Chapter 7 Stereochemistry Enantiomers of bromochlorofluoromethane Nonsuperimposable mirror

Chapter 7 - Stereochemistry Enantiomers of bromochlorofluoromethane Non-superimposable mirror images – Enantiomers

Figure 7. 1

7. 12 Optically active molecules of biological importance

$100 billion sales worldwide in 2000 Account for 32% of the $360 billion total drug sales

7. 2 The Chirality Center Carbon atom is asymmetric C is a stereogenic center Enantiomers are stereoisomers since the atoms at the stereogenic carbon are arranged differently in space.

7. 3 Symmetry in achiral structures Mirror images of chlorodifluoromethane are superimposable Figure 7. 2 Achiral i. e. not chiral

7. 4 Optical activity Figure 7. 4 Typical polarimeter setup : [a]D = 100 x (rotation)/(cell length) x (concentration)

7. 8 Enantiomers same physical properties except rotation of plane polarized light one enantiomer positive rotation (+) other negative rotation (-)

Which molecules contain chiral (stereogenic) centers? The stereogenic C must have 4 different groups attached

7. 5 Absolute and Relative Configuration Absolute Configuration – Actual arrangement of substituents in space (+)-2 -butanol and (-)-2 -butanol, but which is which? Relative Configuration - Configuration relative to another compound. Pre-1951, compounds could be related to each other but the absolute configuration was not able to be determined.

7. 6 Nomenclature - Use of the Cahn-Ingold-Prelog System (R) and (S) S enantiomer R - Rectus - the clockwise arrangement of groups S - Sinestre - the counterclockwise arrangement of groups

7. 6 Nomenclature - Use of the Cahn-Ingold-Prelog System

7. 7 Fischer projection formulas Figure 7. 5

7. 9 Reactions that create a Chirality Center Figure 7. 6

7. 10 Chiral molecules with two Chirality Centers Figure 7. 7

7. 10 Representations of (2 R, 3 R)-dihydroxybutanoic acid Figure 7. 8 Conversion of “zig-zag” picture to Fischer projection All the same molecule: (a) and (b) differ only by bond rotation (b) leads to correct Fischer projection

7. 10 Chiral molecules with two Chirality Centers

7. 11 Achiral molecules with two Chirality Centers Figure 7. 9

Meso-2, 3 -butanediol Figure 7. 10

7. 12 Stereogenic centers in cholic acid Figure 7. 11

7. 12 Optically active molecules of biological importance

7. 13 Reactions that produce diastereomers Figure 7. 12

7. 14 Resolution of a chiral substance into its enantiomers Figure 7. 13

Not covering 7. 15 and 7. 16