Download CI 12.4 - Sackville School

Medicines by Design
Revision of reagents, conditions and reaction
types:





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
O
9
C
R
OH
R
O
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
C
NH2

CH3
O
R
Cl
Dil H2SO4
Heat + reflux
3
6
C
NaCN in ethanol/H2O
Heat + reflux
R
C
OH
9
H
7
CH2
COOH

C
NH
R'

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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
R'
O
C
R
Cl
C
NH2
O
R
R
CH3
R
CH2
NH2
R
CH2
COOH
C
NH
R'

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reagents and conditions
A11. Aliphatic reagents and conditions
X11
H
C
Al2O3
300oC
R
C
H
CH2
H
O
O
O
C
R
OH
R’OH/conc. H2SO4 cat
heat + reflux
H
C
R
OH
Conc.
HBr
room
temp
SCl2O
heat + reflux
NaOH(aq)
heat + reflux
NaBr(s) + conc. H2SO4
heat + reflux
NaBH4
room temp
Dil. HCl or H2SO4 or
NaOH
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
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
CH2
COOH

C
NH
R'

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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
C
NH
C
NH2

R
R'
R'

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Key words and
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A14. Aliphatic reaction types
Esterification or
condensation
X14
R
H
C
Elimination
or dehydration
R
C
H
CH2
Oxidation
O
O
C
R
OH
R
C
H
R
OH
Reduction
H
Addition or
R
Br
CH2
CN
R
Nucleophilic
substitution or
acylation
C
NH2

O
R
R
CH3
R
CH2
NH2
R
C
Nucleophilic
Substitution or
acylation
Hydrolysis
Radical
substitution
R'
O
R
Cl
Nucleophilic
substitution
Nucleophilic
substitution
hydrogenation
CH2
O
Nucleophilic
substitution or
acylation
O
R
C
Hydrolysis
Nucleophilic
substitution
Nucleophilic
substitution
Electrophilic
addition
O
Oxidation
CH2
COOH

C
NH
R'

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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=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
C
(reagent) is Br2(g) or Br2(l) or Br2 in an organic solvent
(N.B. Salters includes catalysts in this category if required)
(conditions) are room temperature
(N.B. Salters includes pressures here if required)
b. Ethene with bromine water Br2(aq)
H H
H2C CH2 (g)
+
Br2 (aq)
+
H2O(l)
H C C H (l)
+
HBr(aq)
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
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
150°C and 5 atm with the Ni (or room temp. and pressure with the Pt)
N.B. Pt is white gold: very expensive!
e. Ethene with water H2O(g) (it is steam at 300°C)
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
300°C 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
The mechanism of the electrophilic addition reaction between
bromine and alkenes
curly arrows
CI 12.2
show movement of
a pair of electrons
Mechanism for reaction in (a) above:
H
H
H
C
= C
H
H
H
C
+
C
H
+
-
Br :
H
Br
a carbocation and a bromide ion
+
Br δ
Br δ




The bromine molecule is polarised i.e it has a δ+ and a δ- atom like when the bond is
polar. This happens because the electrons in the Br 2 molecule are repelled by the
electrons in the C=C.
The Brδ+ 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.
N.B. ‘philic’ means ‘to like’ and ‘phobic’ means ‘to hate’.
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 and is now a C
atom with one less electron so it has a single positive charge.

The bromide ion is written:



One of the lone pairs has come from the bond in the Br 2 molecule.
It had a share of the bonding pair but now has both electrons.
It now has overall gained an electron so the Br atom now has a negative charge.
Br
Then we have the next step:
H
H
+
C
C
H
H
H
H
C
C
Br
Br
H
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.
Back to map
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
What are the alternative reagents and conditions for
this reaction?
Reagents: ethanol passed over alumina
(Al2O3) catalyst;
Conditions: 300oC;
N.B. 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 two 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
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
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
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 two common nucleophiles:
Formula
OH -
Structure
[inc. lone pairs]
_ ..
:O:H
..
Reaction
Organic product
R-X + OH-  R-OH + X-
NH3
alcohol
amine
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
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, p303 may help)
R
NaBr(s) and concentrated H2SO4
C
heat and reflux
Back to map
H2O
A6. Amines can act as nucleophiles with acyl chlorides
CI 13.8
Ammonia/amines react with acyl chlorides:
ammonia
+
acyl chloride
primary amine
+
primary amide
acyl chloride
+
secondary amide
HX
+
HX
These are nucleophilic substitution reactions.
Complete the following equations:
O
+
H N H
Cl
H
C
+
CH3
an acylchloride
ammonia
primary amide
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
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
methyl methanoate
H
H
H
C
C
O
H C OH
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
Examples:
acid
+
alcohol

