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Stereochemistry

Stereochemistry. Unit 8. Stereochemistry. Stereochemistry – the study of compound structures in 3 dimensions Stereoisomers – compounds that differ only in the spatial arrangement of atoms (isomers that differ in how they are connected to eachother). Types of Stereoisomers.

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Stereochemistry

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  1. Stereochemistry Unit 8

  2. Stereochemistry • Stereochemistry – the study of compound structures in 3 dimensions • Stereoisomers – compounds that differ only in the spatial arrangement of atoms (isomers that differ in how they are connected to eachother)

  3. Types of Stereoisomers • Diastereomers – stereoisomers that are not mirror images (like we did in Intro to Hydrocarbons) • Enantiomers – stereoisomers that are mirror images a.k.a. optical stereoisomers

  4. Diastereomers vs.Enantiomers

  5. Simple Enantiomers

  6. Enantiomers • You can have mirror images for any compound • If they are superimposable, they are not stereoisomers • If they are not superimposable, they are stereoisomers and enantiomers

  7. Enantiomers • A compound that has enantiomers is “chiral” and one that has no enantiomers is “achiral” • Chiral = Greek for hand

  8. Enantiomers • To have enantiomers a compound must contain a carbon atom that is bonded to 4 different atoms/groups (asymmetric carbon) • Chiral center (tetrahedral stereocenter) = a carbon atoms that bonds to 4 different atoms/groups

  9. Practice • Ex: CH3CH2CHClCH2CH3 Cl C-C-C-C-C This compound has no chiral centers. Why?

  10. Practice • CH3(CH2)CCHClCH2CH3 Cl Chiral Carbon C-C-C-C-C-C C  bonded to 1. H 3.C-C 2. Cl 4. C-C-C

  11. Practice • Draw the following structures, tell if they do/don’t have a chiral center, and if so, list the 4 diff. groups that bond to the chiral center… • CH3CH2CHBrCH2CH2Cl • 3-ethylhexane • CH2FCH2CHOH(CH2)2CH3 • CH3(CH2)2CClF(CH2)2CHO • CH3CH2CO(CH2)2CH3

  12. Drawing Enantiomers • Cahn-Ingold-Prelog Naming System • We use R and S notation • R= Rectus S=Sinister

  13. Priorities for Drawing Enantiomers • The priorites are an order for atoms that was established by chemists so the structures would be drawn the same

  14. Priority Rules • If all 4 atoms that bond directly to the chiral carbon are different, priority is assigned by atomic number with highest atomic # having highest priority Cl Ex: F-C-H Order? Br

  15. Priority Rules 2. If two or more atoms bonding directly to the chiral center have the same atomic #, look at the atoms they bond to and continue outward until you reach an atom of higher atomic # which makes that group a higher priority Ex: CH3CH2CHCl(CH2)2CH3 Priority for alkyl groups is decyl>9>8>…>1)

  16. Priority Rules 3. A double bond is considered to be bonding to two atoms C=A is considered C-A A A triple bond is considered to be bonding to 3 atoms A C= A is C - A A

  17. Priority Rules #3 example: CH3CH2CHClCHCH2 4. A Real bonding to two atoms takes priority over a double bond / a real bonding to three atoms takes priority over a triple bond EX: (CH3)2CHCHClCHCH2

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