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1
B15
Medicines by Design..
Revision of reagents, conditions and
reaction types.
Click to go to a particular section……
Aliphatic chemistry reagents and conditions
Aliphatic chemistry reaction types
Aromatic chemistry reagents and conditions
Aromatic chemistry reaction types
 Key words and definitions.




A10. Aliphatic Reactions. Add the
reagents and conditions.
R
H
R
C
C
H
O
9
2
CH2
2
O
9
C
R
OH
R
C
R
H
O
R'
8
X10
4
SCl2O
Heat + reflux
1
5
7
O
R
CH2
1
R
Br
CH2
CN
R
4

6

O
R
R
CH2
NH2
R
CH2
Click here to go back to the menu
COOH
C
NH
C
NH2

CH3
O
R
Cl
Dil H2SO4
Heat + reflux
3
6
C
NaCN in ethanol/H2O
Heat + reflux
R
C
OH
9
H
O
7
R'

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Notes
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3
A12. Aliphatic reagents and conditions
X12
O
R
O
H
C
R
C
H
CH2
O
C
R
OH
R
C
H
R
OH
H
C
O
O
R
CH2
R
Br
CH2
CN
R
O
C
R
Cl
O
R
CH3
R
CH2
NH2
R
CH2
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COOH
C
NH
C
NH2

R
R'
R'
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reagents and conditions
4
A11. Aliphatic reagents and conditions
X11
H
C
Al2O3
300oC
R
C
H
CH2
R’OH/conc H2SO4 cat
Heat + reflux
O
O
C
R
OH
H
O
H
NaBH4
Room temp
NaOH(aq)
Heat + reflux
Dil HCl or H2SO4 or
NaOH
Heat + reflux
C
R
OH
SCl2O
Heat + reflux
Conc
HBr
Room
temp
NaBr(s) + conc H2SO4
heat + reflux
R
H2/Ni cat
150oC + 5 atm
CH2
R
Br
CH2
CN
R
C

R’NH2
Room temp
Conc NH3
Heat + reflux
Dil H2SO4
Heat + reflux
R
CH3
R
CH2
NH2
R
CH2
COOH


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C
NH
C
NH2
O
R
R'
O
R
Cl
NaCN in ethanol/H2O
Heat + reflux
Br2(l)
sunlight
O
Conc NH3
Room temp
O
R
C
R’OH
Room temp
R
K2Cr2O7(aq)/dil H2SO4
heat + reflux
K2Cr2O7(aq)/dil H2SO4
heat + reflux
R'
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5
A13. Aliphatic Reactions. Add the reaction types.
X13
O
R
O
H
C
R
C
H
CH2
O
C
R
OH
R
C
H
R
OH
H
C
O
H2/Ni cat
150oC + 5 atm
O
R
CH2
R
Br
CH2
CN
R
O
C
R
Cl


O
R
CH3
R
CH2
NH2
R
CH2
COOH
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C
NH
C
NH2

R
R'
R'

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Key words and
definitions for help
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6
A14. Aliphatic Reaction types
X14
R
H
C
Elimination or
dehydration
Oxidation
R
C
H
CH2
Oxidation
Esterification or
condensation
O
O
C
R
OH
R
C
H
R
OH
Reduction
H
Addition or
hydrogenation
CH2
R
Br
CH2
CN
R
Nucleophilic
substitution or
acylation
C
Nucleophilic
Substitution or
acylation
Nucleophilic
substitution
Hydrolysis
O
R
CH3
R
CH2
NH2
R
CH2
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COOH
C
NH
C
NH2



