The energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital is important in controlling reaction rate in this type of reaction.  
The energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital is important in controlling reaction rate in this type of reaction.  The reaction has a stereochemical feature resulting in two possible orientations, with the endo adduct preferentially formed when the reaction is under kinetic control.  An example of this reaction is the combination of acrylonitrile and 1,3-butadiene.  Utilizing the compound cyclopentadiene to make cyclohexanes, it earned its discoverers the 1950 Nobel Prize in chemistry.  FTP, name this reaction named for two Germans.
The energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital is important in controlling reaction rate in this type of reaction.  
Diels-Alder reaction