Haloalkanes Flashcards
What elements do haloalkanes contain?
Carbon, hydrogen and at least one halogen.
Which order do you list the halogens in the haloalkane?
In alphabetical order.
Out of halogen and carbon atoms, which are more electronegative? What does this mean?
The halogen are more electronegative than carbon atoms. The electron pair is therefore closer to the halogen atom than the carbon atom. The carbon-halogen bond is therefore polar.
What is the definition of a nucleofile? Give an example
An atom or group of atoms that donate a pair of electrons to form a new covalent bond. An example is hydroxide ions, water molecules and ammonia molecules.
What happens in a nucleophilic substitution reaction?
The nucleophile replaces the halogen in a substitution reaction. A new compound is produced containing a different functional group.
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.
What happens in the hydrolysis of a haloalkane? Include a mechanicm diagram in your answer.
The halogen atom is replaced by an -OH group
How can you form a haloalkane form an alcohol? What is the other product?
Use a hydrogen halide. A substituation reaction will occur to produce a molecule of water.
How can you form a haloalkane from an alkene? What type of reaction is this?
Add a hydrogen halide at room temperature. This is an electrophilic substitution reaction.
How can you form a haloalkane from an alkane? Whta type of reaction is this?
Add chlorine under UV light. This is a ncleophilic substitution reaction.
What is the bond polarity of carbon to halogen bonds?
C d+ and Cl/Br/F d-
Why can H2O and OH- act as nucleophiles?
H2O contains a lone pair of electrons and OH- has a single lone electron.
Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if chlorine is present?
White
Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if bromine is present?
Cream
Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if iodine is present?
Yellow
What is the trend in reactivity as group seven is decended.
The reactivity increases as the group is decended.
Fill in the gaps. As Group 7 is _______, the size of the halogen atom _______ so the carbon to halogen bond length _______. This results in the carbon to halogen bond _______ decreasing which means it is _______ to break the bond.
As Group 7 is decended, the size of the halogen atom increases so the carbon to halogen bond length increases. This results in the carbon to halogen bond enthalpy decreasing which means it is easier to break the bond.
How does electronegativity change as you go down group 7?
Electronegativity decreases as you go down the group.
What conditions are required for the nucleophilic substitution of chloroethane and sodium hydroxide?
Reflux
What conditions are required for the nucleophilic substitution of chloroethane and water?
Reflux and an ethanol solvent.
What does CFC stand for?
Chlorofluorocarbon
Give an example of a CFC.
Trichlorofluoromethane
State 4 previous major uses of CFCs.
1) fridges
2) propellant for aerosols
3) air conditioning
4) packaging
State three properties of CFCs that make them ideal for their applications to real life.
They are volatile, unreactive and non toxic to humans.
Which bond is most likely to be broken in CClF3?
C-Cl
What general name do we give to the highly reactive species formed by homolitic bond fission?
Radicals
What health issues can be caused by exposure to UV radiation?
Skin cancer, eye cataracts and a weakened immune system.
What happens to ozone (O3) when it is exposed to UV radiation?
What is the Montreal Protocol?
A piece of legislation signed by lots of major countries on the prevention of CFCs
Why did ozone levels continue to drop after the introduction of the Montreal Protocol?
Because there were still CFCs and Cl· in the atmosphere.
In what year is the ozone predicted to have made a full recovery?
Between 2060 and 2070.
Write equations to show the formation and destruction of ozone in the stratosphere.
O2→2O•
O• + O2 → O3
O3 → O• + O2
How are Cl• formed from CFCs? Use CCl3F in your equation
CCl3F → CCl2F + Cl•
How does Cl• react with an O3 molecule?
Cl•
Give the reaction between Nitrogen and Oxygen to give NO•
Why do these reactions require high temperatures to take place?
N2 + O2 → 2NO•
Because they have high bond enthalpies.
Which peak on a mass spectrometry print out is the base peak? What does this mean?
The highest peak which is the most likely to form.
Which peak on a mass spectrometry print out is the molecular ion peak?
The peak that is the furthest to the right.
True or false? Only the negative ions are detected by the mass spectrometer.
False. Only positive ions are detected in the mass spectrometer.