R
R'
O
R
Cl
Nucleophilic
substitution
Radical
substitution
O
Nucleophilic
substitution or
acylation
O
R
C
Hydrolysis
Nucleophilic
substitution
Nucleophilic
substitution
Electrophilic
addition
O
R'
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7
A1. The addition reactions of alkenes with the following:
bromine, hydrogen in the presence of a catalyst, hydrogen
bromide, and water in the presence of a catalyst.
CI 12.2
Ethene is unsaturated it has a double C to C bond. It undergoes electrophilic addition reactions in
which another molecule is added on. A saturated compound is produced.
a.
Ethene with bromine (g) or (l) or dissolved in an organic solvent.
Ethene will decolourise orange bromine; it reacts rapidly to form a colourless compound. This
occurs at room temperature.
H H
H2C CH2(g)
+ Br
Br(g)
H C C H(l)
Br Br
1,2-dibromoethane (colourless)
R
(reagent) is Br2(g) or Br2(l) or Br2 in an organic solvent. (NB Salters includes catalysts in this
category if required)
C
b.
(conditions) are room temperature. (NB Salters includes pressures here if required).
Ethene with Bromine water Br2(aq)
H H
H2C CH2 (g)
+
Br2 (aq)
+
H2O(l)
H C C H (l)
Br OH
(orange)
a bromoalcohol (colourless)
Bromine water (bromine dissolved in water) is more convenient and safer to use as a test of
unsaturation, than bromine(g) or bromine(l) or bromine dissolved in an organic solvent such as
cyclohexane.
R
C
(reagent) is Br2(aq)
(conditions) are room temperature.
Back to map
+
HBr(aq)
8
C. Ethene with concentrated hydrobromic acid, HBr(aq)
CH2
CH2
+
HBr
CH3
CH2Br
Bromoethane (now saturated)
R
conc. HBr(aq)
C
room temperature.
d. Ethene with hydrogen(g)
CH2
Hydrogenation
CH2
+
H2
CH3
CH3
ethane
R
H2(g) and Ni (or Pt) catalyst, finely powdered
C
1500C and 5 atm with the Ni. (or room temp. and pressure with the Pt).
NB Pt is white gold:- very expensive
e. Ethene with water H2O(g) (it is steam at 3000C)
The catalyst is phosphoric acid absorbed onto silica ( I imagine silica as being like pure white
sand and that it is soaked in the acid which is a liquid).
CH2
CH2
+
H2O
CH3
CH2OH
ethanol
R
C
H2O(g) cat. Phosphoric acid absorbed onto silica.
3000C and 60 atmospheres pressure.
Note:
 Reactions a,b,c,d, and e are all examples of addition reactions.
 Reactions a, b, c and e are examples of electrophilic addition reactions.
 Reaction d involves a catalyst and has a different mechanism.
Back to map
9
The mechanism of the electrophilic addition reaction between
bromine and alkenes.
CI 12.2
Mechanism for reaction in a above
H
curly arrows
H
C
show movement of a
pair of electrons.
H
C
H
H
H
Br 
C
Br
Br 
+
C
H
+
H
Br
a carbocation and a bromide ion

The bromine molecule is polarised i.e. it has a + and a atom, like when the bond is polar. This happens because the
electrons in the Br2 molecule are repelled by the electrons
in the C=C.
The Br + end now acts as an electrophile. Electrophiles
are attracted to a negatively charged region (the C=C is
made up of 4 electrons) and go on to accept a pair of
electrons (2 points in the definition).





The carbocation has a C with a
positive charge.
That C had a half share of the
two electrons in the bond, which
was broken.
It now has no share
of that pair.
It is now a C atom with one less
-
e so it has a single + charge.
NB
philic means like
phobic means hate



The bromide ion is written
Br
One of the lone pairs has come from the bond in the Br2 molecule.
It had a share of the bonding pair, but now has both electrons.

