Bronsted base inorganic bases

Such observations lead to the designation of reactions as acid- or base-catalyzed. When the catalysis is limited to the species H+ (or OH ), the reaction is spoken of as being subject to specific ion (or OH ion) catalysis. Many reactions of both organic and inorganic chemistry fit such a designation. However, very early work on such systems soon showed that the catalysis was not limited to or OH but did extend to other species which could be subsumed under the category of what are now called Bronsted acids and bases. 

The mechanism operating in enantioselective Michael reactions under PTC conditions involves the formation of a chiral ion-pair between the nucleophile and the catalyst as the key phenomenon operating in the stereocontrolled formation of the new stereogenic center. The reaction typically incorporates an acidic pro-nucleophile (in almost all cases an enolizable carbonyl compound), the Michael acceptor, the catalyst and a Bronsted base, which is typically an inorganic salt such as a hydroxide or a carbonate (Figure 5.1). It starts with the... 

These other concepts of acids and bases are not so easily applied quantitatively as the Lowry-Bronsted concept. Nevertheless they have proved to be very useful as ways of classifying chemical substances and—more importantly— these ideas have been a stimulus to many advances in inorganic chemistry. 

Cas/liquid reaction 28 [CL 28] Acid-base reaction between ammonia and Bronsted inorganic acids... 

Although the discussion to this point has been concerned with the explanation of the behavior of Bronsted acids as catalysts, there is an enormous range of reactions in which catalysis by acids and bases occurs. Many of the important types of organic reactions involve catalysis by acids or bases. In this section, several reactions will be mentioned, but the mechanistic details will not be presented in this book on inorganic chemistry. The discussion is intended to show the scope of catalysis by acids and bases. 

Many mechanisms in organic chemistry start with an acid/base reaction. This may be just a simple Bronsted-Lowry protonation of a hydroxyl group, which results in the activation of a C-OH bond or it may be a Lewis acid/base reaction as, for example, when aluminium trichloride complexes with a halogenoalkane in the first step of the Friedel-Crafts reaction. In each case, the initial intermediate usually reacts further and leads to the desired product. In inorganic chemistry, the acid/base reaction may be all that is of interest, e.g. the treatment of a carbonate with an acid to liberate carbon dioxide. However, it is unusual in organic chemistry for the acid/base reaction to be an end in itself. It is for this reason that acid/base characteristics are normally considered as a property of the molecule, similar to the nucleophilic and electrophilic properties to which they are closely related, rather than as a fundamental reaction type as is the case in inorganic chemistry. 

Drummond et al. [54] synthesized protic ionic liquids by combining Bronsted acid/base pairs where the primary amine cations were of the form RNH3 and R(OH) NH3 combined with organic anions of the form RCOO, R(OH)COO or with an inorganic anion. They studied physicochemical properties of synthesized PILs at nominally equimolar ratio of anion and cation (1 1 stoichiometry) and in the presence... 

Many organic compounds can act as weak Bronsted-Lowry acids or bases. Their reactions involve the transfer of H+ ions, or protons (Section 10-4). Like similar reactions of inorganic compounds, these acid-base reactions of organic acids and bases are usually fast and reversible. Consequently, we can discuss the acidic or basic properties of organic compounds in terms of equilibrium constants (Section 18-4). 

The use of homogeneous Bronsted and Lewis acids and bases was one of the main reasons for the production of high amounts of inorganic salts as byproducts in industrial syntheses. The ratio of mass unit by-product per mass unit of product is explained as an E-factor by Sheldon for several industry segments. For example, in the fine chemical industry and for the production of pharmaceuticals, sometimes 50-150 kg of by-products per kg desired product are formed. Therefore, new processes in the production of fine chemicals in order to reduce the high numbers of by-product formation are needed. 

The importanee of aeid-base interactions in various fields of ehemistry led to extensive research in the 1960s to obtain acid-base scales. This resulted in the Hard and Soft Aeids and Bases (HSAB) seales of Pearson [30], Drago s E and C eonstants [31], and Gutmann s donor and aeeeptor numbers [32]. Bolger and Miehaels [33] have used Bronsted acid base ehemistry to predict the adhesion of organie and inorganic species. 

In the case of organic inorganic materials interaction (e.g., polymer-metal oxide), Bolger and Michaels [33] suggested a model based on Bronsted acid-base chemistry to account for the strength of the interaction. They defined a parameter A for organic adds and bases ... 

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