Organic chelates

For ink vehicles based on hydroxyl group containing binders such as nitrocellulose and cellulose acetate, the tetraalkyl titanates cross-link the binder prematurely, limiting the storage stabiUty of the printing ink. Chelated organic titanates such as TYZOR AA and TYZOR TE are preferred for use in these cases because they only initiate cross-linking when the ink is heated to temperatures above 80°C (503). 

The chelated organic titanates also function as adhesion promoters of the ink binder to printed substrates such as plastic films, paper, and aluminum foil (504). The acetylacetone complexes of titanium are the preferred products for promoting adhesion of printing inks to polypropylene films. 

Tetraalkyl titanates react with organic borates, B(OR )2, to give complexes of the general formula Ti(OR)4 B(OR )2, which are useful as catalysts and cross-linking agents (562). Mixtures of chelated organic titanates such as TYZOR TE and TYZOR LA with alkaU metal borates, such as borax, or boric acid can be used to produce shear-stable fracturing fluids (563). 

Complexes with chelating organic reagents such as salicylaldehyde and -diketonales were first prepared by N. V. Sidgwick and his students in 1925, and many more have since been characterized, Stability, as measured by equilibrium formation conslanis, is rather low and almost invariably decreases in the sequence Lj > Na > K. This situation changed drainalically in 1967 w hen C. J. Pedersen announced the synthesis of several macrocyclie polyethers which were shown to form stable complexes with... 

Reactions of chelated organic ligands. Q. Fernando, Adv. Inorg. Chem. Radiochem., 1965, 7, 185-261 (210). 

Reactions of Chelated Organic Ligands Quintus Fernando... 

Chelators Organic compounds to which metal ions (e.g., Fe b bind... 

The BF2 chelates are hydrolytically stable (the majority of them may be recrystallized from water) whereas the BC12 chelates are easily hydrolyzed. The boric acid ester complex triptych boroxazolidines are also stable towards hydrolysis as are other aminoalcohol esters.83 A great number of the boron chelates are colored several spectrophotometric methods are based on chelate formation81 84 for the analytical determination of boric acid, organoboric acids and chelating organic compounds. The boron chelates are remarkable for their pharmacological properties as well.84 Various aspects of the boron chelates have been reviewed.81,83-86... 

Using these agents, especially the particularly effective 1 2 complex 4 with salicylic acid, metallization can be carried out easily at high pH without precipitation of inert chromium hydroxide. In certain cases a 1 1 chromium complex that still contains chelating organic acid as ligand can also be obtained. 

Employing this spectrophotometric method we surveyed the reactivity of 1 towards simple and chelating organic substrates the chelating agents employed in this study were the monosubstituted triphenylphosphines (4) ... 

M. L. H. Green and D. L. Jones Reactions of Chelated Organic Ligands... 

Because of the biological importance of many chelating organic molecules such as a-amino acids many of their absolute configurations (determined by the Bijvoet method (57)), are available. This means that the known absolute configuration of one centre in a molecule can be used to deduce that of other centres. This can be done in several ways, and has proved extremely useful in coordination chemistry. 

Fig. 14. From SBU to metallic clusters linked by chelating organic molecules.

A range of other systems of Ga + with chelating organic acids has been studied and solution equilibria data have been obtained. Based on these investigations it is clear that in aU cases basic complexes (i.e. those containing oxo or hydroxo ligands) are involved, and the hydrated hydroxide cation [Ga(OH)] + shows greater reactivity compared with the hydrated ion of Ga +. 

Cram discussed a cyclic model for nucleophilic additions to chiral carbonyl compounds containing an a-alkoxy, a-hydroxy, and a-amino group capable of forming a chelate with the organometallic reagent. Incorporation of chelate organization into the design of stereoselective processes is an important control element in diastereo-selective " and enantioselective carbonyl additions. 

Aerobic respiration, on the other hand, releases CO2 owing to the oxidation of organic matter, and thus, increases the concentration of CO2 in the system. The equilibria of the carbonate buffer system are shifted in the opposite direction and a dissolution of CaCOj results (Fig. 2.1.1, fine arrows). In addition to oxidative respiration, partial degradation (fermen-taton) of organic matter may result in formation of organic acids which also contribute to the dissolution of carbonates. Furthermore, carbonate may be dissolved by the activity of chelating organic compounds, or by the enzyme carbonic anhydrase. 

Fang, T.J. and Tsai, H.C. 2003. Growth patterns of Escherichia coli 0157 H7 in ground beef treated with nisin, chelators, organic acids and their combinations immobilized in calcium alginate gels. Food Microbiology 20 243-253. 

CCA has decades of proven performanee in field trials and in-service. With the correct species and treatment CCA provided an assured in-ground service life in excess of 50 years. Reeently Bull (2001) has proposed that the fixation produets of CCA are dominated by ehromium (III) arsenate, chromium (III) hydroxide and wood-carboxylate-eopper (II) eomplexes. CCA is potent precisely because it is bioavailable - and persistent. Signifieantly the separation of copper from chromium and arsenic is consistent with the observation that acetie aeid and chelating organic acids - and silage or eompost - under eertain eireumstanees ean promote leaching and early failure (Cooper and Ung, 1995 Kazi and Cooper, 1998). 

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