Kinetic product distribution anticipating

This chapter provides examples showing how molecular modeling can be used not only to rationalize observed product distributions in kinetically-controlled reactions, but also to anticipate and ultimately control the distribution of products. 

This paradigm, anticipating kinetic preferences by examining thermodynamic preferences in analogues, offers a powerful means to explore product distributions in kinetically-controlled reactions. 

Organic chemists have a variety of strategies which they can pursue in order to improve product selectivity. Some of these like temperature and reaction time rest on the balance between thermodynamic and kinetic reaction pathways (see discussion in Chapter 1). Others such as solvent and external additives (catalysts) may as well lead to changes in the relative stabilities of competing transition states. Because it has been so widely explored, Diels-Alder chemistry provides a good opportunity to examine these variables and, in addition, to survey the use of calculations in anticipating changes in product distributions. 

Under intrinsic-kinetic conditions the carbon number distribution of products from a reduced fused magnetite catalyst Is not significantly affected by wide variations In H, and CO concentration and mass-transfer resistances have no noticeable effect, as would be expected. To the extent that other selectlvltles, such as oxygenate product composition, are governed by H and CO concentrations In the liquid, we would similarly expect to observe effects caused by mass transfer, although this was not done here. Likewise with other catalysts, such as cobalt, which appear to be more sensitive to reaction conditions and to secondary reactions, more marked effects from significant mass transfer reactions are anticipated. 

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