Conformational Analysis Newman Projections Ring Strain Cyclohexane Conformations
- Slides: 53
Conformational Analysis Newman Projections Ring Strain Cyclohexane Conformations
Views of Ethane
The Newman Projection
Rotational Conformations of Ethane
Definitions • Conformations - Different spatial arrangments that a molecule can adopt due to rotation about sigma bonds. • Staggered - A low energy conformation where the bonds on adjacent atoms bisect each other (60 o dihedral angle), maximizing the separation. • Eclipsed - A high energy conformation where the bonds on adjacent atoms are aligned with each other (0 o dihedral angle).
o 60 Rotation Causes Torsional or Eclipsing Strain
Types of Strain • Steric - Destabilization due to the repulsion between the electron clouds of atoms or groups. Groups try to occupy some common space. • Torsional - Destabilization due to the repulsion between pairs of bonds caused by the electrostatic repulsion of the electrons in the bonds. Groups are eclipsed. • Angle - Destabilisation due to distortion of a bond angle from it's optimum value caused by the electrostatic repulsion of the electrons in the bonds. e. g. cyclopropane
Definitions • Anti - Description given to two substitutents attached to adjacent atoms when their bonds are at 180 o with respect to each other. • Syn - Description given to two substitutents attached to adjacent atoms when their bonds are at 0 o with respect to each other. • Gauche - Description given to two substitutents attached to adjacent atoms when their bonds are at 60 o with respect to each other.
Propane Conformations: Larger Barrier to Rotation (link)
Butane Conformations (C 2 -C 3)
Gauche Interaction in Butane
2 Different Eclipsed Conformations
Strain Energy can be Quantified
Butane has Steric and Torsional Strain When Eclipsed
PE Diagram for Butane (link)
1 -Chloropropane
Saturated Cyclic Compounds
Cyclopropane Angle and Torsional Strain
Electron Density Map
All Dihedral Angles = 0 o
Cyclobutane is not Planar
Cyclopentane
Cyclohexane
Chair Conformation link to active site
Boat Conformation
How to Draw a Chair Conformation all opposite bonds are parrallel
Axial bonds and Equatorial bonds
Rings can Flip from one Chair Conformation to Another
Flipping Chair Conformations • • All axial bonds become equatorial All equatorial bonds become axial All “up” bonds stay up All “down” bonds stay down
Axial-up becomes Equatorial-up
Equatorial Conformation is Preferred (link)
Axial Methyl group is Gauche to C 3 in the ring
Gauche Interactions are Flagged by Parallel H’s 1, 3 -Diaxial Interactions
Equatorial Methyl Group is Anti to C 3 in the ring
cis 1, 3 -Dimethylcyclohexane
trans 1, 3 -Dimethylcyclohexane
cis 1 -Chloro-4 -t-butylcyclohexane
- Cyclopropane newman projection
- Newman projections practice
- Diastereomers vs constitutional isomers
- Conformational isomerism
- Interconvertable
- Drawing chair conformations
- Elastic strain and plastic strain
- Elastic compliance
- 13-c
- Bond angle in cyclohexane
- Condensed structure of cyclohexane
- Consider the disubstituted cyclohexane.
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- Double newman projection
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- Cardinal newman cedar
- Is deciding
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- Newman projection generator
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- Robert c newman ii
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- Richard newman uf
- Scalar projection vs vector projection
- Projection of lines problems with solutions