Download Combustion, Addition and Elimination Objective Combustion Example

Combustion, Addition and Elimination
lesson 8
chapter 14/15
Objective
You will be able to identify the types of
reactions that different organic molecules can
undergo.
Combustion
The rapid reaction with oxygen.
Complete combustion involves the burning (exothermic
reaction) of a hydrocarbon in excess oxygen. This will
produce carbon dioxide gas and water vapor.
Remember to balance these in the order CHO.
Example
1. Write the a balanced reaction for the complete
combustion of 2-methypentane.
2. Write the reaction for the combustion of pent-2-ene.
Addition Reactions
Unsaturated hydrocarbon are reacted.
Since the site of the double or triple carbon-carbon bond
is weaker than the single bond, this bond can break and
then we have free bonding electrons where another
element or functional group can be added.
In general:
Examples
Write the reaction, both structural and in a
chemical equation for each of the following.
Ethene reacts with chlorine gas.
Propene with iodine.
It may be possible to have more than one product from
a reaction.
Example:
but-1-ene + hydrogen fluoride.
Propene with water
But-1-yne reacts with excess hydrogen.
Testing for Unsaturated Compounds
Bromine is used to test for the presence of multiple
bonds.
Normally bromine is brownish liquid, when added to an
alkene or alkyne the color disappears.
When added to an alkane no change is detected.
Potassium permanganate has similar abilities, though it
is not as clear cut as bromine.
Elimination Reactions
This like the reverse of an addition reaction. Here atoms
are removed and a double bond is formed.
Alcohols and alkyl halides can undergo elimination
reactions.
General Reaction for alkyl halides is
Elimination in alkyl halides
These undergo elimination in the presence of strong
bases.
Example: 1-chloropropane is heated in the presence of
sodium methoxide.
Elimination in Alcohols
Alcohols undergo elimination in the presence of strong
acids.
General reaction is
HH
| |
H
acid H
+ HOH
H -C-C-OH ⟶ C=C
H
H
| |
HH
Example: butan-2-ol is heated in the presence of a
catalyst, sulfuric acid.
Assignment
Read 586-593
Do practice problems #1a-c,
2a,b,d, 4,6 p. 596