C15 - Haloalkanes Flashcards
What is Hydrolysis?
A chemical reaction involving water or an aqueous solution of a hydroxide that causes the breaking of a bond in a molecule. This results in a molecule being split into two products.
What is the result of hydrolysis?
The molecule being split into two products.
What are CFC’s?
Chlorofluorocarbons molecules which contain only chlorine, fluorine and carbon.
What are some benefits of CFC’s?
They are very stable, volatile, non-flammable and non-toxic.
What does volatile mean?
A substance easily evaporated at normal temperatures.
What is the Ozone?
Ozone (O3) in the upper atmosphere which absorbs ultraviolet radiation.
What are the dangers of ultraviolet radiation?
Causes sun burn and skin cancer.
How is the ozone formed?
When oxygen molecules (O2) is broken into two oxygen radicals by ultraviolet radiation. The oxygen radicals react with oxygen molecules to form O3, which is the Ozone.
How do CFC’s form holes in the atmosphere?
CFC’s in the upper atmosphere absorb UV radiation and split to form chlorine (halogen) free radicals. These free radicals catalyse the destruction of ozone, destroying ozone molecules and are then regenerated to destroy more.
Explain the break down process for the ozone layer and CFC’s with equations.
- CF2Cl2 —> · CF2Cl + Cl ·
Chlorine free radicals are formed when the C-Cl bonds in CFC’s are broken by ultraviolet radiation. - Cl · + O3 —> O2 + ClO ·
ClO · + O —> O2 + Cl ·
These free radicals are catalysts. They react with the ozone to form an immediate ClO · and oxygen molecules.
The O radical comes from the breakdown of oxygen by ultraviolet radiation.
The Chlorine free radical is regenerated and attacks another ozone molecule again.
Why are CFC’s stable?
Because of the strength of the carbon-halogen bonds.
So what is the overall reaction for radical (chlorine and other radicals)breaking down the ozone?
O3 + O —> 2 O2 and Cl · / other radicals is the catalyst.
What is another free radical (other than chlorine) which breaks down the ozone?
Nitrogen Oxides (NO ·)
How is nitrogen oxides produced?
Car and Aircraft engines, thunderstorms.
How do NO · free radicals affect the ozone?
The same way as chlorine radicals.
What is the universal reaction equations for radical and the ozone for it to break down?
Let the radical be R
R + O3 —> RO + O2
RO + O —> R + O2
Overall Reaction - O3 + O —> 2 O2
What did scientific evidence for CFC’s ozone depletion cause?
Government legislation against CFC use.
Why do C-Cl bonds in CFC’s only create free radicals instead of C-F or C-H bonds?
C-F and C-H bonds are too strong to be broken by UV light. C-Cl bonds are weak enough to broken by UV Radiation.
What alternatives uses instead for CFC’s?
HFC’s - don’t contain chlorine so don’t effect the ozone.
HCFC’s - still effect the ozone but much less then CFC’s.
Carbon Dioxide and Ammonia - used instead of nitrogen in aerosols.
What are Haloalkanes?
An Alkane with at least one halogen atom in place of a hydrogen atom.