1. Compounds with More Than One Chirality Center
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Chapter 4

2. Drill on Meso Compounds Problem 27
Does the following compound have a stereoisomer that is a meso compound?
No possibility of a plane of symmetry
No meso form
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3. Drill on Meso Compounds Problem 27
Does the following compound have a stereoisomer that is a meso compound?
Plane of symmetry
Meso form possible
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4. Meso Compounds
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5. R,S System for Isomers with More Than One Chirality Center1
If there is more than one chirality center, the R,S system must be applied to each chirality center individually
First determine the configuration at C-2 2 3 4
3-bromo-2-butanol
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6. R,S System for Isomers with More Than One Chirality Center3 2 4 1
3-bromo-2-butanol
C-2 is S
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7. R,S System for Isomers with More Than One Chirality Center
At C-3, consider
interchanging H and Br to get the lowest priority substituent onto a hatched wedge 4 1 2 3
C-3 is R
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8. R,S System for Isomers with More Than One Chirality Center
Compound is (2S,3R)-3-bromo-2-butanol
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9. R,S System for Isomers with More Than One Chirality Center
At C-2, the lowest priority is on a horizontal line
Curve is Clockwise indicating R BUT
Since the H is on a horizontal line R becomes S
C-2 must be S 3
C-2 1 4 2
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10. R,S System for isomers with more than one Chirality Center
At C-3, the lowest priority also is on a horizontal line
Curve is Counterclockwise
Since H is on a horizontal line, S becomes R 2 4 1
C-3 3
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11. R,S System for isomers with more than one Chirality Center
Compound is (2S,3R)-3-bromo-2-butanol
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Chapter 4

12. Stereoisomers of Tartaric Acid
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Chapter 4

13. Regioselective, Stereoselective, and Stereospecific Reactions
A regioselective reaction is one in which two or more constitutional isomers are possible, but more of one than the other is obtained
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14. Regioselective, Stereoselective, and Stereospecific Reactions
A stereoselective reaction is one in which two or more stereoisomers are possible, but more of one is obtained than the other
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15. Regioselective, Stereoselective, and Stereospecific Reactions
A stereospecific reaction is one in which a stereoisomeric reactant produces only one specific stereoisomeric product; the other stereoisomer of the reactant produces a different stereoisomeric product
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16. Stereochemistry of Alkene Addition Reactions
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17. Stereochemistry of Alkene Addition Reactions
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18. Addition Reactions that Form Two Chirality Centers
For reactions that proceed through a carbocation or radical intermediate, the electrophile first attacks the double bond from either side, yielding both enantiomers of a carbocation with one chirality center
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19. Addition Reactions that Form Two Chirality Centers
The nucleophile then can attack the racemic carbocation from either side, yielding four possible stereoisomers
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20. Syn Addition When the two substituents add to the same side
Addition of H2 is a syn addition
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21. Anti Addition When the two substituents add to opposite sides
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