It has now overall gained an electron, so the Br atom now has a
- charge.
Then we have the next step:
H
H
C
Br
Br
C
+
H
H
H
H
H
C
C
H
Br Br
1,2-dibromoethane
This is electrophilic addition. It is very important that you understand this mechanism and are
able to explain it. The other reactions of ethene proceed by a similar mechanism.
10
A2. The dehydration of alcohols to form alkenes.
CI 13.4
In a dehydration reaction, a molecule of water is lost. Sometimes, this is called an elimination reaction.
Saturated  Unsaturated
This is the reverse of an addition reaction.
E.g. CH3CH2OH  CH2=CH2 + H2O
Reagents: Ethanol passed over
alumina (Al2O3) catalyst.
Conditions: 300oC
What are the alternative reagents and conditions for this reaction?
NB Phenols and carboxylic acids do not undergo dehydration reactions.
The meaning of the term elimination reaction.
CI 13.4
In an elimination reaction, a small molecule (e.g. water) is lost. Dehydration of alcohols are elimination
reactions.
Write 2 equations for the elimination of water from propan-1-ol. In the first, use full structural
formulae. In the second, use skeletal formulae.
Back to map
11
A3. The reaction of alkanes with halogens.
CI 6.3
Examples:
CH4 +
C6H14 +
Cl2  CH3Cl +
Br2  C6H13Br +
HCl :equation (1)
HBr
These are both radical substitution reactions where the halogen replaces hydrogen. This type of
reaction leads to a mixture of halogen substituted products because we cannot control the radicals that
are produced.
Mixture of products
The reaction of methane (CH4) with chlorine in the presence of sunlight proceeds via a radical chain
reaction. The overall equation for the reaction is equation (1) above.
Complete the reaction mechanism below:
Initiation:
Cl2 h
2Cl.
Propagation:
CH4 + Cl.  CH3. + HCl
CH3. + Cl2  CH3Cl + Cl.
(chloromethane made)
CH3Cl + Cl.  CH2Cl. + HCl
CH2Cl. + Cl2  CH2Cl2 + Cl. (dichloromethane made)
Termination:
Back to map
12
A4. Nucleophilic substitution reactions of the
halogenoalkanes with hydroxide ions and ammonia.
CI 13.1, Act A4.1b
The feature of a halogenoalkane molecule that allows it to undergo substitution reaction is the presence
of a polar bond between the halogen atom and the carbon atom to which it is bonded. The halogen
atom is slightly negatively charged and the carbon atom is slightly positively charged. This carbon
atom is attacked by nucleophiles.
+
C
-
Br
Why is the carbon – halogen bond polar?
Complete this table for 2 common nucleophiles:
Formula
Structure
(inc. lone pairs)
OH -
_
..
:O:H
..
Reaction
R-X + OH-  R-OH + X-
Organic product
Alcohol
Amine
NH3
The mechanism of nucleophilic substitution in halogenoalkanes.
CI 13.1
In general:
where X – is any nucleophile and the curly arrow shows the movement of a pair of electrons.
The C – Hal bond will break heterolytically !
Back to map
13
A5. An outline of the preparation of a halogenoalkane from
an alcohol.
Act A4.2
One way to make a halogenoalkane is to start with an alcohol and replace the – OH group by a
halogen atom.
Reaction in Activity A4.2:
CH 3
CH 3
CH 3
C
OH
+
CH
H Cl
3
Cl
+
CH 3
CH 3
2 – methylpropan – 2 – ol
C
2 – chloro – 2 methylpropane
This is an example of nucleophilic substitution – the alcohol group is first protonated in the strongly
acid solution before it can be displaced by the Cl – nucleophile ( water is lost).
Give the mechanism for this reaction: (CI 13.1, page 303 may help)
R
NaBr(s) and concentrated H2SO4
C
Heat and reflux
Back to map
H2O
14
A6. Amines can act as nucleophiles with acyl chlorides
CI 13.8
ammonia / amines react with acyl chlorides:
ammonia
primary amine
+
+
acyl chloride
acyl chloride
primary amide +
secondary amide +
HX
HX
These are nucleophilic substitution reactions.
Complete the following equations;
O
+
H N H
Cl
H
C
+
CH3
primary amide
an acylchloride
ammonia
O
CH3 N
H
+
Cl
C
+
CH3
H
methylamine
(a primary amine)
an acylchloride
secondary amide
These reactions are very vigorous even at room temperature.
O
+
CH3
-
C
Cl
-
The C has two more electronegative
groups attached so
they are very attractive to nucleophiles
e.g. NH3, amines.
The reactions of amines and acyl chlorides are sometimes called acylation
reactions.
Back to map
15
A7. Ester formation from alcohols or phenols
CI 13.5
Esters are named after the alcohol and the acid from which they are made:
Complete the following table:
Acid
Alcohol
Resulting Ester
O
H C
O
H
C
H
methyl methanoate
H H
O
H C OH
H C C C
OH
H H
propanoic acid
H C
H
O
OH
methanoic acid
H
methanol
H H H
H C C C OH
H H H
propan-1-ol
Back to map
H
16
Examples:
Acid
water
a.
+
O
H C
C
3
alcohol
+
C
OH
ethanoic acid
methanol
+
H3C C
OH
ethanoic acid
H C
3
O
CH
+
H C C OH
+
O
+
C
3
O
CH CH
2
H H
+
ethyl ethanoate
ethanol
H H H
+
H C C C OH
O
H H H
+
O
H
3
water
H O H
CH2 CH2 CH3
+
propyl ethanoate
propanol
H
+
H3C C
H
water
+
O
O
3
methyl ethanoate
H C
H
+
C
H H
c.
O
O
H C OH
O
3
water
H
ethanoic acid
H C
+
H
OH
b.
ester
water
N.B. All of these reactions in which esters are made are reversible reactions.


