Chelating agents tartaric acid

Complexing chelating) agents citric acid, tartaric acid, B sodium tartrate), kerosene, segesterene, sodium citrate, oxalic acid, sodium oxalate, or orthophosphoric acid X... 

Most divalent and trivalent ions, with the exception of the alkaline-earth metals, are effectively chelated by the hydroxycarboxylates citric and tartaric acid, and citric acid will also sequester iron in the presence of ammonia. Another hydroxycarboxylate, gluconic acid, is especially useful in caustic soda solution and as a general-purpose sequestering agent. 

Reaction with chelating agents. Such reactions have been used primarily for partial dealumination of Y zeolites. In 1968, Kerr (8,21) reported the preparation of aluminum-deficient Y zeolites by extraction of aluminum from the framework with EDTA. Using this method, up to about 50 percent of the aluminum atoms was removed from the zeolite in the form of a water soluble chelate, without any appreciable loss in zeolite crystallinity. Later work (22) has shown that about 80 percent of framework aluminum can be removed with EDTA, while the zeolite maintains about 60 to 70 percent of its initial crystallinity. Beaumont and Barthomeuf (23-25) used acetylacetone and several amino-acid-derived chelating agents for the extraction of aluminum from Y zeolites. Dealumination of Y zeolites with tartaric acid has also been reported (26). A mechanism for the removal of framework aluminum by EDTA has been proposed by Kerr (8). It involves the hydrolysis of Si-O-Al bonds, similar to the scheme in Figure 1A, followed by formation of a soluble chelate between cationic, non-framework aluminum and EDTA. 

Oxyacids, like citric or tartaric acids, and polyols, like saccharose are also used, mainly as masking agents, in qualitative analysis. The action of some specific reagents, like oc-a -bipyridyl for iron(II) and dimethylglyoxime for nickel(II), is also based on the formation of chelate complexes. In quantitative analysis the formation of chelates is frequently utilized (complexometric titrations). ... 

Metal chelation Oxygen scavenging and reducing agents Singlet oxygen quenching Cirtic, Malic, Succinic and Tartaric acids Ethylenediaminetetraacetic acid, Phosphates Ascorbic acid, Ascorbyl palmitate, Erythorbic acid. Sodium erythorbate. Sulfites Carotenoids (p-Carotene, Lycopene and Lutein)... 

To decrease hydrolysis and to increase selectivity we have employed complex-forming agents such as DTPA and tartaric acid ( 1 ) The results show that Am extraction in the NaOH-tartaric acid solution is approximately the same as that of Eu. At low concentrations of the alkali the distribution coefficients are small as the concentration increases, the extraction of Am and Eu sharply increases to reach a maximum at 2 M NaOH ( 99%) and to stay constant up to 10 M. The R = f/NaOH/ dependence by Am and Eu extraction in the form of tartrates by aliquat-336 was different, namely the extraction was high at low alkali concentrations and poor at NaOH concentration greater than 2 M. It may be assumed that DOP forms strong chelates with trivalent actinides and lantha-... 

Chelation. Chelating agents, such as EDTA, are added to prevent precipitation of insoluble metal salts. Citric acid and tartaric acid are other chelating agents that are added to prevent discoloration during food processing. 

The Sharpless asymmetric epoxidation (sec. 3.4.D.i) exploits this chelation effect because its selectivity arises from coordination of the allylic alcohol to a titanium complex in the presence of a chiral agent. The most effective additive was a tartaric acid ester (tartrate), and its presence led to high enantioselectivity in the epoxidation.23 An example is the conversion of allylic alcohol 40 to epoxy-alcohol 41, in Miyashita s synthesis of the Cg-Ci5 segment of (-t-)-discodermolide.24 in this reaction, the tartrate, the alkenyl alcohol, and the peroxide bind to titanium and provide facial selectivity for the transfer of oxygen from the peroxide to the alkene. Binding of the allylic alcohol to the metal is important for delivery of the electrophilic oxygen and... 

Haines et al. investigated the stereoselective formation of bisfethyienediamine)-cobaltflll) complexes containing optically active tartaric acid from a reaction of [Co(C03)(en)2]Cl and S(—)-tartaric acid in water at steam-bath temperature, two optically active complexes, A-[Co(S-C4H40g)(en)2] Cl and A-[Co(S-C4H306)(en ], were isolated by TLC with silica gel. In the former complex, the tartrate ion acts as a bidentate chelate agent with one free carboxylic acid (IV), and in the latter the tartrate is trinegative. 

The potential of the thallium reduction is practically unaflEected by chelating agents. The lead wave is shifted to —0.80 V in sodium hydroxide solution. Tin (II) is reduced at —1.26 V in this medium. Alkaline tartrate is often used as the supporting electrolyte. In this medium, lead is reduced at —0.79 V, thallium at —0.50 V, and tin (II) at —1.20 V. In tartaric acid medium, the half-wave potentials are —0.52, 0.49, and —0.68 V, respectively. 

Fig. 3.51 TEM images of the YAG powdos using chelating agents a citric acid, b tartaric acid, c glycine and d EDTA. Reproduced with pramission from [260]. Copyright 2010, Elsevier...

Retardation Hydroxycarboxylic acids and their salts, e.g., citric, tartaric, gluconic, glucoheptonic, maleic, salicylic, tannic Carbohydrates, e.g., glucose, sucrose, hydroxylated polymers (corn starch syrup) Chelating agents, e.g., EDTA, NTA, borates Inorganic salts, e.g., zinc, lead, phosphates... 

Chelating reagents have been used in chelatometric titrations and as masking agents for colorimetric determinations and for separations by precipitation or solvent extraction. This investigation has provided the first indication that the acids are an integral part of the complexes formed with Ti(III). It was found that Ti(III), EDTA, and oxalic acid form a very stable complex of equimolar composition which shows an absorbance maximum at 120 mil. Tartaric acid appears to form a similar type of complex which is much less stable and also shows an absorbance maximum at 720 mp. With this complex, however, the optical absorbance and EPR signal intensity... 

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