Aromatic compounds Flashcards
1
Q
What is the structure of benzene?
A
C6H6
2
Q
What are the 6 issues with the Kekule model?
A
- Makes bonds look different lengths when they are all exactly the same length
- C=C suggests benzene would have isomers due to the restricted rotation but benzene has no isomers
- Benzene doesn’t undergo addition reactions like alkenes
- Electron densities around carbon atoms are symmetrical which you can see on x ray diffraction
- Enthalpy of hydration is far less exothermic than expected -360 vs -208 kJ the difference is known as a delocalisation energy so benzene is more stable due to the delocalised ring of electrons
3
Q
What is the delocalised model?
A
Each carbon atom forms 3 sigma bonds due to the head on overlap of atomic orbitals
1 remaining p orbital containing electrons sticks out above forming a ring of delocalised electrons above and below
4
Q
How does benzene burn?
A
With a smoky flame 2C6H6 + 15O2 = 12CO2 + 6H2O
5
Q
What are arenes?
A
Compounds derived from benzene
6
Q
Why does benzene have high melting points?
A
High stability of delocalised benzene ring
7
Q
What reactions do arenes undergo?
A
Electrophillic substitution reactions
8
Q
What is an electrophile?
A
Electron pair acceptor
