OChem Ch 3.4-4

  1. Stereoisomers
    Identical connectivity but different orientation in space
  2. Cis

    Trans
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  3. Bond angle strain
    • E from non-ideal bond angle
    • E needed for orbitals to distort

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  4. Torsional Strain
    Erepulsion in neighboring eclipsed bonds

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  5. Transannular Strain
    Steric crowding of 2 groups across a ring

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  6. Categories of Rings/Strain/Bond Angle
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  7. Cyclopropane
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  8. Cyclobutane
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  9. Cyclopentane
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  10. Cyclohexane
    • Strain free
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  11. Chair flip
    • All axial H become equilateral
    • All equilateral H become axial
    • Not a rotation-- Draw a different chair

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  12. What does equilibrium favor in terms of chair conformations?
    It favors the chair with the most and larges groups equatorial. The equatorial conformation is favored by a ratio of 95:5.

    • 1,3-diaxial interactions is a type of transannular strain.
    • Groups 1,3 are in the same axial plane and interact sterically with a larger molecule.
    • There is also gauche interactions for each axial group.
  13. 2 ways to break a bond
    • Heterolytic Cleavage
    • Homolytic Cleavage
  14. Heterolytic Cleavage
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  15. Homolytic Cleavage
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  16. Bond Dissociation Energy (BDE)
    Energy required to break a covalent bond via homolytic cleavage
  17. Bond Strength Factors
    • 1) Stronger bonds form between overlapping orbitals of the same size
    • 2) Stronger bonds create less stable radicals
    • 3) Stronger bonds are harder to break

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  18. 2 ways to stabilize radicals
    • Hyperconjugation
    • Resonance
  19. Hyperconjugation
    Stabilization through donation of e- density from neighboring aligned sp3 C-C/C-H sigma bonds

    • More hyperconjugation=more stable
    • Type of induction

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  20. Radical Chain Mechanism
    • 1) Initiation
    • 2) Propagation
    • 3) TerminationImage Upload 15
Author
Zaqxz
ID
342492
Card Set
OChem Ch 3.4-4
Description
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Updated