Reactivity and Mechanism

The rate of addition of the nucleophile is influenced by the steric and electronic effects of the two R groups 

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Both the language of valence bond theory and of molecular orbital theory are used in discussing structural effects on reactivity and mechanism. Our intent is to illustrate both approaches to interpretation. A decade has passed since the publication of the Third Edition. That decade has seen significant developments in areas covered by the text. Perhaps most noteworthy has been the application of computational methods to a much wider range of problems of structure and mechanism. We have updated the description of computational methods and have included examples throughout the text of application of computational methods to specific reactions. 

References to the primary literature are provided for specific issues of structure, reactivity, and mechanism. These have been chosen to illustrate the topic of discussion and, of course, cannot be comprehensive. The examples and references chosen do not imply any priority of concept or publication. References to general reviews which can provide a broader coverage of the various topics are usually given. 

Some significant findings concerning the mechanistic details of well-established hydrogenation pathways (e.g., the insertion and reductive-elimination steps) have been published (see Section II), while at the other end of the scale in terms of characterized systems, the enzymatic hydro-genase system is beginning to draw attention (see Section IX). The well-established systems are reviewed first, as new systems are often compared to them in terms of reactivity and mechanism. 

The following discussion of chemical reactivity and mechanism will be based on the premise that for most thermal reactions equilibrium is maintained between water and the micelles, which can be regarded as distinct reaction media, and most kinetic treatments are based on this so-called pseudophase model (Cordes and Gitler, 1973 Bunton, 1973b). Reaction... 

Thioglycosides can also be activated by a one-electron transfer reaction from sulfur to the activating reagent tris-(4-bromophenyl)ammoniumyl hexachloroanti-monate (TBPA+) [102,103]. The use of this promoter was inspired by an earlier report where activation was achieved under electrochemical conditions to give an intermediate S-glycosyl radical cation intermediate [104], and the reactivity and mechanism have also been explored [105,106]. 

Structure, reactivity, and mechanism atom, is very stable ... 

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