Aromatic Chemistry Flashcards
What is an aromatic compound?
A compound containing a benzene ring
What is the formula of benzene?
C6H6
Explain the Kekule structure of benzene
6 carbon hydrocarbon which was thought to have alternating single and double bonds. expected to act as an alkene and decolourise bromine.
What evidence was there to show that the Kekule structure was incorrect?
X ray diffraction data showed that the length of all the bonds was the same (but single and double bonds all have different lengths)
Didnt decolourise bromine
Didnt undergo electrophilic addition reactions
Explain the resonance hybrid model of benzene
Benzene existed in rapid equilibrium of the two forms of the Kekule structure so they moved to quickly for bromine to add onto the benzene
Name today’s accepted model of benzene
Molecular orbital model
Describe and explain the structure of benzene
Planar 6 carbon hydrocarbon where all bond lengths are the same
Each carbon has 3 sp2 orbitals at 120 degrees to each other
2 p orbitals which protrude above and below each carbon
P orbitals overlap to form a delocalised pi system
Why is benzene so stable?
p electrons are delocalised into the pi system so there’s less repulsion so lower energy so less reactive
What are the properties of benzene?
Colourless liquid at room temp
High boiling and melting point
Non-polar
Toxic vapours
What reactions can benzene undergo
Combustion
Electrophilic substitution
What are the conditions for the nitration of benzene?
Concentrated sulfuric acid
Concentrated nitric acid
50 degrees
What happens in the nitration of benzene?
NO2 is added onto the benzene
Give the reactions which occur in the nitration of benzene
HNO3 + H2SO4 —> HSO4- + H2NO3+
H2NO3+ ——> NO2+ + H2O
H2SO4 + H2O —-> HSO4- + H3O+
Give the overall equation for the nitration of benzene
HNO3 + H2SO4 —-> NO2+ + H3O+ + 2HSO4-
What are the uses of nitrobenzene?
Explosives
Amines
Organic synthesis
