Pages in this set

Page 1

Preview of page 1
MODULE ONE: RINGS, ACIDS & AMINES
Aromatic Chemistry

The simplest aromatic compound (arene) is BENZENE (C6H6). A benzene
molecule is usually represented as a hexagon surrounding a circle.

An AROMATIC COMPOUND is any compound with a benzene ring
An ARENE is an aromatic hydrocarbon containing one or more benzene rings…

Page 2

Preview of page 2
Benzene is a colourless liquid with a sweet odour. It is highly flammable and its natural sources
include volcanoes and forest fires. Benzene is a component of crude oil, petrol and cigarette
smoke.

The major problem with benzene is that it is a carcinogen (cancer causing) molecule.



Structure of Benzene…

Page 3

Preview of page 3
C-C Bond Length in Benzene
The Kékulé structure of alternating single and double bonds was represented as a
symmetrical molecule. But C-C single bonds and C=C double bonds have different lengths.

X-Ray diffraction threw some light on the structure. It was found that all the C-C bond lengths in
Benzene…

Page 4

Preview of page 4
The real benzene structure is 152 kJ
mol-1 more stable than the Kékulé
structure.

This energy is known as the
delocalisation energy or resonance
energy of benzene.




Kékulé's structure was disproved:
Bond Length: Double bonds are shorter than single bonds, yet all bond lengths are the same in
benzene. The…

Page 5

Preview of page 5
6 electrons are delocalised in this system.
This means that each C-C has 3 electrons. 2 in the bond and 1 from the delocalised system.
This makes it slightly less electron rich than alkenes which means that they are not as good at
polarising electrophiles.
The bonding in benzene cannot…

Page 6

Preview of page 6
Benzene & Its Reactions
Benzene in toxic and carcinogenic so Methylbenzoate (or Methoxybenzene), a derivative of
benzene is used:




Methoxybenzene is slightly more reactive than benzene. The conditions involving benzene will be more severe.

SUBSTITUTION is a type of reaction where an atom or group of atoms is replaced with…

Page 7

Preview of page 7
Nitration of Benzene
The nitration of benzene is the first step in a historically important chain of reactions. These
lead to the formation of dyes, pharmaceuticals and explosives.

The reaction for the nitration of benzene is:
H2SO4
C6H6 + HNO3 C6H5NO2 + H2O
50°C


Reagents: concentrated nitric acid and concentrated…

Page 8

Preview of page 8
Halogenation of Benzene

The reaction for the Halogenation of benzene is:

C6H6 + X2 C6H5X + HX
Bi-product


Benzene will not react with bromine on its own. It requires the help of a type of catalyst called a
halogen carrier. These halogen carriers include:

FeCl3, FeBr3, AlCl3, AlBr3 (depending on…

Page 9

Preview of page 9
Function of Halogen Carrier (catalyst):
Benzene is more stable than alkenes which means that Cl2 is not a strong enough
electrophile.
Although benzene has delocalised electrons, it is not sufficiently electron rich to polarise
a chlorine molecule like an alkene
The halogen carrier increases the polarization of the Cl-Cl bond,…

Page 10

Preview of page 10
Further Substitution of Benzene
It is possible to substitute more than one functional group. But the functional group already
on the ring affects:
- How easily it can be done
- Where the next substituent goes




Example:




Example:




Methylbenzene
Methyl benzene used to be called Toluene. It has a methyl…

Comments

ethel

Report

doesn't open :/

ethel

Report

can you email it to me plz : [email protected]

lia997

Report

very useful thanks for sharing! :)

Izzy Mason

Report

sooooooooo useful :)

Similar Chemistry resources:

See all Chemistry resources »See all resources »