The forward reaction is called esterification
The backward reaction is called hydrolysis. In Act WM2, an ester was hydrolysed. The catalyst
was sodium hydroxide solution.
When making an ester using a phenol rather than an alcohol, a more vigorous reagent than a carboxylic
acid is needed. The OH group in a phenol is less reactive than the OH group in an alcohol.
Method 1
OH
Phenol
+
+
O
HO
O
O C CH3
C CH3
carboxylic acid
ester
(conc. H2SO4 catalyst and heat under reflux is needed even with an alcohol).
Back to map
+water
+
H2O
17
Method 2
OH
O
O
+
O
Phenol +
O
C CH3
O C CH3
C CH3
acid anhydride
ester
+
+
HO
O
C CH3
carboxylic acid
(This does not need heat and reflux. It is reactive but not too dangerous. This method was used to make
aspirin in WM.)
Method 3
OH
Phenol +
+
O
Cl
O
O C CH3
C CH3
acyl chloride
ester
+
HCl
+ hydrochloric acid
(Faster but ethanoyl chloride is toxic and hazardous as it is so very reactive.)
Why do you think both methods 2 and 3 must be carried out in the absence of
water?
Both acid anhydrides and acyl chlorides are called acylating agents:
-OH on alcohol or on phenol is replaced by
R C
O
in the ester. This is an acyl group.
O
Back to map
18
A8. The hydrolysis of esters
CI 13.5
The reverse of esterification is hydrolysis. Hydrolysis is bond breaking involving water.
H H
O
H C
+
C
3
O
CH CH
2
H
O
H C C OH
+
H C
H H
3
Ethyl ethanoate +
O
H
water
ethanol +
ethanoic acid
On hydrolysis, the sweet smell of the ester disappears. To speed up this reaction NaOH(aq) is often
used, when heating under reflux. This reaction was used in the hydrolysis of Oil of Wintergreen in
WM.
What ion is produced instead of ethanoic acid if NaOH(aq) is used as a catalyst?
Give name and full structural formula.
What needs to be added now to produce ethanoic acid from the ethanoate ion?
A9. The following reactions involving aldehydes and ketones:
formation by oxidation of alcohols, oxidation to carboxylic
acids and reduction to alcohols.
CI 13.7
Recognising aldehydes and ketones.
Aldehydes and ketones are both carbonyl compounds which have the carbonyl group:
O
C
Back to map
3
C
OH
19
Aldehydes are made when a primary alcohol is oxidised.
H O
examples:
(2 C’s => eth suffix al)
H C C H
23
24
H
ethanal
H
H
H
O
C
C
C
(3 C’s => prop, suffix al)
H
H H
propanal
In aldehydes the carbonyl group is always on the end of the C chain so no number is required in the
name.
Ketones are made when a secondary alcohol is oxidised.
O
examples:
H3C
C
41
CH3
propanone
H
H
C
44
H
C
45
H
O
C
C
46
47
H
C
48
H
H
H
pentan-2-one
H
(The carbonyl group is midway along the carbon
chain. A number may be required to show which
C atom has the carbonyl group)
H
Formation of aldehydes and ketones from alcohols.
Remember a triangle!
1ry alcohol
oxidation
2ry alcohol
oxidation
aldehyde
oxidation
carboxylic acid
ketone
3ry alcohol
A good oxidising agent is acidified potassium dichromate (VI) solution.
Back to map
20
Here is the half equation showing what happens to the dichromate ions:
Cr2O72- + 14H+ + 6e-  2Cr3+ + 7H2O
6+
(acid)
3+
orange
green
This is the half equation for the oxidation of ethanol:
CH3-CH2-OH + H2O  CH3CHO + 2H+ + 2e-
Combine the 2 half equations above and write an overall
equation for the redox reaction:
Definitions of oxidation are:
 Gain of oxygen
 Loss of hydrogen
 Loss of electrons
 Increase in oxidation number.
Give four definitions of reduction:
Is the chromium in the half equation above oxidised or reduced?
A closer look at the reaction of the 1ry alcohol:
H
H
H
H
O
O
H
C
C
OH
H
C
H
C
C
OH
H
H
1ry alcohol
Back to map
H
a
H
H
aldehyde
b
C
carboxylic acid
21
Why are both of these steps described as oxidation?
a.
b.
A closer look at the reaction of a 2ry alcohol:
H
H
H
H
C
C
C
H
OH
H
H
H
H
2ry alcohol
H
H
C
C
C
H
O
H
H
H
ketone
carboxylic acid
Why doesn’t oxidation of the ketone occur?
A closer look at the reaction of a 3ry alcohol:
H
H
H
H
C
H
C
C
C
H
OH
H
H
H
3ry alcohol
H
H
H
C
C
C
H
O
H
ketone
Why doesn’t oxidation of a 3ry alcohol occur?
Back to map
H
C
C
H
O
OH
22
NB. Phenols and carboxylic acids are not oxidised either!
It is important that you can quote the reagents and conditions for these oxidations:
Reagents – K2Cr2O7(aq), dilute HCl(aq) or dilute H2SO4(aq)
Conditions – Heat and reflux.
If oxidation occurs, there will be a colour change from orange to green.
Reduction of carbonyls to alcohols.
Aldehyde  1ry alcohol
Ketone  2ry alcohol
R = NaBH4(aq)
C = room temperature
Name the reagent:
Give the formulae of the carbonyl componds which would be reduced to these alcohols:
This would be reduced to the alcohol on the
right…..
CH3
This would be reduced to the alcohol on the
right…..
CH2
OH
CH3
CH
CH
CH3
CH3
C
CH3
Back to map
CH3
CH2
OH
Aromatic. Add the reagents and conditions.


