page_title: Non-linear effects
section_title: Interpretation of the ML3 Model
hierarchical_section_title: Non-linear effects / Modeling non-linear effects / ML3 model / Interpretation of the ML3 Model
caption_attribution_description: English: In the case where the heterochiral complexes are less reactive and selective than the homochiral complexes.
context_page_description: In enantioselective synthesis, a non-linear effect refers to a process in which the enantiopurity of the catalyst or chiral auxiliary does not correspond with the enantiopurity of the product produced. For example: a racemic catalyst would be expected to convert a prochiral substrate into a racemic product, but this is not always the case and a chirally enriched product can be produced instead.
  This can be expressed mathematically, as shown in Equation 1. Stereoselection that is higher or lower than the enantiomeric excess of the catalyst is considered non-ideal behavior. In non-ideal behavior, this deviation from linearity is described as the non-linear effect, NLE.
  For an ideal asymmetric reaction, the eeproduct may be described as the product of eeₘₐₓ multiplied by the eecatalyst. This is not the case for reactions exhibiting NLE's.
  Non-linear effects often arise in reactions with a scalemic catalyst composition. As first observed by Wynberg and Feringa in 1976, different enantiomers of the chiral catalysts form heterochiral complexes, more specifically high order aggregates or dimeric forms of the catalyst.
context_section_description: In general, interpreting the correction parameter values of g to predict positive and negative non-linear effects is considerably more difficult. In the case where the heterochiral complexes MLRLRLS and MLSLSLR are less reactive than the homochiral complexes MLSLSLS and MLRLRLR, a kinetic behavior similar to the ML₂ model is observed (Figure 9). However, a substantially different behavior is observed in the case where the heterochiral complexes are more reactive than the homochiral complexes.
caption: Figure 10: When the homochiral complexes are more selective and reactive than the heterochiral complexes.[4]
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