Module 4- Haloalkanes Flashcards
What are haloalkanes?
Saturated organic compounds that
contain carbon atoms and at least one
halogen atoms
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 they have higher
boiling points?
Increase Carbon chain length
Halogen further down group 7
How would the mass of a
haloalkane compare with the
mass of an alkane of the same
chain length?
Greater as mass of halogen > mass of H
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 most polar 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 nucleophilic
substitution?
A reaction where a nucleophile donates
a lone pair of electrons to δ+ C atom, δ−
atom leaves molecule (replaced by
nucleophiles)
What is hydrolysis?
A reaction where water is 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 (aq)
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
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
How do CFCs break the ozone
layer down?
Free radical substitution
Write an equation for the
overall decomposition of
ozone into oxygen (O2
)
2O3→ 3O2
Write free radical substitution
equations to show how Cl free
radicals catalyse the
breakdown of O3
Cl2→ 2Cl* (in presence of UV light)
Cl* + O3→ ClO* + O2
ClO* + O3→ 2O2 + Cl*
Overall: 2O3→ 3O2
Write free radical substitution
equation to show how nitrogen
monoxide can decompose
ozone
NO + O3→ NO2+ O2
NO2 + O → NO + O2
Overall- O3 + O → 2O2
