1629508
Description
Mind Map by tommyshellerpaulson, updated more than 1 year ago
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Created by tommyshellerpaulson
over 9 years ago
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Unit 4: Module 1 -
Rings, Acids and
Amines
- BENZENE: Structure
- Formula: C6H6
- Cyclic
- Two ways of representing it...
- Kekule's
- If it was correct..
- 3 x length of C-C bonds (147pm)
- 3 x length of C=C bonds (135pm)
- HOWEVER
- X-ray diffraction have
shown all the bond lengths
have the same value
(140pm)
- X-ray diffraction have
shown all the bond lengths
have the same value
(140pm)
- Hydrogenation Enthalpy Change of C=C bond is -120 Kj/mol
- so with 3 C=C bonds, enthalpy change should be -360 Kj/mol
- HOWEVER
- Experimental enthalpy change is
-208 Kj/mol...... Far less exothermic
than expected
- Indicates that Benzene is more
stable than the Kekule
structure would be. This is
thought to be due to the
delocalised electrons.
- Indicates that Benzene is more
stable than the Kekule
structure would be. This is
thought to be due to the
delocalised electrons.
- Experimental enthalpy change is
-208 Kj/mol...... Far less exothermic
than expected
- HOWEVER
- so with 3 C=C bonds, enthalpy change should be -360 Kj/mol
- 3 x length of C-C bonds (147pm)
- If it was correct..
- Delocalised Model
- P-Orbitals of all 6 Carbon
atoms overlap to create Pi
Bonds
- 3 Electrons in the top ring, 3 in
the bottom ring (due to the
repulsion of negative charges)
- 3 Electrons in the top ring, 3 in
the bottom ring (due to the
repulsion of negative charges)
- P-Orbitals of all 6 Carbon
atoms overlap to create Pi
Bonds
- Kekule's
- Two ways of representing it...
- Formula: C6H6
- BENZENE: Aromatic Compounds
- Compounds containing a benzene ring are
called arenes or 'aromatic compounds'
- Chlorobenzene
- Nitrobenzene
- 1,3-dimethylbenzene
- Chlorobenzene
- Others are named as compounds with a phenyl group (C6H5) attached
- Phenol
- 2-methylphenol
- phenylamine
- Phenol
- Compounds containing a benzene ring are
called arenes or 'aromatic compounds'
- Reactions with Benzene
- Alkenes react easily with
Bromine water (the famous
experiment where Br water
decolourises)
- If the Kekule model was correct, Benzene would
be expected to react similarly (due to the C=C
bonds)
- Because of the electron rings above and
below the carbon atoms, it makes the
benzene ring VERY staable, and spreads out
the negative charge.
- This means Benzene is very unwilling to undergo
addition reactions which would destroy the stable ring
- Instead, benzene prefers to react by electrophilic substitution
- Electrophile: Positively charged
ions or polar molecules that are
attracted to ares of high electron
density
- Arenes undergo
Electrophilic
Substitution with....
- With Nitric Acid and a
Catalyst (this catalyst is
Sulfuric acid)
- Sulfuric acid (how to
make the NO2+)
- Sulfuric acid (how to
make the NO2+)
- HALOGENS using a
HALOGEN CARRIER
- PICTURE OF BROMINE OR CHLORINE
REACTING WITH BENZENE IS TOO BLOODY
HARD TO FIND - JUST LEARN IT
- PICTURE OF BROMINE OR CHLORINE
REACTING WITH BENZENE IS TOO BLOODY
HARD TO FIND - JUST LEARN IT
- With Nitric Acid and a
Catalyst (this catalyst is
Sulfuric acid)
- Electrophile: Positively charged
ions or polar molecules that are
attracted to ares of high electron
density
- Instead, benzene prefers to react by electrophilic substitution
- This means Benzene is very unwilling to undergo
addition reactions which would destroy the stable ring
- Because of the electron rings above and
below the carbon atoms, it makes the
benzene ring VERY staable, and spreads out
the negative charge.
- If the Kekule model was correct, Benzene would
be expected to react similarly (due to the C=C
bonds)
- Alkenes react easily with
Bromine water (the famous
experiment where Br water
decolourises)
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