Mechanistic nomenclature

The situation is quite different when the nucleophile acting as the catalyst is present in relatively small concentration (as compared to the solvent), since the kinetic order with respect to the nucleophile can, in principle, then be obtained. The mechanistic nomenclature can then be modified so as to include mention of the nucleophilic catalyst. 

After some discussion, the Ingold system of mechanistic nomenclature (Al, [Pg.758]

The lUPAC recommendations for oral and written naming of organic reaction mechanisms (lUPAC 1989 a) are intended to replace the mechanistic nomenclature devised by Ingold (1953, 1969). Ingold developed his method in the 1930 s, i. e. at a time when relatively few mechanisms were unambiguously known. In the following decades several new mechanisms and variants were established making the applica-... 

In view of this background, it is the aim of this chapter to organize the fundamentals of radical additions to 1,2-dienes and to present its state of the art in organic synthesis. All aspects of enyne allene cyclizations [19, 20] have been omitted since this topic is addressed in Chapter 20. In order to simplify the mechanistic discussion, the positions and Jt-bonds of allenes have been consistently numbered using the nomenclature outlined in Figure 11.1. 

First, we will refer to the direct use of hydrocarbon fuels in an SOFC as direct utilization rather than direct oxidation. Second, we recognize that the broadest definition of direct utilization, exclusive from mechanistic considerations, should include rather conventional use of fuel by internal reforming, with steam being cofed to the fuel cell with the hydrocarbon. Indeed, this nomenclature has been used for many years with molten-carbonate fuel cells. However, because internal reforming is essentially limited to methane and because the addition of steam with the fuel adds significant system complexity, we will focus primarily on systems and materials in which the hydrocarbons are fed to the fuel cell directly without significant amounts of water or oxygen. 

Base hydrolysis of amides also requires quite vigorous conditions, but mechanistically it is exactly equivalent to base hydrolysis of esters. After nucleophilic attack of hydroxide on to the carbonyl, the tetrahedral anionic intermediate is able to lose either an amide anion (care with nomenclature here, the amide anion is quite different from the amide molecule) or hydroxide. Although loss of hydroxide is preferred, since the amide anion is a stronger base than hydroxide, this would merely reverse the reaction. 

Nitrenium ions (or imidonium ions in the contemporaneous nomenclature) were described in a 1964 review of nitrene chemistry by Abramovitch and Davis. A later review by Lansbury in 1970 focused primarily on vinylidine nitrenium ions. Gassmann s ° 1970 review was particularly influential in that it described the application of detailed mechanistic methods to the question of the formation of nitrenium ions as discrete intermediates. McClelland" reviewed kinetic and lifetime properties of nitrenium ions, with a particular emphasis on those studied by laser flash photolysis (LFP). The role of singlet and triplet states in the reactions of nitrenium ions was reviewed in 1999. Photochemical routes to nitrenium ions were discussed in a 2000 review. Finally, a noteworthy review of arylnitrenium ion chemistry by Novak and Rajagopal " has recently appeared. 

Hydrolysis and condensation reactions of silanes may be considered in the broad category of nucleophilic substitutions at silicon. The common nomenclature for these reactions is SN.V-Si, where A represents the kinetic order or molecularity, Si indicates that silicon is the reaction center, and SN indicates that the reaction is a nucleophilic substitution. Nucleophilic reactions at silicon have been reviewed thoroughly and have been the subject of fundamental studies by several laboratories over the last three decades [33]. The literature is not as voluminous as the literature on the corresponding reactions at carbon. A general mechanistic view of these reactions has, however, emerged. There are many parallels to carbon-centered reaction mechanisms. One distinction from carbon-centered reactions is clearly apparent. Silicon is able to form relatively stable higher coordinated (pentavalent) intermediates carbon is not [33]. 

Even now, there are two further limiting cases, for if k equilibrium constant for complex formation. Experimentally it will be a matter of extreme difficulty to distinguish either of these possibilities from mechanism SE2(open) or SE2 (cyclic), since all of these mechanisms require the reaction to follow second-order kinetics. Indeed, Reutov4 appears to include a situation such as (7), if the complex is present but in very low concentration, under the mechanistic title of SE2. This is also the nomenclature used by Traylor and co-workers11, but Abraham and Hill5 refer to such a situation as SEC (substitution, electrophilic, via co-ordination). 

Secondly, a mechanistic classification scheme is necessary to narrow down a vast and ill-defined subject matter to a manageable size with a consistent content. Moreover, we will here have to take the first steps in transferring inorganic concepts into organic ones. Whatever we may think of nomenclature and definitions, science would not exist without them. 

I devoted a significant effort in the next chapter to nanomaterials, due to their increasing popularity and relevance for current/future applications. In addition to structure/property descriptions and applications, essential topics such as nomenclature, synthetic techniques, and mechanistic theories are described in detail. The last chapter is also of paramount importance for the materials community -characterization. From electron microscopy to surface analysis techniques, and everything in between, this chapter provides a thorough description of modern techniques used to characterize materials. A flowchart is provided at the end of the chapter that will assist the materials scientist in choosing the most suitable technique(s) to characterize a particular material. 

Mechanistic possibilities for phosphoryl transfer 51 Nomenclature issues 53... 

The terminology and classification of fault-rocks and seal types is not yet universally agreed (Knipe, 1992a Knott, 1993). The classification presented below is based on identification of the main process responsible for the reduction in permeability associated with the faults. Mechanistic terms have been combined with textural descriptive terms to provide a more expansive nomenclature system which covers the most common fault rocks and seat types. The fault seal types and associated fault-rock types can be divided into two broad categories ... 

Two extreme mechanistic possibilities arise for the substitution of a water ligand in [M(H20) ]m+ by L and are conveniently discussed using the nomenclature of Langford and Gray.220 The first occurs when [M(H20) ]m+ and L pass through a first transition state to form a reactive intermediate, [M(H20)raL](m x)+, in which the coordination number of Mm+ is increased by one (Equation (7)) ... 

Voltammetric methods provide ways to study mechanistically complex electrode reactions in which chemical reactions accompany the electron transfer. Chemical reactions can be coupled to electron transfer, either preceding or following it. A nomenclature that aids in cataloging coupled chemical reactions denotes E as an electron-transfer step and C a chemical reaction. Thus, EC refers to a chemical reaction following electron transfer. Even a simple mechanism, such as CE, can be complex owing to such variables as the reversibility of E, the rate and equilibrium constants of C and the time scale of the electrochemical experiment. Our discussion is restricted to the limiting kinetic cases for each mechanism. 

Because of the higher priority give to sulfur, the Z monothioketene acetal derived from the corresponding monothioester is mechanistically equivalent to the ketene acetal derived from an ester. Care must be taken when comparing the results from monothioketene acetals with the results from ketene acetals to avoid confusion as a result of the nomenclature inversion. 

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