Potential energy surfaces mechanistic model

Another attempt to perform a general mechanistic consideration of [3 + 21-cycloaddition reactions of nitronates with olefins has been made relatively recently by Prof. Denmark and coworkers (162) using modern quantum-chemical methods, which allow one to correctly calculate the potential energy surfaces for model substrates. Since these data have been summarized in the recent review (335), it is not necessary to consider them as comprehensively as the study in (337). 

This complex and structurally related molecules served as a functional homogeneous model system for commercially used heterogeneous catalysts based on chromium (e.g. Cp2Cr on silica - Union Carbide catalyst). The kinetics of the polymerization have been studied to elucidate mechanistic features of the catalysis and in order to characterize the potential energy surface of the catalytic reaction. 

We begin by briefly reviewing the mechanistic information obtained from the ab-initio MC-SCF computation of the potential energy surface and then illustrate how these results can be rationalized using a VB model. 

Nonetheless, elucidation of the detailed mechanism (e.g., energetics, reaction coordinate, mechanism, potential surface) of the process is not possible with the above qualitative information to elaborate these details, a systematic variation of isotopic composition, energy in the cluster, cluster size, and even solvent, is necessary. Such a study and mechanistic model determination have been carried out (Hineman et al. 1992a) and are discussed below. 

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