Cl
Br
23

R7
1
H2(g), Ni cat
300oC, 30 atm.
SO2OH
1

2
3.
NO2
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Sn + conc HCl
Heat + reflux
NH2
6
4
5
+
N
N Cl-
O
R
C
6
R
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N
N
OH
24
Aromatic reagents and conditions
Cl
Br



R8
Br2(l), FeBr3 cat
room temp.
H2(g), Ni cat
300oC, 30 atm.
SO2OH
conc. H2SO4.
heat + reflux.
Cl2(g), AlCl3 cat
room temp/ anhydrous
conc. HNO3, conc. H2SO4 cat
<55oC.
RCl(l), AlCl3 cat
heat + reflux/ anhydrous.
NO2
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Sn + conc HCl
Heat + reflux
NH2
NaNO2(aq)/dil HCl
<5oC
RCOCl(l), AlCl3 cat.
heat + reflux/ anhydrous
+
N
N Cl-
O
R
C
alkaline phenol
<5oC
R
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N
N
OH
25
Aromatic reagents and conditions
Cl
Br


R9
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and conditions.
NH2
NO2
SO2OH
+
N
N Cl-
O
R
C
R
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N
N
OH
26
Aromatic Reaction types

Cl
Br


C10

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NH2
NO2
SO2OH
+
N
N Cl-
O
R
C
R
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N
N
OH
27
Aromatic reaction types
Cl
Br



