L18 - Aromacticity 1 Flashcards
1
Q
What is the problem with the benzene representation with 3dbs? What is the solution?
A
C-C = 0.154nm
C=C = 0.134nm
C-C (benzene) = 0.139nm
BUT all bond lengths are the same
= resonance forms
2
Q
What is a better representation of the benzene ring? Why?
A
Hexagon with a cirlce in the middle
- delocalised pi system above and below the plane
3
Q
What is aromaticity?
A
Electrons are delocalised over the whole conjugated system
4
Q
What are properties of aromatics?
A
Hückel criteria
- conjugated system
- cyclic
- flat
- (4n+2)pie-
5
Q
What are examples that follow the Hückel criteria?
A
- benzene
- piridine
- pyrrole
- imidazole
