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Unformatted text preview: you absolute configuration Naming Enantiomers Cahn-Ingold-Prelog R,S-Nomenclature
Label all substituents at stereocenter, starting at point of attachment, according to the sequence rules in order of decreasing priority: a, b, c, d (note color scheme). Look down C-d bond: a, b, c clockwise : R
c a C
b a, b, c counterclockwise : S R d Cahn-Ingold-Prelog
1966 Sequence Rules
1. Order by atomic number, i.e. H = 1, lowest. Hd a I 2. If same priority at first atom: Go to first difference. Br b C R * c CH3 Exception: lone pair, # "zero". E.g., amines:
point of N : d -CH2CH3 < -CH2CH2SH -CCH3 H CH3 CH3 < -CH2CH2SCH3 -CH2CH2OH < -CHCH3 -CH2CBr3 < D -CHCH3 3. Multiple bonds: Add double or triple representations of atoms at the respective other end of the multiple bond. H C C H H H C C C C C C C C C C C C N C C N C N...
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This note was uploaded on 03/21/2012 for the course CHEM 140A taught by Professor Whiteshell during the Fall '04 term at UCSD.
- Fall '04