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272_stereo - catastrophe 1 Set priorites based on atomic...

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Chain Chem 272 Stereochemistry Stereochemistry • 3-dimensional aspect encountered when dealing with sp 3 -hybridized carbon A B D C A B D C • When an object cannot be superimposed upon its mirror image, it is chiral • A carbon with 4 diffferent substituents cannot be superimposed on its mirror image • The mirror images are referred to as enantiomers • Enantiomers are spectroscopically identical except for their ability to rotate plane polarized light (i.e. same boiling points, NMR spectra, IR spectra, etc.) O H 3 C CH 3 H O H 3 C CH 3 H Both enantiomers of Carvone • A compound with n stereogenic centers has 2 n possible stereoisomers • Stereoisomers that differ at one or more stereogenic centers that are not enantiomers are termed diastereomers O CH 3 CN Draw all possible stereoisomers of the cyclohexanone given, and indicate their relationship with one another. Assigning Configuration - The Cahn-Ingold-Prelog (CIP) System H 3 C CH 3 HO H OH H 3 C CH 3 H 3 C CH 3 HO H is now and/or
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Unformatted text preview: catastrophe! 1. Set priorites based on atomic number (for isotopes, atomic weight breaks ties (for example hydrogen vs. deutrium - deuterium wins). 2. Nonisotopic ties are broken by looking at the groups attached to the tied atoms. 3. Multiple bonds are treated as multiplied single bonds (for example - treat a carbonyl as two single bonds to oxygen, or an alkene as two single bonds to carbon, see carvone). 4. Now, place the lowest priority substituent back, and if the numbering ascends clockwise, the center has the R configuration. If counter-clockwise, the center has the S configuration. H 3 C CH 3 HO H 1 2 3 4 1 3 2 R R H 3 C CH 3 HO H 1 2 3 4 1 3 2 S S Chiral, Achiral? Assign configurations if chiral (and possible). Challenge: assign configurations to carvone enantiomers OH H 3 C CH 3 CH 3 OH H 3 C CH 3 CH 3 H 3 C H H CH 3 OH H 3 C O CH 3 OH CH 3 Br CH 3...
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