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Organic Chemistry II
University of Lincoln
presentation
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Aromatic Hydrocarbons
• Contain double or triple bonds, but do
not show the same reactivity as other
unsaturated hydrocarbons
• Benzene: C6H6
H
• Used mainly as solvents
H
• Substitution rather than
H
Addition is favoured
H
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H
H
Resonance Structure:
Rearrange the bonding electrons
Delocalisation, Resonance:
Stabilise molecules, so make them less
reactive
Three sp2 hybrid orbitals arrange
themselves as far apart as possible
-which is at 120° on a plane. The
remaining p orbital is at right angles
to them.
H
H
H
H
6 p-orbitals
H
H
H
H
H
H
Delocalised
orbital clouds
Each carbon atom uses the sp2 hybrids
to form σ-bonds with two other carbons
and one hydrogen atom.
Delocalised or Conjugated System:
π-bonding electrons can move within
the molecule
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Naming Aromatic Hydrocarbons
CH3
F
Flurobenzene
-ortho
Cl
Ethylbenzene
CH3
NH2
Toluene
O
Aniline
OH
-meta
Cl
OH
Cl
Cl
1,2-Dichlorobenzene
Benzoic acid
Phenol
1,3-Dichlorobenzene
O
Cl
-para
H2C
CH3
-
CH3
+
O
+
N
N
O
O
-
CH3
+
Cl
1,4-Dichlorobenzene
Br
o-Xylene
O
-
N
O
m-Bromostyrene 2,4,6-Trinitrotoluene (TNT)
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Reactions of Aromatic
Hydrocarbons
Substitution
O
• Aromatic Substitution
reaction – Aromatic
compound loses a hydrogen
atom and another atom or
group takes its place.
• It is possible for substitution
to occur in more than one
place on the ring.
O
+
N
O
-
+
O
N
H2SO4
+
Cl2 AlCl3
O
Cl
N
O
H2 O
Br
Br2 FeBr3
O
-
+
+
HNO3
+
O
-
N
-
O
+
N
O
+
O
N
-
O
otha-Dinitrobenzene
meta-Dinitrobenzene
O
-
N
+
O
para-Dinitrobenzene
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Alcohols
• –OH group (hydroxyl group)
• Replace -e with -ol
• CH3OH, methanol, simplest
alcohols are classified as primary (1°), secondary
(2°), or tertiary (3°) depending on the number of
carbon atoms bonded to the carbon bearing the OH group
OH
H3C
H
H
Primary
Alcohol (1o)
OH
H
CH3
CH3
Secondary
Alcohol (2o)
OH
H3C
CH3
CH3
Tertiary
Alcohol (3o)
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Naming Alcohols
H3C
OH
H3C
methanol
OH
OH
CH3
H3C
ethanol
propanol
OH
OH
2-ethyl-1-butanol
or 2-ethyl-butan1-ol
2-propanol or propan-2-ol
or isopropyl alcohol
H3C
H3C
CH3
Polyhydroxy alcohols are alcohols that possess more than one hydroxyl
group
CH3
OH
HO
OH
HO
HO
OH
1,2-Ethanediol
(ethylene glycol)
1,2-propanediol
(propylene glycol)
HO
1,2,3-propanetriol
(glycerol)
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Reactions of Alcohols
■ Reaction with acids to produce Esters
+
O
H3C
+
H3C
HCl or H2SO4 (H Cataly st)
OH
O
CH3
O
OH
Acetic Acid
(ethanoic acid)
CH3
+
H2O
Ethyl acetate
■ Redox reaction (Reduction and oxidation)
Ethanol
H3C
O
Oxidation
OH
H3C
O
Oxidation
H
Acetaldehyde
H3C
OH
Acetic Acid
Reduction
H3C
CH3
Alcohol Dehydrogenase
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Ethers
• –O- group (ether group)
• CH3OCH3, dimethyl ether
simplest
• Soluble in water- H-bonding to
water - Polar
• Flammable – Ether can cause
flash fires
• Low Reactivity – Make Good
Reaction Solvents
• Naming: alkyl groups in
alphabetical order followed by
ether