C11
Electrophilic
substitution
Hydrogenation
SO2OH
Electrophilic
substitution
Electrophilic
substitution
Electrophilic
substitution
Electrophilic
Substitution or
Friedel Crafts alkylation
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NO2
NH2
Reduction
Diazotisation
Electrophilic
Substitution or
Friedel Crafts acylation
+
N
N Cl-
O
R
C
R
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Coupling
reaction
28
R1. Halogenation of the ring in arenes.
CI 12.4.
Electrophilic Substitution……
Step 1:
The bromine molecule is polarised as it
approaches the benzene ring.
+
+
Br
Br
Br +
-
BrBr
The FeBr3 helps to polarise the bromine
by accepting a lone pair of electrons from
one of the bromine atoms.
FeBr4-
FeBr3
The bromine molecule is so polarised that
it splits.
Step 2:
Br
Br+
FeBr4-
Br+ becomes bonded to a ring C and
H+ is lost. Br+ is an electrophile:
 Has a + charge
 Attracted to electron rich centre
 Accepts pair of electrons to form
a dative covalent bond.
R
C
E
H
The H+ reacts with the FeBr4-.
Br
FeBr3
FeBr3 is regenerated as it is a catalyst
in the reaction.
Why does the benzene attract electrophiles?
Br2(l) and either FeBr3 or Fe(s)
Room temperature.
C6H6 + Br2  C6H5Br + HBr
What would the formula of the product have been if addition had occurred rather than
substitution?
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29
Chlorine reacts in a similar way to bromine. Complete the
mechanism:
Electrophilic Substitution……
Step 1:
The chlorine molecule is polarised as
it approaches the benzene ring.
+
+
Cl
Br
Br +
-
ClBr
The AlCl3 helps to polarise the chlorine by
accepting a lone pair of electrons from one
of the chlorine atoms.
FeBr4-
AlCl33
FeBr
The chlorine molecule is so polarised that
it splits.
Step 2:
Br
Br+
FeBr4-
Cl+ becomes bonded to a ring C and
H+ is lost. Cl+ is an electrophile:
 Has a + charge
 Attracted to electron rich centre
 Accepts pair of electrons to form
a dative covalent bond.
The H+ reacts with the AlCl4-.
R
Cl2(l) and AlCl3(s)
C
Room temperature, anhydrous.
E
C6H6 + Cl2  C6H5Cl + HCl
Back to map
H
Br
FeBr3
AlCl3 is regenerated as it is a catalyst
in the reaction.
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R2. The nitration of benzene.
CI 12.4.
Electrophilic substitution.
R
Conc. Nitric acid and conc. sulphuric acid as a catalyst.
< 55oC. Explain why…..
C
E
C6H6 + HNO3  C6H5NO2 + H2O
Step 1:
HNO3 + 2H2SO4
NO2+ + 2HSO4- + H2O
The nitrating mixture
NO2+ is an electrophile.
Step 2:
NO2
NO2+ + HSO4 -
Why do we say that the sulphuric acid is a catalyst?
Back to map
+ H2SO4
31
R3. The sulphonation of benzene.
CI 12.4.
Electrophilic substitution.
O
OH
S
E
+ H2SO4
R
Conc. sulphuric acid
C
Heat and reflux
Draw the structural formula of
the electrophile and name it:
.
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O
+ H2O
Name the organic product of
this reaction:
32
R4. The Friedel-Crafts alkylation of benzene.
CI 12.4
Electrophilic substitution
CH3
E
+ CH3Cl
+ HCl
Why Friedel-Crafts?
Why alkylation?
Give the reagents and conditions:
R
C
How would you do this experiment differently if you wanted to make ethylbenzene rather than
methylbenzene?
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33
R5. The Friedel-Crafts acylation of benzene.
CI 12.4.
In these reactions, an acyl group is introduced into the
benzene ring.
O
C
CH3
Acyl chlorides also have acyl groups in. Draw the full
structural formula of propanoyl chloride and also circle the
acyl group:
O
O
E
+
CH3 C
R
Give the reagents:
C
Give the conditions:
C
CH3
Cl
+ HCl
Friedel-Craft reactions are so useful to Chemists because they provide a way of adding carbon atoms to
the benzene ring.
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34
R6. The formation of azo dyes by coupling reactions
involving diazonium compounds.
CI 13.10.
Coupling reactions:
Diazonium salt + Coupling agent  Azo compound
Diazonium salts:
A typical diazonium salt is benzenediazonium chloride;
+
N
Cl-
N
This is made from phenylamine. The reaction is called diazotization.
+
NH2 + HNO2 + HCl
N
N
R = NaNO2(aq) and dilute HCl
Name the reagents:
Why does the temperature have to be less than 5oC?
Azo compounds:
This is an azo compound. Circle the azo group:
R
N
Back to map
N
R'
Cl- + 2H2O
35
If R and R’ are aromatic then the azo compound is more stable than if they were
aliphatic. This is because the azo compound then has an extended delocalised system
of electrons. Aromatic azo compounds are coloured and used as dyes.
The coupling agent reacts with the diazonium salt to make the azo compound.
The coupling agent is another compound containing a benzene ring e.g. phenol or
phenylamine.
+
N
N
Cl- +
OH
N
N
Name the 2 organic reagents above…..
R = The phenol is in an alkaline solution for this reaction.
C = At temperature less than 5oC, the coloured azo compound is
formed immediately.
Is the diazonium salt an electrophile or a nucleophile here?
What colour is the azo compound above?
Write the equation for the formation of another azo
compound:
Back to map
OH + HCl
36
Key Words
Acylation
The introduction of an acyl group, RCO-, using an acyl chloride.
Typical of alcohols, amines, ammonia and arenes.
Addition
The addition of atoms or groups of atoms across a double bond.
Typical of alkenes, aldehydes and ketones.
Alkylation
The introduction of an alkyl group, R, using a chloroalkane.
Typical of arenes.
Carbocation
An organic molecule containing a carbon atom with a + charge.
Intermediates in the electrophilic addition reactions of alkenes.
Condensation
A reaction in which two molecules join together and a small
molecule such as H2O or HCl is eliminated.
An example is the formation of an ester.
Coupling reaction
The reaction between a diazonium ion and another aromatic
compound to form an azo compound, R-N=N-R’
Used to make azo dyes.
Dehydration
A term sometimes used to describe the elimination of a water
molecule from an alcohol to form an alkene.
Diazotisation
The formation of a diazonium salt from an aromatic amine.
Electrophile



