As can be seen from the graph, pyramidalization increases
as the double bond is progressively twisted. As a result of
pyramidalization, even at very large twist angles, most of the
strength of the π bond (i.e., orbital overlap) is retained. Note
that in Figure 4 each of the two drawings shows a dihedral
angle between the allylic carbon atoms of 135. However, the
orbital overlap in the pyramidalized structure (right) is much
larger than in the unpyramidalized structure (left).