Chapter 3: 3.3 Drawing Organic Compounds in 3D Flashcards
List:
The ways to respresent molecules in 3D
- Wedge/dash formula
- Newman projections
- Fischer projections
Describe:
Wedge/Dash Formula
Uses 3 kinds of lines:
1. Straight lines are in the plane of the page
2. Wedges are out of the plane of the page
3. Dashes are behind the plane of the page
Describe:
Newman Projections
Looks down the axis of a bond (usually a carbon-carbon bond in an alkane)
* Places the substituents around those atoms which are connected to the axis in a position that allows us to understand their overlap
Describe:
Fischer Projections
A good way to see two adjacent chiral centers
* Horizontal arms are coming out of the plane (wedges)
* Vertical arms are going into the plane (dashes)
What is the purpose of a Wedge/Dash Notation?
Specifies whether bonds are going into the page or out of the page
What is the purpose of a Newman projection?
To visulaize conformational changes by looking “down” a C-C bond
What is the purpose of Fischer Projections?
Commonly used in determining stereochemistry (substituents can be easily moved around to compare stereochemistry)
Define:
Conformational Isomers
Have the same molecular formula and bond connectivity but are isomers by bond rotation
What are the most common forms of conformational isomers in organic chemistry?
Alkanes
How are conformational isomers usually represented?
Newman Projections or Fischer Projections
True or False:
Conformational isomers are different molecules
False, the are the same molecule with the rotation around a single bond (never present when there is a pi bond)
What does “conformers” mean?
Conformational isomers
Why are different conformers favoured?
Due to steric interactions, certain conformers are favoured for enthalpic reasons
What are the main conformations?
- Staggered
- Eclipsed
What are the ways the functional groups can be orientated in staggered conformation?
- Anti (largest functional groups opposite to each other)
- Gauche (largest functional groups staggered)
