Catalysts cation-binding properties

A good deal of work has been done on polymeric crown ethers during the last decade. Hogen Esch and Smid have been major contributors from the point of view of cation binding properties, and Blasius and coworkers have been especially interested in the cation selectivity of such species. Montanari and coworkers have developed a number of polymer-anchored crowns for use as phase transfer catalysts. Manecke and Storck have recently published a review titled Polymeric Catalysts , which may be useful to the reader in gaining additional perspective. 

Cation-Binding Properties of Crown Ethers, Lariat Ethers, Bibracchial Lariat Ethers, and Poly(ethylene glycols) as Potential Phase-Transfer Catalysts... 

Kubisa et al. also used hydroxy-functional PEG after reaction with 2-bromo-propionyl bromide as an ATRP macroinitiator [228]. Their goal, however, was to polymerize ferf-butyl acrylate, rather than St, then to hydrolyze the esters to acid functionality and study the cation binding properties of the doubly amphiphilic block copolymers. They utilized a CuBr/PMDETA catalyst system for the polymerization and, although the macroinitiator was completely consumed, MALDI-TOF analysis indicated that bromine was replaced with a hydrogen at... 

Deamidation of soy and other seed meal proteins by hydrolysis of the amide bond, and minimization of the hydrolysis of peptide bonds, improves functional properties of these products. For example, treatment of soy protein with dilute (0.05 A/) HCl, with or without a cation-exchange resin (Dowex 50) as a catalyst (133), with anions such as bicarbonate, phosphate, or chloride at pH 8.0 (134), or with peptide glutaminase at pH 7.0 (135), improved solubiHty, whipabiHty, water binding, and emulsifying properties. 

Copper(I) complexes catalyse a variety of organic reactions which are of synthetic and industrial importance.305 In such processes that involve halide abstraction from aryl or alkyl halides, the abstraction step by a Cu(I) catalyst is believed to be the rate-determining step. In order to circumvent the property of facile disproportionation of Cu, various methods of stabilising Cu(I) and influencing reaction rates were considered.306 A kinetics study of ligand (L) effects on the reactivity of Cu(I)L complexes towards C13CC02 was undertaken. The results indicated that the rate of the chlorine abstraction reaction was affected by several factors. These were the redox potential of the Cu(II/I)L couple, the hybridisation on Cu(I) in the Cu(I)L complex, steric hindrance, and electron density on the central Cu(I) cation at the binding site of the chlorine atom to be abstracted. The volume of activation,... 

We present a method for characterization of the proton affinity distribution (PAD) for binding sites at the oxide/aqueous solution interface. When applied to alumina, a commonly used catalyst support, the results revealed the heterogeneous distribution of acidic/basic surface hydroxyls and possible correlations with their structure. The pH-dependent charging behavior of alumina and the resulting adsorption properties for anions or cations are discussed in relation to the measured proton affinity distribution. Finally, we propose that previous reports on anomolous ion adsorption can be explained on the basis of the existing heterogeneity of proton binding sites at the oxide olution surface. 

A boron bridge offers more functionality than silicon or carbon bridges to the chemistry of group 4 ansa-metallocene complexes because it can reversibly bind a variety of Lewis basic moieties that are designed to influence the electronic and stereochemical properties of the complex. By coordinating an anionic Lewis base, the boron can potentially serve as an internal, counteranion to the catalytically active, cationic group 4 metal alkyl, as in the hypothetical zwitterionic complex shown in Figure 5.1. The polymerization activity of the zwitterionic catalyst should benefit from the remote location of the counteranion from the active site, where it will not compete with the alkene monomer for a coordination site on the metal. 

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