4.2.2 Haloalkanes
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What are haloalkanes?
Saturated organic compounds that contain carbon atoms and at least one halogen atom
Are halogenoalkanes soluble in water?
Insoluble as C-H bonds are non-polar, not compensated for enough by C-X bond polarity
Do halogenoalkanes have a polar bond? Why?
Yes polar, as halogen has a higher electronegativity than C (halogen is δ-, carbon is δ+
What type of intermolecular forces do they have? Why?
Permanent dipole-dipole and London forces of attraction C-X bond polarity creates permanent dipoles
When would halogenoalkanes have higher boiling points?
Increase carbon chain length Halogen further down group 7
What is the most important factor in determining halogen reactivity?
The strength of the carbon bond
What would bond polarity suggest the order of reactivity would be?
C-F would be most reactive as most popular bond
What would bond enthalpies suggest the order of reactivity would be?
C-I would be most reactive as lowest bond enthalpy
What is a primary halogen?
The halogen atom is present at the end of the chain
Define nucleophile
Electron pair donor
Give 3 examples of nucleophiles
:OH- :CN- :NH3-
What is nuclearphilic substitution
A reaction where a nucleophile donated a lone pair of electrons to δ+ C atom, δ- atom leaves molecule (replaced by nucleophile)
What is hydrolysis
A reaction when water is a reactant
What reactant often produces hydroxide ions for hydrolysis?
Water
What fission does water undergo to produce OH-?
Heterolytic fission
What are CFCs?
Chlorine-fluoro-carbons Haloalkanes containing C,F and Cl only (no H)
What is the problem with CFCs?
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.