M4 Chapter 15 - Haloalkanes Flashcards
What are haloalkanes?
Saturated organic compounds that contain carbon atoms and at least one halogen atoms.
Are haloalkanes soluble in water?
Insoluble as C-H bonds are non-polar and this is not compensated for enough by the C-X bond polarity.
Do haloalkanes have a polar bond? Why?
Yes, the halogen has a higher electronegativity than the C.
(Halogen = delta - and Carbon = delta +)
What type of intermolecular forces do they have? Why?
Permanent dipole-dipole and also induced (Ie: London aswell)
Because C-X polarity can create permanent dipoles.
How would haloalkanes have higher boiling points?
Increasing Carbon chain length
Halogen is further down group 7 (greater molar mass)
How would the mass of haloalkanes compare with the mass of an alkane of the same chain length?
The mass of the haloalkane would be greater due to the halogen mass being greater than hydrogen.
What is the most important factor in determining halogen reactivity?
Strength of the Carbon Halogen bond.
What would bond polarity suggest the order of reactivity would be?
C-F would be the most reactive as it is 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
What is a primary halogen?
The halogen atom is present at the end of the Carbon chain.
Define nucleophile.
Electron pair donor.
Give 3 examples of nucleophiles.
:OH-
H2O:
:NH3
What is nucleophillic substitution?
A reaction where a nucleophile donates a lone pair of electrons to f+ Carbon atom, f- atom then leaves the molecule as it is replaced by nucleophiles. (Substitution)
What is hydrolysis?
The splitting of a molecule via the use of water as a reactant.
What reactant often produces hydroxide ions for hydrolysis?
Water
What fission does water undergo to produce OH-?
Heterolytic Fission
Draw the mechanism for the reaction of bromoethane with NaOH.
refer to goodnotes (arrows in tho)
How can we test the rate of hydrolysis for the main 3 haloalkanes?
With water in the presence of aqueous silver nitrate.
We also need ethanol to ensure the haloalkanes dissolve to be able to react with the water nucleophile.
This uses nucleophillic substitution as the water here acts as a nucleophile.
What are the results of the test for rates of hydrolysis of the haloalkanes?
Chlorobutane = White precipitate forming slowly
Bromobutane = Cream Precipitate
Iodobutane = Yellow Precipitate forming rapidly
What are CFCs?
Chlorine-Fluoro-Carbons. These are haloalkanes containing C,F and Cl only (no H at all)
What constitutes the Ozone, includes reactions.
Ozone is continually being formed and broken down by the action of high energy UV.
O2 –> 2O (this is initiation)
2O + O2 <–> O3 (Propagation)
This is a reversible reaction which is stable ie in equilibrium.
This equilibrium is disturbed by CFCs.
What is the problem with CFCs then?
Although unreactive under normal conditions, 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.
Does ozone play a protection role in all layers of the atmosphere?
No, in the troposphere it contributes towards photochemical smog.
