Download TYPES OF ORGANIC CHEMICAL REACTIONS

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Substitution
Addition
Condensation/elimination
Hydrolysis
Mild oxidation & strong oxidation
Combustion
Acid/base reactions
A substitution reaction occurs whenever one
atom of an organic molecule is replaced by
another.
Substitution reactions often require heat
and/or a catalyst in order to occur.
Example:
Substitution of an alkane
H
H
H C H + Cl2
H C Cl + HCl
H
H
HEAT

Due to the strong bonding arrangement between the carbon atoms
in a benzene ring, the ring cannot be easily broken during
chemical changes. The hydrogen atoms that are bonded to each
carbon can be substituted for other atoms and groups.
Examples:
H
Br
+ Br2

FeBr 3..catalyst
+ HNO3

H 2 SO 4
TNT synthesis…
+
NO2 +
HBr
H 2O


In addition reactions, new atoms or groups
are bonded to the atoms of an organic
molecule. The organic molecule must be
unsaturated to start with (double or triple
I’m now ready
bonds!)
maketo
more
New bonds can be to
made
the carbon
bonds!
atoms involved in the
double or triple bond
if the
part of the bond is first broken.
H
CH2=CH2

breakpibond
C
H
H
C
H
H
H
+ H2 
C=C
H
H
H
H
C=C
H
H
+ H2O 
C=C
H
H
(a.k.a. “hydrogenation”)
H H
+ HCl  H-C-C-Cl
HH
H
H
H H
H-C-C-H
HH
H H
H-C-C-OH (a.k.a. “hydrolysis”)
HH

If the double or triple bond is part of a
molecule with three or more carbon atoms
in the chain, the most likely addition
reaction products can be predicted using a
rule first formulated by the Russian chemist
V.V. Markovnikov.
Markovnikov’s Rule
…the more electronegative atom will
predominantly bond to the carbon atom of
the double bond that has fewer hydrogen
atoms.
Eg.1
H
C=C-CH3
H
H
+ H2O 
H OH
H- C - C- CH3
H H
It should be mentioned that the primary
alcohol (1-propanol) is also a possibility, but
it would be produced in a much lower
proportion than the 2-propanol shown
above.
Eg.2
H-C  C-CH2-CH3
H
+ 2HCl 
Most favoured product!
Cl
H-C - C-CH2-CH3
H Cl

Organic compounds containing hydroxyl or
carboxyl groups can combine by
eliminating a molecule of water between
them.
An ether is created!
Example 1- condensation of two alcohols
H H
H-C - C-O-H
H H
H H
H H H H
2 SO 4
+ H-O-C - C-H H
 H-C - C-O-C–C-H
H H
H H
H H
+
H2O
Molecule of H O is formed
2

When an alcohol reacts with a carboxylic
acid to eliminate a molecule of water
between them, the resulting bond creates
an ester linkage as shown below:
We’ve created an ester
O
H H
H-C - C-O-H + H-O-C – CH2-CH3
O
H H
If excess
water
is
CH2-CH
2- O- C-CH2-CH3
added to an ester,
+ the
reaction will reverse
H2O
itself.
Demo!
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Esters often have characteristic flavours and
aromas which allows them to be used in
food products.
Methanol + butanoic acid  methyl butanoate (apples)
Octanol + acetic acid  octyl acetate (orange)
Benzyl alcohol + butanoic acid  phenyl butanoate (flowers)
Pentanol + acetic acid  pentyl acetate
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If a molecule of water is eliminated from
within a single molecule, an unsaturated
compound is formed and the molecule is
said to be “dehydrated.”
H
H
H
OH
H
H

H 2 SO 4
+ H2O
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In the terminology of organic chemistry,
when a molecule is oxidized, the number
bonds to oxygen atoms increases within the
molecule.
Oxidizing agents are varied: CrO3/H+,
KMnO4, K2Cr2O7
Often, the oxidizing agent is represented
simply as “O” over the reaction arrow:


O
Mild Oxidation
alcohol
..O
mild

 aldehyde
H
O
mild ..O
CH3-C-OH  CH3-C-H
H
ethanal
ethanol
Strong Oxidation
alcohol
H
CH3-C-OH
H

 Carboxylic acid
strong ..O


strong ..O
O
CH3-C-OH
Ethanoic acid
Strong Oxidation cont’d…
 Secondary alcohols require a strong oxidizing
agent and can only be oxidized to ketones.
OH
CH3-C-CH2-CH3
H
2-butanol


strong ..O
O
CH3-C-CH2-CH3
butanone
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All organic compounds can be combusted
or burned. Carbon dioxide gas and water
vapour are the products of hydrocarbon
combustion.
Combustion is really a type of very extreme
oxidation reaction where O2(g) is the
BOOM!
oxidizing agent.
2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O(g)
CH3-CH2-OH(l) + 3O2(g)  2CO2(g) + 3H2O(g)