10.2 Functional Group Chemistry Flashcards
(38 cards)
What reactions to alkanes undergo?
Combustion reactions.
What are the products of complete combustion?
Carbon dioxide and water.
What are the products of incomplete combustion?
Incomplete combustion is when there is a limited supply of oxygen and the reaction produces carbon monoxide, carbon and water.
Why are alkanes unreactive?
There are high strength C-C and C-H bonds.
The C-C and C-H bonds and the overall molecules are essentially non polar.
Whta is a substitution reaction?
One in which one atom or group is replaced by another atom or group.
What are free radicals?
Species (atoms or groups of atoms) with an unpaired electron.
What is homolytic fission?
Where a covalent bond breaks so that one electron goes back to each atom making up the original covalent bond.
How is homolytic fission shown?
With fish hook arrows showing the movement of one electron.
How to alkanes undergo substitution reactions?
In the presence of UV light alkanes undergo substitution reactions with halogens, the mechanism for these reactions is FREE RADICAL SUBSTITUTION.
What are the steps of free radical substitution for the reaction of methane with chlorine?
The first stage is photochemical homiletic fission of the bond between the halogen atoms to produce two free radical: INITIATION Cl2 ----> 2Cl* PROPOGATION Cl* + CH4 ----> CH3* + HCl PROPOGATION CH3* + Cl2 ---> CH3Cl + Cl* TERMINATION Cl* + Cl* ----> Cl2 TERMINATION Cl* + CH3* ----> CH3Cl TERMINATION H3C* + CH3* ----> C2H6
The Cl* generated in the second propagation step can go on to react further with another methane molecule so the the cycle of propagation sets starts again - a chain reaction.
Why are alkenes more reactive than alkanes?
Onw component (the pi bond) of the C=C is weaker than a normal C-C single bond. The double bond (four electrons) attracts electrophiles (reagents attracted to electrons).
What reactions to alkenes undergo?
Addition reactions.
What happens when alkenes react with halogens?
The double bond opens up and the halogens add on.
What happens when alkenes react with hydrogen?
With a nickel catalyst and 150 degrees Celsius heat, the double bond opens up and hydrogen adds on.
What happens when alkenes react with hydrogen and a halogen eg H-Br?
If heated the double bond opens up and they add on to the molecule.
What happens when alkenes react with water?
With a concentrated sulphuric acid catalyst and heat the double bond opens up and the water adds on.
How can alkenes and alkanes be distinguished form each other?
By shaking them with bromine water.
Alkenes will change from orange to colourless.
Alkanes there will be no change in colour.
What are the conditions needed for alkene to undergo addition polymerisation?
Require high temperature and pressure and maybe a catalyst.
What is the structure put in brackets called?
The repeating unit of the polymer, the basic unit form which the whole polymer can be made up.
How are addition polymers named?
According to the monomer from which they were made.
What is the only group that reacts when the polymerisation reaction occurs?
Only the C=C group reacts, all other groups attached to the C=C are unaffected.
How do you draw or find the repeating unit form part of the polymer chain?
Take any two adjacent Cs in the polymer chain to give the repeating unit.
How can you make the repeating unit the original monomer?
Put a double bond between the 2Cs.
How do alcohols combust in oxygen?
The produce water and carbon dioxide.
