Carbons in the Molecule: Count the total number of carbons; six carbons mean you can choose six different bonds from different orientations.
Indicate Front and Back Carbons: When drawing a Newman projection, identify which carbon is in the front and which is in the back.
It’s important for visualizing what groups are attached to each carbon.
Hints for Drawing:
Include hydrogen atoms explicitly using wedges (for groups coming toward you) and dashes (for groups going away).
You can abbreviate methyl groups as ME (CH₃) and ethyl groups as ET (C₂H₅) to simplify.
Skeletal structures are acceptable as long as they represent the correct number of carbons.
Perspective: Look down the bond you’re representing, considering the orientations of groups coming off the front and back carbons.
Consider conventional versus unconventional positions; choose the correct projection template for a valid representation.
Staggered Conformation:
Lower energy due to the spread of atoms, making it more stable.
Eclipsed Conformation:
Higher energy due to overlapping atoms; geometric rotations can lead to different conformations.
Chair Conformations:
Cyclohexane is commonly represented as a hexagon but in reality, it’s three-dimensional.
Wedges and dashes help indicate how groups are situated in space (up or down).
Directional Information:
Groups represented on dashes are positioned away from you and those on wedges are positioned towards you.
Types of Chair Conformations:
Axial Lines: Alternating up and down for adjacent carbons.
Equatorial Lines: Positioned more horizontally, giving a different perspective and potential energy state.
Energy Diagrams: Understanding potential energy in different conformations is essential.
Stability Factors: Different arrangements can lead to steric strain when atoms or groups are too close, particularly when substituents occupy axial positions.
Chair Flip: A process of transitioning from one chair conformation to another, where axial groups switch to equatorial positions and vice versa.
Practice Drawing the Chair: Focus first on axial lines and then equatorial lines.
Visual mnemonic: Think of axial lines as chimneys on a house; they should not point inside the house.
Stability is achieved by keeping larger substituents in equatorial positions to minimize steric strain.
Common Mistakes:
Ensure not to position two axial or two equatorial groups on a single carbon; each must alternate.
Check for equatorial lines' correct directional placement based on their carbon's position (left/right).