Bronstedt-Base

Die zweite Aussage ist dagegen riehtig. Alle drei Anionen besitzen mindestens ein freies Elektronenpaar und konnen daher als Brbnstedt-Base fungieren das Sulfat-Ion ist jedoeh, wie oben erwahnt, nur eine sehr sehwaehe Bronstedt-Base. 

Bimetallic catalysts and multifunctional catalysis, whereby activation of substrate and reactant occurs simultaneously at Lewis acid and Bronstedt base sites, is an approach for giving more organization to the transition state and a higher stereocontrol [125]. 

Figure 8 Productive lactone cleavage with Bronstedt bases (A) and/or additives and final ligand exchange (B).

Reed and co-workers utilized the silylium carboranate salts to generate novel Bronstedt superacids based on carborane anions as conjugate bases by reaction of the salts with liquid HCl [Eq. (7)]. These carborane superacids are able to cleanly protonate Cgo and benzene at room temperature to yield and benzenium... 

It could be shown [5] that the dissolution of polymers depends on the type of ions present in the dissolution medium. Dissolution is base catalyzed and can be described by the Bronstedt dissolution law [38], At a given pH, a linear relationship exists between the logarithm of the dissolution rate and the pKa of the acidic component of the salt present in the dissolution medium. Cellulose acetate phosphate, especially, showed a strong dependency of the dissolution rate on the type of ions added. Sodium chloride prevented the dissolution of some polymers, because the base catalysis was at a minimum level. 

Classical Friedel-Crafts catalysts such as BF3 etherate or Bronstedt acids, which are applied in stoichiometric amounts or even in excess, still have their value, because they are relatively inexpensive yet powerful catalysts for C-H transformation at arenes and, most importantly, they are often successful when modern catalysts fail. Gold(III) chloride, at less than 1 %, has impressive reactivity under very moderate reaction conditions and its selectivity is exceptionally good. Friedel-Crafts type reactions with this catalyst are, however, restricted to very electron-rich arenes. Further studies should concentrate on increasing the electrophilicity of gold catalysts. New catalysts have emerged, for instance based on ruthenium and rhenium, which promise broad applicability based on alternative mechanisms. Catalysts based on rare earth metals are discussed in the next chapter. 

Acid/base catalysis is probably the oldest type of homogenous catalytic reactions. Following the definitions by Bronstedt [6] and Lowry [7], the acids are proton donators and the bases are proton acceptors. Let us consider a bimolecular catalytic reaction with the equation presented as following ... 

Due to the richly hydroxylated surface of MMT, FA was chosen for its ability to compete with hydrogen bonding between platelets, and because it is bio-based. In addition, FA has water-Uke viscosity at room temperature, which facilitates penetration of FA into the interlayer galleries of MMT. The MMT surface contains an abundance of coordinativdy unsaturated Al edge sites which acT as Lewis acids and a surface high in Bronstedt acidity. Because the polymerization of FA to PFA... 

If we consider the more generic Bronstedt s definition of a base and acid, protons and hydroxide ions do not have specific properties in comparison to other bases. For example, with an acid.4H and its conjngated base ", with generic acid-base catalysis, the apparent rate coefficient will have the form ... 

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