Aromatic Chemistry Flashcards
What is benzene’s molecular formula
C6H6
Explain benzene structure
Six carbon in a hexagonal ring ,with one hydrogen bonded to it
Each C atom is bonded to two other C atoms and one H atom by single covalent σ- bonds
Describe the shape of benzene
It is planar
Hexagonal
C-C bonds are equal in length
Describe the nitration reaction of benzene
Reagents:concentrated nitric acid
Catalyst:sulfuric acid
Mechanisms:electrophilic substitution
Electrophile:NO2
What is the overall equation for the formation of the electrophile
HNO3 + 2H2SO4 —>NO2+ +2H2SO4- + H3O+
What is the by product of the nitration reaction
H+
What is the functional group change in friedel crafts acylation
Benzene - phenylketone
What are the reagents for friedels crafts acylation
Acyl chloride and aluminium chloride catalyst
What is the equation for the formation of the electrophile for friedel crafts
AlCl3 + CH3COCl —> [CH3CO]+ + [AlCl4]-
What is the bond angle in benzene
120
Describe the delocalisation of benzene ring
The six p electrons are delocalised in a ring structure above and below the plane of carbon atoms.
Why is there delocalised electrons
Each C atom is bonded to two other C atoms and one H atom by single covalent σ-bonds.
This leaves one unused electron on each C atom in a p orbital, perpendicular to the plane of the ring
How is a pi bond formed
Spare electrons in the p orbital overlap
Compare the stability of benzene with cyclohexa-1,3,5- triene
Benzene is more stable
Expected hydrogenation of cyclohexantriene is -360
Whilst benezene is -208
Less exothermic by 152 kj
Does cyclone a-1,3 diene have delocalisation
Yes it does
Describe delocalisation in cyclohex-1,3-diene
The pi binds close together and so overlap
Hydrogenation would be less negative
In cyclohexa-1,4-diene is there delocalised
No because the pi electrons are too far apart and don’t overlap
