General Topics by Reaction Type

We have classified the many reviews dealing with these materials under the following headings  

Structure and Stereochemistry (it is self-subdivided into Theoretical Aspects, Stereochemical Aspects, Betaines and Other Unusual Structures, Miscellaneous Substituted Heterocycles). 

Reactivity (General Topics Reactions with Electrophiles and Oxidants, Reactions with Nucleophiles and Reducing Agents, Reactions Toward Free Radicals, Carbenes, etc.. Reactions with Cyclic Transition State, Reactivity cf Substituents, Heterocycles as Intermediates in Organic Synthesis). 

Syntheses ((General Topics and Nonconventional Synthetic Methodologies, Synthetic Strategies and Individual Methods, Versatile Synthons and Specific 

Reagents, Ring Synthesis from Nonheterocyclic Compounds, Syntheses by Transformation of Heterocycles). 

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B. General Topics by Reaction Type 1. Structure and Stereochemistry... 

General Topics by Reaction Type 2.2. / General Sources and Topics... 

The rates of chemical processes and their variation with conditions have been studied for many years, usually for the purpose of determining reaction mechanisms. Thus, the subject of chemical kinetics is a very extensive and important part of chemistry as a whole, and has acquired an enormous literature. Despite the number of books and reviews, in many cases it is by no means easy to find the required information on specific reactions or types of reaction or on more general topics in the field. It is the purpose of this series to provide a background reference work, which will enable such information to be obtained either directly, or from the original papers or reviews quoted. 

There is one important difference between the case of an isomeric reaction and a more general one of the type (9). In any nonisomeric reaction there is an essential chemical difference between the reactants and the products of chemical reaction. It is possible that one of the reactants or one of the products will be strongly adsorbed on the surface. Since they differ chemically it is not necessary that both reactants and products be adsorbed equally, as in the case of an isomeric reaction. Should one of the reaction products be adsorbed strongly, the reaction may be blocked because the active regions become sheathed with an obstructing layer. On the other hand, the reaction need not be blocked if one of the reactants is strongly adsorbed since the reaction itself will tend to remove this obstruction. This topic has been made the subject of detailed discussion by Frankenburg (2). 

In this chapter several general topics important to understanding acid-base systems are considered and then illustrated by acid-base reactions in three typical solvent types. Finally, pH measurements in solvent mixtures and the Hammett acidity function are discussed. 

In principal, two types of related substances or impurities must be considered and are discussed here separately reaction byproducts present as a result of the synthesis and the production process (Ch. 9.5.2), and degradation products of the active drag substance in a formulation (Ch. 9.5.3). These sections on selected examples are preceded by a discussion on general topics related to the search for impurities by LC-MS (Ch. 9.5.1). Finally, LC-MS controlled fractionation in preparative LC is discussed (Ch. 9.5.4). 

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