In This Chapter
Seeing molecules in three dimensions
Determining R and S stereochemistry
Shedding (plane-polarized) light on chiral molecules
Discovering diastereomers and Fischer projections
In this chapter, you look closely at molecules in three dimensions. Why should you care about the arrangements of atoms in three-dimensional space? Because nature does. Virtually all the compounds produced in nature — proteins, sugars, carbohydrates, DNA, and RNA, to name just a few — have atoms oriented in very specific ways in three-dimensional space.
Subtle differences in the way molecules are arranged in three-dimensions can be recognized, for instance, by your nose receptors. Limonene, for example, shown in Figure 6-1, can have two different three-dimensional configurations (solid wedges indicate a bond coming out of the plane of the paper; dashes indicate a bond going back into the paper). If the molecule is arranged in one configuration, it smells of oranges; arranged in the other configuration, it smells of lemons!