Aromatic Chemistry (Benzene) Flashcards
What is the observation when benzene is added to bromine water?
Stays orange, no colour change. Saturated.
Describe the thermodynamic stability of benzene
- Kekule’s structure involved 3 double bonds, but benzene has a higher ΔH. Benzene is more energetically stable than cyclohexene.
Describe the bond lengths of benzene.
Bond length of benzene is between a single bond and double bond.
Describe benzene’s system
It has a delocalised system because each C has a 2p electron. They overlap and form a cloud of electron density above and below the plane of the molecule.
What reaction does benzene undergo?
Electrophilic substitution
What is the first step in the nitration of benzene?
Generate the electrophile by adding conc. NH₃ and conc. H₂SO₄
What is the equation for the generation of an electrophile for the nitration of benzene.
H₂SO₄ + NH₃ → HSO₄⁻ + H₂O + NO₂⁺
Describe the mechanism involving benzene.
1) Arrow from e- cloud to NO₂⁺
2) Arrow from bond to H to + in benzene
Generation of electrophile for acylation of benzene
CH₃COCl +AlCl₃ → CH₃CO⁺ + AlCl₄⁻
What is TNT?
Trinitrotoluene
How is TNT formed?
Toluene is benzene with a methyl group. Nitration occurs three times. The alkyl group is electron releasing which makes toluene more reactive than benzene.
How are amines formed?
Nitration of benzene and the addition of catalyst Ni/H₂ or Sn/HCl
Why acylation useful in industry?
Increases the length of the carbon chain.
What is the name of the side chain C₆H₅?
phenyl-
Describe the structure and bonding of benzene
- Each carbon only forms 3 covalent bonds
- Planar and hexagonal
- 120 bond angle
