2. SUBSTITUTION REACTIONS
Substitution Reactions
Reactions where an atom or side-chain is
replaced by a different atom or side-chain.
H3C-X + H2O CH3OH + HX
X
+ X2 + HX
3. SUBSTITUTION REACTIONS
Substitution Reactions
Identify the substitution reaction(s):
a) Heat
+ Br2 Br + HBr
UV
Substitution
b) FeBr3
+ Br2 Br + HBr
Br Substitution
Room
c) temperature
+ Br2 Br
Halogenation
4. SUBSTITUTION REACTIONS
Substitution Reactions
Nitric acid may react with benzene to
substitute an H with a –NO2 (nitro) group.
H2SO4
+ HNO3 NO2 + H2O
5. SUBSTITUTION REACTIONS
Substitution Reactions
Alkyl groups may also be added to benzene
groups.
AlCl3
+ CH3CH2Cl CH2CH3 + HCl
6. SUBSTITUTION REACTIONS
Example #1
Predict the product formed when benzene
reacts with chloromethane in the presence
of AlCl3 catalyst.
AlCl3
+ CH3Cl CH3 + HCl
7. SUBSTITUTION REACTIONS
Substitution Reactions
At first, only a single H group will be
substituted in any reaction involving a
cyclic or aromatic hydrocarbon.
Additional substitutions on an aromatic ring
will have preferences for location.
8. SUBSTITUTION REACTIONS
Second Aromatic Substitution
When another group is added to an
aromatic ring, rules determine the
preferred location of the second
group.
Br + Br2
Br Br
Br Br Br Br
ortho meta para
12. SUBSTITUTION REACTIONS
In the case of NH2 as a substituent, ortho and para are favoured
because of the stability of the reaction intermediate:
4 resonance
structures
3 resonance
structures
4 resonance
structures
14. SUBSTITUTION REACTIONS
Amines are prepared by reacting alkyl
halides with NH3.
CH3CH2-I + NH3 CH3CH2-NH2 + HI
2° and 3° amines are produced with the
addition of more alkyl halide reactants.
Homework:
p30 #4, 6
p31 #1- 3a-c
16. ELIMINATION REACTIONS
Two adjacent atoms or side groups are
removed resulting in a double bond.
Conc.
H2SO4
CH3CHOHCH3 CH3CH=CH2 + H2O
The reverse reaction is an addition reaction.
Homework:
p44 #7,8