Main Classes of Reactions

There are several reviews covering many aspects of nonlinear effects. The early examples of nonlinear effects almost exclusively dealt with organometallic catalysts. It is only very recently that some organocatalysts have been found to 

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Perhaps the synthesis of hydrocarbons is best understood. There are three main classes of reactions leading to complex hydrocarbons carbon insertion, condensation, and radiative association. Carbon insertion reactions are between C+ ions and smaller hydrocarbon neutrals viz.,... 

Alteration of amino acid residues can be obtained by heating at acid or alkaline pH. Main classes of reactions used to chemically modify the side-chain of amino acids are acylation, alkylation, oxidation and reduction (Figure 1). Some of them are described in this chapter. 

Although in catalytic reactions, in particular on the surface of solid catalysts, it is not formally correct to distinguish between acid-base and redox catalysis, because usually they are both involved, this distinction is often common. The two main classes of reactions are selective hydrogenation and selective oxidation. 

Many different kinds of catalytic reactions may lead to a (+)-NLE. Owing to lack of space we will just mention the main classes of reactions without details, more details being available in the review article [1]. 

However, liquid-liquid and solid-liquid systems are the main classes of reactions where PTC finds its most applications, and future discussion and analysis of PTC systems concentrates on LLPTC and SLPTC reactions. 

It is also seen from Table VII that the main classes of reactions of organic catalysis are represented by means of doublet indexes. The classification obtained is close to the classification proposed by Sabatier (i), but is more detailed. Thus, according to Sabatier the reactions of... 

Alkenes can react according to two main classes of reactions (Table 3c) ... 

Enzyme reactions involving methyl groups show none of the stereochemistry associated with prochiral centres as, e.g., the methylene group in ethanol (see above). The hydrogen atoms are indistinguishable (provided they are all one hydrogen isotope, see below) but enzyme-catalysed reactions do occur which involve methyl groups in various ways. Since enzymes are involved the reactions are expected to proceed with a particular stereochemistry. Three main classes of reaction can be identified [14]. By way of illustration we shall briefly examine one of these (Scheme 1.6) (for... 

Comparing the general thermodynamic diagram shown in Figure 1.16 with the four main classes of reactions illustrated in Figure 1.15, we have... 

These reactions are varied in organic- and even inorganic synthesis. The main classes of reactions are summarized in the following scheme (the reaction products are obtained after hydrolysis) ... 

The structural requirements of sulphones to react cathodically and to possess specific electrochemical properties are summarized in Scheme 1. In other words, condition (a) means that aromatic sulphones and a unsaturated sulphones are electroactive, i.e., electron transfer to the LUMO leads to the anion radical, but a cleavage reaction (see b) is mainly observed when R S02 " is a fairly good leaving group. Consequently, the two main classes of electroactive sulphones may react differently with aromatic sulphones, ArS02—R, cleavage is strongly favoured, while with unsaturated sulphones ... 

At this time, although details remain to be elucidated, it seems that most of the main kinds of reactions of disilenes, have been discovered. These have led to numerous new classes of cyclic compounds, some with unprecedented and beautiful structures. In addition, the chemical bonding in disilenes has received serious study and is at least partially understood. 

There are two main classes of [4 + 2 + 2]-metal-catalyzed higher-order cycloadditions that have been reported. The first class involves the reaction of 1,3-dienes (the four-carbon component) with norbornadienes (both two-carbon components) and the second involves the reaction of 1,3-dienes with either two alkynes or an alkyne and an alkene as the two-carbon components (Scheme 59). 

Organometallic compounds are those which contain at least one direct metal-to-carbon bond. The main classes of photochemical reaction of importance to organometallic compounds are given below. 

In Chapter 9, as in most of Unit 4, you learned about equilibrium reactions. In this section, you analyzed precipitation reactions. You mainly examined double-displacement reactions—reactions in which two soluble ionic compounds react to form a precipitate. You used the solubility product constant, Ksp, to predict whether or not a precipitate would form for given concentrations of ions. In Unit 5, you will learn about a class of reactions that will probably be new to you. You will see how these reactions interconvert chemical and electrical energy. 

Various modeling approaches have been used for the catalyst layers, with different degrees of success. The approach taken usually depends on how the other parts of the fuel cell are being modeled and what the overall goal of the model is. Just as with membrane modeling, there are two main classes of models. There are the microscopic models, which include pore-level models as well as more detailed quantum models. The quantum models deal with detailed reaction mechanisms and elementary transfer reactions and transition states. They are beyond the scope of this review and are discussed elsewhere, along with the issues of the nature of the electro catalysts. 

Species (A) and (B) constitute the main class of unsaturated carbenes and play important roles as reactive intermediates due to the very electron-deficient carbon Cl [1]. Once they are coordinated with an electron-rich transition metal, metal vinylidene (C) and allenylidene (D) complexes are formed (Scheme 4.1). Since the first example of mononuclear vinylidene complexes was reported by King and Saran in 1972 [2] and isolated and structurally characterized by Ibers and Kirchner in 1974 [3], transition metal vinylidene and allenylidene complexes have attracted considerable interest because of their role in carbon-heteroatom and carbon-carbon bond-forming reactions as well as alkene and enyne metathesis [4]. Over the last three decades, many reviews [4—18] have been contributed on various aspects of the chemistry of metal vinylidene and allenylidene complexes. A number of theoretical studies have also been carried out [19-43]. However, a review of the theoretical aspects of the metal vinylidene and allenylidene complexes is very limited [44]. This chapter will cover theoretical aspects of metal vinylidene and allenylidene complexes. The following aspects vdll be reviewed ... 

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