Electrophilic addition
Typical of alkenes.
Electrophilic
substitution
Elimination
Typical of arenes since delocalisation is retained.
Esterification
A rection in which an ester is formed from an alcohol and a
carboxylic acid.
Positive ion or molecule with +
Attracted to an electron rich centre
Accepts a pair of electrons to make a dative covalent bond.
The loss of atoms or groups of atoms to produce an unsaturated
compound.
Typical of 1ry and 2ry alcohols.
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37
Friedel Crafts
acylation
The introduction of an acyl group, RCO-, into a benzene ring.
Named after it’s discoverers.
Friedel Crafts
alkylation
The introduction of an alkyl group into a benzene ring.
Named after it’s discoverers.
Hydrogenation
The addition of hydrogen atoms across a C=C.
Hydrolysis
A bond breaking reaction involving water, often catalysed by dilute
acid or alkali.
Typical of esters, amides and nitriles (R-CN).
Nucleophile



Nucleophilic addition
Typical of aldehydes and ketones.
Nucleophilic
substitution
Oxidation
Typical of halogenoalkanes.
Radical
Atom or molecule with an unpaired electron. These are very
reactive.
Radical substitution
Typical of alkanes.
Reduction
 Loss of oxygen
 Gain of electrons
 Gain of hydrogen
 Decrease in oxidation number
Typical of alkenes, aldehydes and ketones.
A negative ion or a molecule with a lone pair of electrons
Attracted to a positive/electron deficient centre
Donates a pair of electrons to form a dative covalent bond.
 Gain of oxygen
 Loss of electrons
 Loss of hydrogen
 Increase in oxidation number
Typical of 1ry alcohols, 2ry alcohols and aldehydes.
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