Tartaric acid, ionization

Grapes are one of the few fruit crops that contain a significant amount of the weak organic acid known as tartaric acid, HOOC-(CHOH)2-COOH. More than half of the acid content of wine is ascribed to tartaric acid. As a weak acid, tartaric acid partially ionizes in water to yield the bitartrate or hydrogen tartrate ion ... 

Natural compounds are also applied as chiral ligands in enantioselective homogeneous metallo-catalysts. A classical example is the Sharpless epoxidation of primary allylic alcohols with tert-butyl hydroperoxide [37]. Here the diethyl ester of natural (R,R)-(+)-tartaric acid (a by-product of wine manufacture) is used as bi-dentate ligand of the Ti(iv) center. The enantiomeric excess is >90%. The addition of zeolite KA or NaA is essential [38], bringing about adsorption of traces of water and - by cation exchange - some ionization of the hydroperoxide. 

Tartaric acid is dibasic (H2tart), carboxyl protons being ionized by pH 5. The hydroxyl groups are not ionized (p/Ca3 14 and pK 15.6).622 The formation constants of ( + )-,(-)-, ( )- and meso-tartaric acids with V02+ confirm binuclear complexes of optically active and, to a lesser extent, meso acids with V02+.623... 

A separation of the ions in acid rain is shown in Fig. 8.7 using conductivity detection. The peaks of the anions (sulfate, chloride and nitrate), which are highly ionized, are positive. The cation peaks are of lower conductivity than the tartaric acid eluent and hence are in the negative direction. The detection limits are low enough to handle most acid rain samples without any preconcentration (Table 8.4). 

The introduction of a double bond leads to an increased activity in the acid. The marked difference between the values of the constants of maleic and fumaric acid is noteworthy. The difference appears to be the result of the positions with respect to each other occupied by the two carboxyl groups. The stereochemical influence is marked in this case. In the tartaric acids this is not so the ionization constants for d-tartaric acid, Z-tartaric acid, and racemic acid are the same, namely,. 097. 

Bates RG and Canham RG, Resolution of the dissociation constants of D-tartaric acid from 0° to 50°, /. Res. Nat. Bur. Stand., 47,343-348 (1951). NB Used an electrochemical cell wiBiout liquid junction potentials. Extrapolated ionic strengBi to zero to give Biermodynamic pX values, which were then used to estimate Bie Biermodynamic functions for ionization. 

The pKg s at room temperature for levallorphan tartrate have been determined by a pH titration with sodium hydroxide to be 4.5 and 6.9 (13). The first pK observed for levallorphan tartrate results from the Ionization of the carboxylic proton from the tartaric acid. The second pKg is due to the ionization of the proton from the ammonium moiety In the levallorphan tartrate. 

Since tartaric acid is a weak acid, we will assume it is not ionized. Letting 2= grams of tartaric acid per 100 grams of water, we obtain... 

Enantiomers have identical physical and chemical properties in achiral environments. The enantiomers of tartaric acid (Table 6.1), for example, have the same melting point, the same boiling point, the same solubilities in water and other common solvents, and the same values of pif (the acid ionization constant), and they all undergo the same acid-base reactions. The enantiomers of tartaric acid do, however, differ in optical activity (the ability to rotate the plane of polarized light), a property that is discussed in the next section. 

Apart from the obligatory membrane filtration (0.45 pm), the only sample preparation in the analysis of rain water, ground water, and swimming pool water is a dilution with de-ionized water. Figure 9-9 shows a cation chromatogram of a rain water sample [42] that applies non-suppressed conductivity detection the sample was injected without any dilution because of its low electrolyte content. Metrosep Cation 1-2 served as the separator column and the eluant was a mixture of tartaric acid and pyridine-2,6-dicarboxylic acid. 

In solution, the racemic tartaric acid may be represented as C02H-(CH0H)2-CO2H, as is indicated by its cryoscopic depression and its ionization constant its solubility is controlled, however, by the molecular complexity of the solid. (See Table VI.)... 

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