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OChem Ch 3.4-4
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Stereoisomers
Identical connectivity but different orientation in space
Cis
Trans
Bond angle strain
E from non-ideal bond angle
E needed for orbitals to distort
Torsional Strain
E
-
repulsion in
neighboring
eclipsed bonds
Transannular Strain
Steric crowding of 2 groups across a ring
Categories of Rings/Strain/Bond Angle
Cyclopropane
Cyclobutane
Cyclopentane
Cyclohexane
Strain free
Chair flip
All axial H become equilateral
All equilateral H become axial
Not a rotation-- Draw a different chair
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.
2 ways to break a bond
Heterolytic Cleavage
Homolytic Cleavage
Heterolytic Cleavage
Homolytic Cleavage
Bond Dissociation Energy (BDE)
Energy required to break a covalent bond via homolytic cleavage
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
2 ways to stabilize radicals
Hyperconjugation
Resonance
Hyperconjugation
Stabilization through donation of e- density from neighboring aligned sp3 C-C/C-H sigma bonds
More hyperconjugation=more stable
Type of induction
Radical Chain Mechanism
1) Initiation
2) Propagation
3) Termination
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Author
Zaqxz
ID
342492
Card Set
OChem Ch 3.4-4
Description
akdlf
Updated
2018-09-23T04:24:21Z
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