Reaction in Presence of Water
An alternative classification with broader scope is suggested by Yujiro Hayashi as he describes certain organocatalytic Aldol reactions as taking place in the presence of water. The observed effect in these reactions is not rate acceleration (that would be On Water) but happens to be increase in enantioselectivity.
In the context of organocatalysis both concepts of on-water reactions and in-the-presence-of-water reactions have been criticized in 2007 as not so environmentally friendly by Donna Blackmond. According to Blackmond, separation of reaction product from the water phase usually requires organic solvent anyway and in reported aqueous systems the water phase can in reality be less than 10% of the total reaction mixture with another component forming the actual solvent. Blackmond also notes that in reported instances, the observed rate-acceleration in presence of water is in fact due to water suppressing reaction deactivation.
Read more about this topic: On Water Reaction
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