Acid-base-coupled

Eyal, A. M. Kogan, L. Bressler, E. Extraction of metal salts by mixtures of water-immiscible amines and organic acids (acid-base couple extractants). 2. Theoretical treatment and analysis. Ind. Eng. Chem. Res. 1994, 33, 1076-1085. 

The redox and proton transfer reactions undergone by the flavin prosthetic group are summarized in Scheme 5.2. The vertical reactions are oxidations by Q regenerating P. From the standard potential values (V vs. SCE) of the four flavin redox couples that are involved in Scheme 5.2 and those of the mediators (Table 5.1), all four oxidation steps may be regarded as irreversible. The horizontal reactions are deprotonations by the bases present in the buffer. From the pA values of the various flavin acid-base couples indicated in Scheme 5.2 (over or below the horizontal arrows), reactions H2 and H4 may be regarded as irreversible and reactions HI and... 

In general, the strength of an acid is measured by its capacity to release H+ ions in water. Other liquids can be used instead of water, like ammonia. We then define an acid-base couple, using the example of hydrochloric acid in aqueous environment (Fig. 3.26). 

For an acid-base couple, the relation is (Fig. 3.29) This allows the definition of the acidity constant of... 

The acid-base couple is the most known because of the massive and ubiquitous use of the acids and bases in work environment as well as in homelife during chemical assaults. But it is not the only cause of ocular irritations or corrosions. An oxidizer or a reducing agent can also generate lesions to tissues. 

ACID EXTRACTION BY ACID-BASE-COUPLED EXTRACTANTS... 

Acid-base-coupled extractants seem to be very attractive for many industrial applications. They allow recovery of acids from waste streams instead of neutralization. Acid and base consumption is thereby reduced, as is the amount of waste to be disposed of. Being also excellent extractants for metal salts, ABC extractants provide for sequential recovery of acids and their salts from waste streams. The extractant composition can be adjusted so that a single extractant can extract first the acid and then the salt at high efficiency, selectivity, and reversibility. Because of this high reversibility, these components are recovered by back-extraction with water, at concentrations approaching those in the feed stream and in some cases even higher. 

E. Bressler and A. M. Eyal, Extraction of ZnSO by acid base couple extractants, Proceedings of Int. Solv. Extr. Conf, 1993, Vol. 1, pp. 549—556. 

Acid-base-coupled extractants (i.e., mixed liquid cation and anion exchangers) promise to be very versatile reagents for the extraction of metal salts, mineral and organic acids, and even amino acids. The extractants are based on ideas presented by Grinstead and coworkers some 30 years ago,... 

Thus pH = — log(cH,b). while cb and chb represent the concentrations of the dissociated and protonated species of the acid-hase chromophore pair, respectively. The quantity pK — F< s/(RTln 10) can be considered as an apparent pK for proton binding of the chromophoric acid-base couple on the membrane surface. Eqn. 5.8 shows that the protonatiou state Cb/chb of the probe is altered if s changes at constant pH, which results in a change in the fluorescence yield. Thus changes of fluorescence at constant bulk pH reflect chauges of aud can be utilised, therefore, to study how molecules interact with membranes. 

A redox indicator is a redox couple whose forms have distinct and characteristic spectra of high molar absorbances. They are frequently acid/base couples as well, making pH control necessary. They are useful in conducting titrations where only the stoichiometry and not the potential values are needed. Several are described below. 

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