Synthetic, Kinetic and Thermodynamic Aspects

Synthetic, Kinetic and Thermodynamic Aspects of Reductive Bond Cleavage... 

Synthetic, Kinetic, and Thermodynamic Aspects of Oxidative Bond-formation... 

A very large number of synthetic, as well as many natural, macrocycles have now been studied in considerable depth. A major thrust of many of these studies has been to investigate the unusual properties frequently associated with cyclic ligand complexes. In particular, the investigation of spectral, electrochemical, structural, kinetic, and thermodynamic aspects of macrocyclic complex formation have all received considerable attention. 

A large number of ligand reactions exist where both the kinetic patterns and the general mechanistic features are modified, rather than destroyed, by coordination. These reactions can furnish much information on the way coordination per se will affect the kinetic and thermodynamic aspects of a reaction. Generally, these will be reactions where specific redox properties of the central ion are not involved. In many of these cases coordination can provide a rational basis for the modification of synthetic procedures. 

The synthetic aspects of this acid-catalyzed process have been studied extensively for many years, and they have been reviewed recently by Falbe (1970). The kinetic and thermodynamic details of the various reaction steps in the overall process have been investigated in this laboratory during the last few years with special emphasis on the carbonylation step. The present article reflects the state of affairs in this respect. 

The various aspects, including kinetic and thermodynamic parameters, of this type of reaction have been thoroughly reviewed1 and need not be reiterated here. Only more recent events of potentially wider synthetic utility are included in the following discussion. 

The other application of intensity measurements is in the determination of the relative amounts present of the various components of a mixture. This can be invaluable in kinetic or thermodynamic studies of reactions and this aspect is discussed further in Section 4.17.2. But the value to synthetic chemists lies in the fact that we can study the progress of a reaction in solution, with control of conditions, particularly temperature, and so determine the feasibility of isolating particular components. For example, a base-induced coupling reaction can be used to prepare the unsymmetrical diphosphene (4.IV), by reaction of (2,4,6-Bu 3C6H2)PH2 with (Me3Si)2CHPCl2 [18]. The choice of base and its concentration is critical, and initially the reaction was studied under a variety of conditions by P NMR. Once the optimum conditions had been determined, the way was open to isolation of this new compound. 

The open-framework phosphates, oxalates and other compounds are generally prepared under hydrothermal conditions in the presence of an organic amine which is considered to be a structure-directing agent. There are several intriguing aspects of these materials. Thus, under similar synthetic conditions, one obtains several 3D and other compounds, from the same pot. The use of different amines results in products with differing structures with no obvious relationship, and at the same time, the same amine can also yield compounds of various structures and dimensionalities [8]. While it is recognized that these reactions occur under kinetic control rather than thermodynamic... 

The chemical process of transformation of reactants into products is the subject of studying of chemical kinetics. One can say against it that the chemical reaction is also the subject of studying of several other chemical disciplines, such as synthetic and analytical chemistry, chemical thermodynamics and technolo. Note that each of these disciplines studies the chemical reaction in its certain aspect. In synthetic chemistry, the reaction is considered as a method for preparation of various chemical compounds. Analytical chemistry uses reactions for the identification of chemical compounds. The chemical thermodynamics studies the chemical equilibrium as a source of work and heat, etc. The kinetics also has its specific approach to the chemical reaction. It studies the chemical transformation as a process that occurs in time according to a certain mechanism with regularities characteristic of this process. This definition needs to be decoded. What precisely does the kinetics study in the chemical process ... 

For a synthetic chemist the reaction rate is often the most crucial aspect of kinetics. Synthetic chemistry generally treats reactions in the gas or liquid phase where reactants have high mobilities and where distinct second phases are not normally formed. In semiconductor processing, reaction kinetics such as discussed above is essential to modeling techniques such as chemical vapor deposition (Chapter 12). Solid state chemistry and most materials science of solids is concerned with atomic transport as much as with reactant and product concentrations or thermodynamics. Furthermore, it is often the case that the forward reaction will not occur rapidly until some product is formed. This is normally referred to as a problem of nucleation and is similar to the classic conundrum, which came first, the chicken or the egg In the remainder of this section we will examine nucleation and then turn to diffusion transport kinetics in the following section. 

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