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Aldehydes and Ketones
• Both contain a carbonyl group (C=O)
H
Aldehyde
R
O
R
Ketone
O
R
Naming
Aldehydes Change -e ending to –al
ethane
ethanal
(acetaldehyde)
Ketones Change -e ending to –one
propane
propanone
(acetone)
H
O
H3C
O
H3C
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CH3
Reactions of Aldehydes and
ketones
Synthesis: produced by oxidation of alcohol
O
H
CH3
CH3
Secondary
Alcohol
H
Tertiary
Alcohol
O
CH3
H3C
OH
H3C
CH3
CH3
Oxidation
Oxidation
Reduction
Primary
Alcohol
OH
Reduction
OH
H3C
H
H
CH3
Cannot be
oxidised
Reduction of carbonyl group to produce alcohols
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Oxidation of carbonyl group
H
H3C
O
H
HO
Carboxylic acid
H3C
O
O
H3C
Strong
Oxidation
Reduction
H3C
Oxidation
Reduction
H3C
O
HO
+
O
HO
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Carboxilic acids
• Contains C=O and –OH group on same
carbon
• Change -e to -oic acid
• Acetic acid: acid in vinegar
• Simplest: methanoic acid
(formic acid)
O
O
HO
H
Methanoic acid
HO
O
CH3
Ethanoic acid
HO
CH3
Propanoic acid
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Reactions of Carboxilic acids
■ Esterification reactions
+
O
+
H3C
H3C
CH3
HCl or H2SO4 (H Cataly st)
OH
O
O
OH
Acetic Acid
(ethanoic acid)
CH3
+
Ethyl acetate
■ Reduction to aldehydes
O
H
O
Oxidation
CH3
Reduction
HO
CH3
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H2O
Ester
• Derived from carboxylic acids and alcohols
• Tend to be fragrant
– Methyl butyrate
– Ethyl butyrate
apple
pineapple
• An ester name has two parts - the part that
comes from the acid (propanoate) and the
part that shows the alkyl group (methyl).
O
Example: Methyl propanoate H C
CH
3
3
O
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Reactions of Esters
Substitution
R2OH
R
R
R
R+
O
1
Reduction of esters
O
O
R2
O
H2O
Ester
LiAlH4
H
O
R
Acid
O
O
H
O
+
R2
H
R1
R1
+
R2
OH
OH
R2NH
base
R
NH
R2
Amide
Hydrolisis of esters (basic)
O
O
+
R
O
Carboxylate
ester
saponif ication
NaOH
or hy droly sis
R1
+
R
-
O
Sodium
hydroxide
HO
R1
+
Na
Sodium
Carboxylate
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Alcohol
Amines
• Derived from ammonia by substituting H for
alkyl groups. It is an alkali
• We have primary, secondary or tertiary
amines depending on the number of H
substituted
N
H
N
H
H
Ammonia
R
N
N
H
H
Primary
amine (1o)
R
H
R1
Secondary
amine (2o)
R
R2
R1
Tertiary
amine (3o)
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Amines
CH3
NH2
H2N
NH2
1,4-butanediamine
Putrescine (found in decaying meat) (1o)
Amphetamine
(dangerous stimulant) (1o)
CH3
N
N
H
Piperidine
H2N
H3C
CH3
Triethylamine (3o)
H3C
CH3
NH2
Isopropylamine (1o)
NH2
1,5-pentanediamine
Cadaverine (found in the putrefaction of cadavers
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Reactions of Amines
Alkylation
H
R
R
X
+
2 R1
N H
NH2
+
+
R1 N
R1
H
Oxidation reduction
O
-
+
O
NH2
N
+
H Na
Reduction
Oxidation
Phenylamine
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Acknowledgements
•
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•
•
•
•
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JISC
HEA
Centre for Educational Research and Development
School of natural and applied sciences
School of Journalism
SirenFM
http://tango.freedesktop.org
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