Chelate reagents

Chelating reagents in solvent extraction processes the present position. A. W. Ashbrook, Coord. Chem. Rev., 1975,16, 285-307 (74). 

The preparation of neutral chelates for the separation of etals by gas chromatography has been studied for many years [436,667,669-672]. The principal limit to the success of this approach is the paucity of suitable reagents which can confer the necessary volatility, thermal stability and chemical inertness on the metal ions. The class of metal chelating reagents that have... 

Similar results are obtained with (3-methoxyketones using TiCl4 as the chelating reagent.134... 

A knowledge of the extraction equilibria between the organic and aqueous phases helps to identify the operational variables that can control the solvent extraction process. An example - the extraction of copper from a copper sulfate solution using a chelating reagent (HR) - is considered. This is one of the best studied examples of solvent extraction. Normally, the system would not be described as a water-hydrocarbon dual-phase system, as it is in fact the Cu2+, SO-, H+, R-, and R-, and the equation... 

Miyahara, T., Kitamura, H., Narita, K., and Toyo oka, T., Ion-exchange chromatography of aluminum using 3-carboxy-2-naphthylamine-N,N-diacetic acid as a fluorescent post-column chelating reagent, Biomed. Chromatogr., 13, 70, 1999. 

Figure 20.18 The bifunctional chelating reagent DTPA may be used to modify amine groups on antibody molecules, forming amide bond linkages. Indium-111 then may be complexed to the chelator group to create a radiolabeled-targeting reagent.

Sasagawa, M. Nosaka, Y. 2001. Studies on the effects of Cd ion sources and chelating reagents on atomic layer CdS deposition by successive ionic layer adsorption and reaction (SILAR) method. Phys. Chem. Chem. Phys. 3 3371-3376. 

Three causes of extractant solubility in the aqueous phase may be distinguished solubility of un-ionized and ionized extractant and metal-extractant species. For extractants such as acids, amines, and chelating reagents, their polar character will always result in some solubility in the aqueous phase over the pH range in which they are useful for metal extraction. Solubility depends on many factors including temperature, pH, and salt concentration in the aqueous phase, as discussed in Chapter 2. 

We named this catalyst modified catalyst instead of poisoned catalyst, because the effect of treatment with the chelate reagents on the activity of the catalyst depended on the nature of the substrate. 

Since RNi contains a large amount of aluminum and 2-hydroxy acid is a strong chelating reagent, one difference between RNi and RNiA could be ascribed to their difference in aluminum contents. Table XII (49) shows the correlation between the aluminum content and the EDA of those catalysts modified with tartaric acid. The aluminum content of RNi was decreased by pretreatment with hydroxy acid. Moreover, reduced nickel prepared from NiO (HNi-1) gives an effective modified catalyst and its pretreatment with hydroxyacid does not affect its EDA. 

This procedure serves two purposes. It provides a synthesis for the important chelating reagent 2,2 -bipyridine, a substance of interest in several fields of chemistry, and it gives a preparation of an active, degassed Raney nickel catalyst. 

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