ester
H 3C
+
C
H
+
H
OH
H 3C
+
C
H
H
OH
C
C
OH
ethanoic acid
CH3
H
water
H3C
+
C
O
H
O
H
H
H
C
C
C
H
H
CH2CH3
water
ethyl ethanoate
H
H
H
O
ethanol
O
O
+
C
methyl ethanoate
H
H
ethanoic acid
c.
H3C
OH
methanol
O
C
C
H
ethanoic acid
H 3C
O
O
OH
b.
water
H
O
a.
+
O
OH
H3C
H
propanol
+
C
O
CH2CH2CH3
O
H
H
water
propyl ethanoate
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 Activity 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
C CH3
carboxylic acid
O C CH3
ester
+
+
water
(conc. H2SO4 catalyst and heat under reflux is needed even with an alcohol)
Back to map
H2O
Method 2
O
OH
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
+
+
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
HCl
A8. The hydrolysis of esters
CI 13.5
The reverse of esterification is hydrolysis. Hydrolysis is bond breaking involving water:
O
H 3C
+
C
O
O
H
H
H
C
C
H
H
H
CH2CH3
ethyl ethanoate
H
water
ethanol
O
OH
+
H3C
C
OH
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?
Back to map
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
Aldehydes are made when a primary alcohol is oxidised.
Examples:
[2 C’s → eth; suffix -al]
H O
H C C
23
24
H
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.
Examples:
O
H3C
C
41
CH3
propanone
H
H
C
44
H
C
45
H
O
C
C
46
47
H
H
H
pentan-2-one
H
C
48
H
H
The carbonyl group is midway along the
carbon chain. A number may be
required to show which C atom has the
carbonyl group.
Formation of aldehydes and ketones from alcohols:
Remember a triangle!
primary alcohol
secondary alcohol
oxidation
aldehyde
oxidation
oxidation
carboxylic acid
aldehyde
tertiary alcohol
A good oxidising agent is acidified potassium dichromate (VI) solution.
Back to map
Here is the half equation showing what happens to the dichromate ions:
Cr2O72- + 14H+ + 6e-  2Cr3+ + 7H2O
Oxidation numbers: +6 (acid) → +3
Colour change: 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?
Back to map
A closer look at the reaction of the primary alcohol:
H
H
H
C
C
H
H
H
H
OH
C
C
H
H
H
a
primary alcohol
H
O
C
O
C
OH
H
b
aldehyde
carboxylic acid
Why are both of these steps described as oxidation?
a.
b.
A closer look at the reaction of a secondary alcohol:
H
H
H
H
C
C
C
H
OH
H
secondary alcohol
H
H
H
H
C
C
C
H
O
H
ketone
Why doesn’t oxidation of the ketone occur?
H
H
H
C
C
H
O
OH
carboxylic acid
A closer look at the reaction of a 3ry alcohol:
H
H
C
H
H
H
H
C
C
C
H
OH
H
H
H
H
tertiary alcohol
H
C
C
C
H
O
H
H
ketone
Why doesn’t oxidation of a tertiary alcohol occur?
N.B. 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.
Back to map
Reduction of carbonyls to alcohols
Aldehyde  primary alcohol
Ketone  secondary alcohol
R = NaBH4(aq)
C = room temperature
Name the reagent:
Give the formulae of the carbonyl compounds 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


R7
H2(g), Ni catalyst,
300°C, 30 atm.
SO2OH

1
1
3.
2
NO2
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Sn + conc. HCl;
heat + reflux;
NH2
6
4
5
+
N
N Cl-
O
R
C
6
R
N
N
OH
Aromatic reagents and conditions


Cl
Br

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R8
Br2(l), FeBr3 cat.
room temp.
H2(g), Ni catalyst;
300°C, 30 atm.
SO2OH
conc. H2SO4.
heat + reflux
Cl2(g), AlCl3 cat.
room temp/ anhydrous
conc. HNO3, conc. H2SO4 cat.
<55°C
RCl(l), AlCl3 cat.
heat + reflux/ anhydrous
NO2
Sn + conc. HCl
heat + reflux
NH2
NaNO2(aq)/dil. HCl
<5°C
RCOCl(l), AlCl3 cat.
heat + reflux/ anhydrous
+
N
N Cl-
O
R
C
alkaline phenol
<5°C
R
N
N
OH
Aromatic reagents and conditions

Cl
Br

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R9
NO2
SO2OH
NH2
+
N
N Cl-
O
R
C
R
N
N
OH
Aromatic reaction types



Cl
Br

C10
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NO2
SO2OH
NH2
+
N
N Cl-
O
R
C
R
N
N
OH
Aromatic reaction types



