Planes, 97, illus

The main features in the conformational analysis of these compounds, i.e. relative stabilities of syn and anti conformers, rotation energy barriers and eventually out of plane distortions of the anti conformers, result in manyfold weak interactions and it would be tedious and illusive to give their complete qualitative analysis. We can nevertheless display the most important of them and indicate the trends induced by the change of the nature of the substrate (enol or thioenol) or the position and the nature of substituents. Two interactions seems to be effective enough to be taken into account electrostatic repulsions and attractions, and ir orbital effects. 

Rhythm is the term used to describe the illusion of flow or movement created by having a regularly repeated pattern of Lines, planes, or surface treatments. 

Advancing colors n. Colors that give the illusion of being closer to the eye than their complementary colors when both are adjacent and in the same plane colors ranging from yellow-green to scarlet are examples. 

In Figure 2.11, a trajectory appears to cross itself. This is an illusion caused by our efforts to portray a higher dimensional system in two dimensions. A trajectory cannot cross itself because solutions to the sorts of ordinary differential equations that occur in chemical kinetics are unique. If a trajectory seems to cross itself in two dimensions, then the system actually has higher dimension (it is not completely determined by two variables). A two-variable plot projects the higher dimensional trajectory onto a plane, giving the appearance of a crossing of the trajectory. Figure 2.11b shows a two-dimensional projection of a three-... 

We can also look for planes of symmetry in nature. The fern frond shown in Figure 1.3 looks perfectly normal at first glance. However, on close inspection it can be seen that the left side of the leaf is just a reflection of the right-hand side on the surface of a pond. The picture is shown with the water surface vertical, which enhances the illusion. From half the leaf and its reflected image we can easily imagine the complete structure. 

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