Homogeneous reactions rate-determining path

The interaction of a prochiral molecule with a chiral homogeneous catalyst results in the formation of diastereomeric intermediates and transition states. High enantioselectivity is obtained if for the rate-determining step out of the many possible diastereomeric transition states, one is energetically favored. In such a situation the reaction follows mainly this path. Other possible pathways that cause dilution of optical purity are avoided. A fundamental point to note is that diastereomers, unlike enantiomers, need not have identical energies. The presence of a C2 axis of symmetry in these ligands makes some of the possible diastereomeric transition states structurally and energetically equivalent. As the... 

Here, too, only one straight-line reaction path can be found, namely, that for initial mixtures containing the isomers Ai and A2 in their steady-state ratio [i.e., as homogeneous source as defined in Section 5.3). This mixture is a pseudo-component. Unless isomerization is very fast compared with conversion, there is no unique equilibrium point because the relative amounts of P and Q at complete conversion depend on the initial isomer distribution. The single straight-line path and the rate of progress along that path are insufficient for determination of the four non-zero rate coefficients of the network. 

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