A benefit of Fischer projections is that the lowest-priority gro…

A benefit of Fischer projections is that the lowest-priority group can be on the top or bottom of the molecule and still project into the page.

Note: Rotating a Fischer projection in the plane of the page by 90° will also invert the stereochemistry of the molecule. By extension, interchanging any two pairs of substituents will revert the compound back to its original stereochemistry, and rotating a Fischer projection in the plane of the page by 180° will also retain the stereochemistry of the molecule. These manipulations are shown in Figure 2.19.

Note: Chirality can also be thought of as handedness. In fact, one of the easiest visualizations of chirality is to think of your own hands, as shown in Figure 2.9. Although essentially identical, your left hand will not be able to fit into a right-handed glove.

Note: A simple 180° rotation around a vertical axis, as shown in Figure 2.11, allows the compound to be superimposed upon its mirror image.

Note: For example, the C-1 carbon atom in 1-bromo-1-chloroethane has four different substituents. As shown in Figure 2.10, this molecule is chiral because it is not superimposable on its mirror image.

More cards in Chapter 2: Isomers