Selective sequestering agents

Supported scavengers are reactive species that selectively quench and/or sequester by-products of the reaction or remove any excess starting materials, and are subsequently removed by filtration (Fig. 2.2). These species, which allow hquid-solid phase extraction are also often referred to as sequestering agents or quenching agents . 

Casein may be coagulated and recovered as rennet casein by treatment of milk with selected proteinases (rennets). However, one of the caseins, K-casein, is hydrolysed during renneting and therefore the properties of rennet casein differ fundamentally from those of acid casein. Rennet casein, which contains the colloidal calcium phosphate of milk, is insoluble in water at pH 7 but can be dissolved by adding calcium sequestering agents, usually citrates or polyphosphates. It has desirable functional properties for certain food applications, e.g. in the production of cheese analogues. 

H. van Bekkum, Studies on selective carbohydrate oxidation, in F. W. Lichtenthaler (Ed.), Carbohydrates as Organic Raw Materials, Wiley-VCH, Weinheim, 1991, pp. 289-310. A. C. Besemer and H. van Bekkum, Calcium sequestering agents based on carbohydrates, in H. van Bekkum, H. Roper, and F. Voragen (Eds.), Carbohydrates as Organic Raw Materials III, Wiley-VCH, Weinheim, 1996, pp. 273-293. 

Selection rules 132 Laporte 132 spin 132 Self-assembly 90 Sepulchrate ligand 56 Sequestering agent 16 Shielding, electrons 20 Soft ligand 78 Soft metal 78 Solid angle factor 85 Solid angle sum 85 Spectrochemical series 112 Spin-only formula 146 Spin selection rule 132 Square planar complexes 108... 

Table VIIL pM values for selected metal ion sequestering agents...

The goods are entered into a bath containing 2-3 volume H O, 1 g/1 sodium hydroxide flake, 0.2 g/1 peroxide stabiliser, 0.25 g/1 sequestering agent and 0.002 to 0.05 g/1 free radical suppressor at 40 C, the temperature is raised to 85 C and then the treatment continued for 1 h. The treated goods are then cooled and rinsed thoroughly. When appropriate, selected optical brighteners may be incorporated in the peroxide bleach bath. 

Studies on the aerobic oxidation of sucrose with noble metal catalysts revealed low selectivity and, surprisingly, the involvement of all of the three primary alcoholic functions at Cg, Ci, and Cg while preserving the disaccharide backbone (Figure 21.12). This is not a problem, because mono- and polycarboxylated sugars are both economically attractive as biodegradable calcium sequestering agents ... 

For larger scale synthesis of this new and because of its vanadium selectivity extremely interesting sequestering agent the reaction of 2-bromopropionic acid has been chosen. L-HIDP can be obtained stereoselectively by condensation of hydroxyl-amine with D-bromopropionic acid (Fig. 4). The enantiomeric purity and comparison of educts and products again can be checked by chromatography on Chirasil-Val. L-HIDP from amavadin is identical in all properties with the synthesized L-HIDP. 

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