1. CH 5-5: Fisher Projections - Viewing stereoisomers with 2 or more Chiral Centers
Maximum Stereoisomers for 2,3-dibromobutane?
(2S,3R)
(2R,3R)
(2R,3S)
(2S,3S)

2. Drawing a Fisher Projection
1. Draw a “double cross” (one cross for each chiral center) R
2. Horizontal bonds are “forward”, the top and bottom “vertical” bonds are “back” R
3. Assign configurations in the usual way
4. The entire Fisher Projection can be “rotated” in the plane of your paper, but not “flipped” out of the plane
5. Any chiral carbon can be rotated, but all atoms or groups must be rotated in unison (equivalent to C-C bond rotation)

3. Draw the Fisher Projections for all 2,3-dibromobutane stereoisomers:
(2R,3R)
(2S,3S)
(2R,3S)
(2S,3R)
Are any of these stereoisomers superimposable?