Isomerism and Enantiomers Flashcards
lectures 10-13
Lewis structure
Shows the lone pairs of electrons (no lines)
What happens if hybridisation doesn’t occur?
• without hybridisation the molecule will not be tetrahedral
• e.g. The shapes and directions of the C atom valence AOs do not allow for formation of a tetrahedral C atom in CH4
(ref lec.10)
Define constitutional isomers.
• Atoms are connected in a different arrangement
a.k.a structural isomer
What are conformational isomers?
Associated with a specific C-C bond and can be found:
- take molecular model and fixing one carbon, rotate the other carbon
These isomers are conformers (easily distinguished down a c-c bond)
What are the two types of conformers?
- Staggered
* Eclipsed
Staggered vs. Eclipsed conformers
Staggered:
• more stable
• lower in energy
• for long chained alkanes - it is called anti-staggered
Eclipsed (when everything aligns)
• less stable - more steric interactions
• higher in energy
Cycloalkane general formula
CnH2n
What is meant by a sp3 hybridised carbon?
Carbon atom is attached to 4 different groups.
What are the most abundant cycloalkane and why?
- cyclohexane
- 6 membered ring and therefore has no ring strain
- ideal bond angle for sp3 hybridised C atom is 109.5 degrees
What is a ring flip
When 2 chair conformations interconvert which interchanges the axial and equatorial substituents.
Why do equatorial substituents result in a more stable conformation?
There are less steric interactions.
This conformation is also lower in energy (more stable).
Kekule structure
Bonds are shown as dashes (lines)
Fischer model
Shows 3d arrangement by using solid and hashed wedges
Newman projection
shows arrangement directly down a c-c bond (circle wit substituents around it)
What are diastereomers?
Stereoisomers that aren’t enantiomers (ie. not mirror images)
