Halogenoalkanes & Modern Analytical Techniques Flashcards
Nucleophile definition
An electron pair donor
What type of reaction is the hydrolysis of halogenoalkanes?
A substitution reaction
Describe and explain the rate of hydrolysis of the halogenoalkanes
Rate of hydrolysis increases down the group. This is because the carbon-iodine bond is the weakest, and so is most easily broken
Describe an experiment that can be carried out to determine the rates of hydrolysis of the halogenoalkanes
Measure each halogenoalkane into a separate test tube, which is then placed in a water bath at 50*C
A test tube filled with a solution of ethanol, water and aqueous silver nitrate is placed in the same water bath
Once all the tubes have reached the same temperature, add equal volumes of the mixture to each halogenoalkane
Time how long it takes for each precipitate to form
Eg: CH3CH2Cl + H2O –> CH3CH2OH + H+ + Cl-
Ag+ + Cl- –> AgCl
Explain how PTFE is made and it’s uses
Poly(tetrafluoroethene) is made from the polymerisation of tetrafluoroethene
Carbon-fluorine bonds are very strong, so PTFE is inert and resistant to chemical attack. It is also heat resistant, so is used for coating pans or metal surfaces to prevent chemical attack
Explain how PVC is made and it’s uses
Poly(vinyl chloride) is made from the polymerisation of chloroethene
It is used as drainpipes, plastic window frames and packaging
What were CFCs originally developed for?
For use as aerosols, refrigerants and in air conditioning because of their low reactivity, high volatility and non-toxicity
What is the problem with CFCs?
They have caused environmental damage to the ozone layer. The ozone layer absorbs harmful UV radiation. Depletion of the ozone allows harmful radiation to reach the lower atmosphere, which can cause skin cancer
Alternatives to CFCs and their advantages and disadvantages
HCFCs
These are biodegradable, non-flammable and non-toxic
However they still deplete the ozone layer by a small amount
What sort of radiation do molecules absorb and what effect does this radiation have on the molecules?
All molecules absorb infrared radiation, which causes covalent bonds to vibrate
What can infrared spectroscopy be used for?
In breathalysers to measure ethanol in the breath, to monitor air pollution
How can mass spectrometry be used to determine the molecular mass of a molecule?
The molecular ion peak indicates the molecular mass of an atom
What can mass spectrometry be used for?
For monitoring levels of environmental pollution, such as lead, and in the Mars space probe
Explain how a mass spectrum would show the presence of a particular element
M/z peaks at around its Mr
Outline how a mass spectrum would show how many different isotopes of an element there were in a specific place
The number of m/z peaks
