 However, when a CLA is used in the same reaction, the energetic barrier of formation of one diastereomer is less than that of another – the reaction is under kinetic control.If the difference in the energy barriers between the diastereomeric transition states are of sufficient magnitude, then a high enantiomeric excess of one isomer should be observed (Figure 2).Diels-Alder reactions occur between a conjugated diene and an alkene (commonly known as the dienophile).