine (in German), Fette, Seifen, Anstrichm., 1979,81, 154-158. Takano, S., K. Tsuji, Structural analysis of the amphoteric surfactants obtained by the reaction of l-(2-hydroxyethyl)-2-alkyl-2-imidazoline with ethyl acrylate,/. Am. Oil Chem. Soc., 1983, 60,1798-1806. 

Lead Monoxide. Lead monoxide (litharge), PbO, occurs as a reddish alpha form, which is stable up to 489°C where it transforms to a yellow beta form (massicot). The latter is stable at high temperatures. The solubihty of a-PbO ia water is 0.0504 g/L at 25°C the solubihty of the p-PbO is 0.1065 g/L at 25°C (40). Lead monoxide is amphoteric and dissolves ia both acids and alkahes. In alkahes, it forms the plumbite ion PbO - The monoxide is produced commercially by the reaction of molten lead with air or oxygen ia a furnace. Black or gray oxide is manufactured by the Barton process, by the oxidation of atomized molten lead ia air, as well as by the ball mill process, ia which metallic lead balls of high purity are tumbled ia the mill to form partially oxidized lead particles. 

M. L. Braden. Preparation of amphoteric acrylic acid copolymers suitable as oil-in-water emulsion breakers. Patent US 5552498,1996. 

For some strong electron donor molecules the polarization of the X2 molecule may be sufficient that the X atom not complexed to B serves as an electron donor to a second X2 molecule, i.e., the dihalogen is amphoteric , acting as a Lewis acid to Lewis base B, and as a Lewis base to the second X2 molecule, acting as a Lewis acid. For a 1 1 B X2 X2 ratio, an extended adduct (Fig. 1, mode AA) is formed, as illustrated in Fig. 2c for 4,5-bis(bromomethyl)-l,3-dithiole-2-thione-diiodine diiodine (HAMCAA) [58]. This is often referred to as an extended spoke structure. If the second X2 acts as Lewis acid acceptor at either end of the molecule, then a bridged amphoteric adduct (Fig. 1, mode BA) is formed, as illustrated for (acridine I2)2 I2 (QARGIZ) [31] in Fig. 2d. 

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