Haloalkanes Flashcards
What are haloalkanes?
Organic compounds that contain carbon atoms and at least one halogen atom
Are haloalkanes soluble in water?
Insoluble as C-H bonds are non polar and not compensated enough by C-X polarity
What type of intermolecular forces do haloalkanes have?
London forces and permanent dipoles between C-X
When would haloalkanes have higher boiling points?
Increased carbon chain length or a halogen further down group 7
What is the most important factor in determining halogen reactivity?
The strength of carbon-halogen bond
What would bond polarity suggest the order of reactivity would be?
C-F would be most reactive as its the most polar bond
What would bond enthalpies suggest the order of reactivity would be?
C-I would be the most reactive as it has the lowest bond enthalpy
Define nucleophile
Electron pair donor
Give 3 examples of nucleophiles
:OH-
:CN-
:NH3
What is nucleophilic substitution?
A reaction where a nucleophile donates a lone pair of electrons
What is hydrolysis?
A reaction where water is a reactant that causes the breaking of a bond in a molecule (NaOH or KOH)
What fission does water undergo to produce OH-
Heterolytic fision
Why does the hydrolysis of 1-chlorobutane react the slowest?
Because the C-Cl- bond is the strongest
What are CFCs?
Haloalkanes containing C, F and Cl only
What is the problem with CFCs?
They catalyse the breakdown of ozone in the atmosphere via free radical substitution
What is the main function of the ozone layer?
Provides protection from harmful UV radiation
How does O3 form initially?
- Ozone has a delicate equilibrium
- Initially UV breaks O2 = O•
- O2 + O = O3
- Ozone rate of formation is the same as it breaks down
Why are CFCs very stable?
Because of the strength of the carbon-halogen bonds within their molecules
How do CFCs form radicals once it reaches the stratosphere?
UV radiation provides sufficient energy to break a carbon-halogen bond by homolytic fission, the Cl-Cl bond has the lowest enthalpy so is the bond that breaks
Draw the mechanism to show the depletion of Cl• to the ozone layer
Cl2 = 2Cl•
Cl• + O3 = ClO• + O2
ClO• + O = Cl• + O2
2Cl• = 2Cl2
