absolute - 2.-or- use the Hand Rule. Orient the lowest...

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Assigning the Configuration 1. Use the Cahn-Ingold-Prelog Rules to assign priority to the four group. Orient the molecule so that the lowest priority group is in the back (away from you). 2. Look at the remaining three groups of priority 1-2-3. If the remaining three groups are arranged so that numbering the priorities 1-2-3 are in a clockwise fashion, then assign the stereogenic center as R (“r ectus” or right). If the remaining three groups are arranged 1-2-3 in a counterclockwise manner, then assign the stereogenic center S (“s inister” or left). OH H CH 3 CO 2 H orient lowest priority group away OH H 3 C CO 2 H H 1 2 3 4 1 2 3 clockwise = R OH H CO 2 H CH 3 orient lowest priority group away OH HO 2 C CH 3 H 1 3 2 4 1 3 2 counter clockwise = S
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Unformatted text preview: 2.-or- use the Hand Rule. Orient the lowest priority group up. Point your thumb in the direction of the lowest priority group. If you need to use your right hand so that your fingers point in the direction of the group priorities in the order 1-2-3, then the stereogenic center is assigned R (r ectus or right ). If your left hand is required so that your fingers point in the direction of the group priorities 1-2-3, the the stereogenic center is assigned S (s inister or left ). (S)-(+)-Lactic acid (Left Hand) (R)-(-)-Lactic acid (Right Hand) H HO 2 C CH 3 OH 4 2 3 1 H CO 2 H H 3 C HO 4 2 3 1...
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This note was uploaded on 03/11/2012 for the course CHEM 220A taught by Professor Sulikowski during the Fall '08 term at Vanderbilt.

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