Chemical Reactions of The Alkanes Flashcards
Why are alkanes not very reactive?
The sigma bonds are strong.
The C-C bonds are non-polar
The carbon and hydrogen bonds have electronegativities so similar that they are considered non-polar.
What do all alkanes react with to produce carbon dioxide and water?
A plentiful supply of oxygen.
Why are alkenes used as fuel?
They are available, easy to transport and burn without releasing toxic products.
What are the reactants in combustion?
An alkane and oxygen.
What are the products of combustion complete combustion?
Carbon dioxide and water.
What is the one thing that always has one mole in combustion?
The alkane.
What are the products of incomplete combustion?
CO, CO2, H2O, C
When does incomplete combustion occur?
When there is not enough oxygen.
What is required in order for alkanes to react with halogens?
UV light
Why is UV light needed in the reaction of alkanes with halogens?
To provide the initial energy for the reaction.
What type of reaction is the reaction of alkanes with alkenes?
Substitution
What is the mechanism for the bromination of alkanes called?
Radical substitution.
What are the three stages for radical substitution?
Initiation
Propagation
Termination
What happens in the initiation step?
The covalent bond in a bromine molecule is broken by homolytic fission.
What is formed in the initiation step?
Two bromine radicals.
Where does the energy for bond fission come from in initiation?
The UV light.
What happens in the propagation stage?
A chain reaction
How many equations are used to show propagation?
2
What should always be different when constructing a propagation equation?
The reactant radical should be different to the product radical.
What radical should be used for the second propagation equation?
The product radical from the first equation.
In theory, when does the propagation stage end?
When the products run out.
In practice, when does propagation end?
When two radicals collide.
What happens in the termination step?
The two radicals collide.
What is formed in the termination step?
A molecule with all electrons paired.
