Reaction types, classifications

Finally, oxyallyl cation reactions may not conform strictly to just one of these reaction type classifications. A reaction may be a class A/B reaction proceeding as an asynchronous [4+3] cycloaddition, whereas a class B/C reaction may yield products of both cycloaddition as well as alkylation. 

The first step in an inductive learning process is always to order the observations to group those objects together that have essential features in common and to separate objects that are distinctly different. Thus, in learning from individual reactions we have to classify reactions - we have to define reaction types that encompass a series of reactions with essential common characteristics. Clearly, the definition of what are essential common features is subjective and thus a variety of different classification schemes have been proposed. 

Since 1970 a variety of reaction classification schemes have been developed to allow a more systematic processing of the huge variety of chemical reaction instances (see Chapter III, Section 1 in the Handbook). Reaction classification serves to combine several reaction instances into one reaction type. In this way, the vast number of observed chemical reactions is reduced to a manageable number of reaction types. Apphcation to specific starting materials of the bond and electron changes inherent in such a reaction type then generates a specific reaction instance. 

HORACE used alternating phases of classification (which topological or physicochemical features are required for a reaction type) and generalization (which features are allowed and can be eliminated) to produce a hierarchical classification of a set of reaction instances. 

We will show here the classification procedure with a specific dataset [28]. A reaction center, the addition of a C-H bond to a C=C double bond, was chosen that comprised a variety of different reaction types such as Michael additions, Friedel-Crafts alkylation of aromatic compounds by alkenes, or photochemical reactions. We wanted to see whether these different reaction types can be discerned by this... 

A wider variety of reaction types involving reactions at bonds to oxygen atom bearing functional groups was investigated by the same kind of methodology [30]. Reaction classification is an essential step in knowledge extraction from reaction databases. This topic is discussed in Section 10.3.1 of this book. 

Reaction types can be derived automatically through classification of reaction instances. 

As we have just seen the reaction of alkanes with oxygen to give carbon dioxide and water IS called combustion A more fundamental classification of reaction types places it m the oxidation—reduction category To understand why let s review some principles of oxidation-reduction beginning with the oxidation number (also known as oxidation state)... 

Classification of Reaction Types Design of the Appropriate Bielectrophile... 

Carbanions can take part in most of the main reaction types, e.g. addition, elimination, displacement, rearrangement, etc. They are also involved in reactions, such as oxidation, that do not fit entirely satisfactorily into this classification, and as specific—ad hoc—intermediates in a number of other processes as well. A selection of the reactions in which they participate will now be considered many are of particular synthetic utility, because they result in the formation of carbon-carbon bonds. 

The main principles of pyridine reactivity and how they influence attack at ring atoms have been stated briefly. The most important examples of these reaction types will now be examined in some detail. It will be seen that the principles provide an invaluable, though not infallible, guide to understanding and classification. However, each reaction will have nuances of its own, and some will provide occasional surprises. 

The terms enantio- and diastereoselective reaction, referring to the products of a reaction, are very general terms. A supplementary classification was introduced by Izumi and Tai1 on the basis of the concept of stereotopicity. The Izumi-Tai classification refers strictly to reactants of single-step reactions. This classification uses six reaction types ... 

L. Mattes and S. Farid, in A. Padwa (ed.). Organic Photochemistry, vol. 6, Dekker (1983). The photochemical electron transfer reactions of olefins are described in this account, which provides an interesting perspective that cuts across classifications based on an overall reaction type. 

Table 2 Classification of Reaction Types in Terms of Transfer Free Energies of Reactants, 8GtrR. and Transition State, SGtrTS, and the Resulting Solvent Effect on the Rate of the...

The rationale of classification by reaction types is that different functional groups may show the same kinds of reactions. Thus, as we have just seen, alcohols, carboxylic acids, and amines all can accept a proton from a suitably strong acid. Fortunately, there are very few different types of organic reactions — at least as far as the overall result that they produce. The most important are acid-base, substitution, addition, elimination, and rearrangement reactions. Some examples of these are given below, and you should understand that these are descriptive of the overall chemical change and nothing is implied as to how or why the reaction occurs (also see Section 1-11). 

Fundamental notions and Shilov s classification of conjugated oxidation reaction types. 

I. The study of various types of conjugated reactions and classification of separate cases as belonging to one type or another. 

All of these reactions types can be effected at the cathode or the anode. However, since organic electrode processes often occur via a blend of radical and ionic mechanisms, it should be stressed that the simplicity of the classification scheme above does not imply that the electrochemical oxidation or reduction of a given substrate results in only one type of reaction on the contrary, many processes give products emanating from two or more of the reaction types above, and it may often involve a lot of experimental work to find optimum conditions for a (desired) reaction to occur, if it is at all possible. 

The organization of the review follows the simple scheme that the metals in a group of the periodic table are treated together. A further classification is made by the oxidation states of the involved catalytic species starting with the lowest. The reactions are then further divided by the involved radical reaction types. 

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