6.1.1 - Aromatic compounds Flashcards
What is the structure and
formula of Benzene?
C6H6
What is the empirical formula
of Benzene?
CH
What is the state of benzene
at room temperature?
Liquid
What is the bond angle of
benzene?
Bond angle = 120o
What are the 3 features of
benzene that don’t support
Kekule’s model?
● Benzene is resistant to addition reactions
● Enthalpy change of hydrogenation of benzene
is more stable than predicted
● All the carbon bonds are same length
What technique was used to
find the bond lengths of
benzene?
X ray diffraction
What happens to the 4th
electron in the p-orbital of
each carbon atom
in benzene?
It delocalises to form rings of electron
density above and below the hexagon,
forming rings of delocalised electron
density above/below the hexagon.
How do the rings of electron
density affect the stability of
Benzene?
Makes benzene very stable, even though
it is unsaturated (aromatic stability)
Why does benzene have a
relatively high melting point?
Close packing of flat hexagonal
molecules when solid
Is benzene soluble in water?
Explain why?
No because it is non polar
Dangers of benzene - why it is
not used in schools?
It is a carcinogen
Dangers of benzene - why it is
not used in schools?
It is a carcinogen
How do you name compounds
containing a benzene ring?
-benzene, or phenyl- ; can designate
position on ring using numbers if there is
more than one substituent
Why is benzene attacked by
electrophiles?
High electron density above/below ring
due to delocalised electrons
Nitration of benzene is what
type of reaction?
Electrophilic substitution reaction
Which ion is used to nitrate
benzene?
NO₂+
What is the catalyst in nitration
of benzene?
Sulfuric acid
H₂SO₄
How is this NO₂+ ion
generated? (conditions and
equations)
Concentrated H₂SO₄
and concentrated HNO₃
.
Overall:
H₂SO₄ + HNO₃ → HSO₄(-) + NO₂(+) + H₂O
How is the H₂SO₄
catalyst
regenerated in the nitration
of benzene?
HSO₄(-) + H(+) → H₂SO₄
(H+ from benzene ring)
What type of catalyst is used
for a Friedel-Crafts reaction?
A halogen carrier (e.g. AlCl3
)
Why does benzene not react
directly with halogens?
The aromatic ring is too stable
What is happening when AlCl₄-
is formed in terms of
electrons?
The lone pair of electrons on the chlorine
atom is forming a coordinate bond to Al
How is the AlCl3
catalyst
reformed?
AlCl₄(-) + H(+) → HCl + AlCl₃
(H+ from benzene)
How could you use a
Friedel-Crafts mechanism to
add a methyl group to a
benzene ring?
Use a halogenoalkane and AlCl3
to
create an electrophile that can attack
benzene