Cl
Br
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C11
Electrophilic
substitution
Hydrogenation
SO2OH
Electrophilic
substitution
Electrophilic
Substitution or
Friedel Crafts alkylation
Electrophilic
substitution
Electrophilic
substitution
NO2
NH2
Reduction
Diazotisation
Electrophilic
Substitution or
Friedel Crafts acylation
+
N
N Cl-
O
R
C
R
Coupling
reaction
R1. Halogenation of the ring in arenes
CI 12.4
Electrophilic substitution . . .
The H+ reacts with the FeBr4-.
Step 1:
The bromine molecule is polarised as
it approaches the benzene ring.
+
Br +
Br
-
FeBr4-
Br
The FeBr3 helps to polarise the
bromine by accepting a lone pair of
electrons from one of the bromine
atoms.
FeBr3
The bromine molecule is so polarised
that it splits.
Step 2:
Br
Br+
FeBr4-
H
Why does the benzene attract electrophiles?
R
Br2(l) and either FeBr3 or Fe(s)
C
room temperature
E
C6H6 + Br2  C6H5Br + HBr
Br
FeBr3
Br+ becomes bonded to a ring C
and H+ is lost. Br+ is an
electrophile:
 has a +ve charge;
 attracted to electron rich
centre;
 accepts pair of electrons to
form a dative covalent bond;
FeBr3 is regenerated as it is a
catalyst in the reaction.
What would the formula of the product have been if addition had occurred rather than
substitution?
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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.
FeBr4The chlorine molecule is so polarised
that it splits.
FeBr
AlCl33
Step 2:
Br
Br+
FeBr4-
Cl+ becomes bonded to a ring C and
H+ is lost. Cl+ is an electrophile:
 has a +ve charge;
 attracted to electron rich centre;
 accepts pair of electrons to form a
dative covalent bond;
R
C
E
H
Br
The H+ reacts with the AlCl4-.
AlCl3 is regenerated as it is a
catalyst in the reaction.
Cl2(l) and AlCl3(s)
room temperature, anhydrous
C6H6 + Cl2  C6H5Cl + HCl
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FeBr3
R2. The nitration of benzene
CI 12.4
Electrophilic substitution . . .
R
Conc. nitric acid and conc. sulphuric acid as a catalyst
< 55°C; Explain why . . .
C
C6H6 + HNO3  C6H5NO2 + H2O
E
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?
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+ H2SO4
R3. The sulphonation of benzene
CI 12.4
Electrophilic substitution . . .
O
OH
S
E
+ H2SO4
R
Conc. sulphuric acid
C
Heat and reflux
O
+ H2O
Draw the structural formula of the electrophile and name it:
Name the organic product of this reaction:
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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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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
R
C
+
CH3 C
C
CH3
Cl
Give the reagents:
Give the conditions:
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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+ HCl
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 5°C?
Azo compounds:
This is an azo compound. Circle the azo group:
R
N
N
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R'
Cl- + 2H2O
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 two organic reagents above . . .
R = the phenol is in an alkaline solution for this reaction;
C = at a temperature less than 5°C 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:
Key Words
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OH + HCl
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 +ve
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



positive ion or molecule with +;
attracted to an electron rich centre;
accepts a pair of electrons to make a dative covalent
bond;
Electrophilic
addition
Typical of alkenes.
Electrophilic
substitution
Typical of arenes since delocalisation is retained.
Elimination
The loss of atoms or groups of atoms to produce an
unsaturated compound.
Typical of primary and secondary alcohols.
Esterification
A reaction in which an ester is formed from an alcohol and a
carboxylic acid.
Friedel Crafts
acylation
The introduction of an acyl group, RCO-, into a benzene ring.
Named after its discoverers.
Friedel Crafts
alkylation
The introduction of an alkyl group into a benzene ring.
Named after its discoverers.
Hydrogenation
The addition of hydrogen atoms across a C=C.
Hydrolysis
Nucleophile
A bond breaking reaction involving water often catalysed by
dilute acid or alkali.
Typical of esters, amides and nitriles (R-CN).



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;
Nucleophilic
addition
Typical of aldehydes and ketones.
Nucleophilic
substitution
Typical of halogenoalkanes.
Oxidation
Radical
Radical
substitution
Reduction
 gain of oxygen;
 loss of electrons;
 loss of hydrogen;
 increase in oxidation number;
Typical of primary alcohols, secondary alcohols and
aldehydes.
Atom or molecule with an unpaired electron. These are very
reactive.
Typical of alkanes.
 loss of oxygen;
 gain of electrons;
 gain of hydrogen;
 decrease in oxidation number;
Typical of alkenes, aldehydes and ketones.