13.0 Halogenoalkanes Flashcards
(15 cards)
Label a C-Br bond to show the polarity and explain
why the bond is polar.
d+ — d-
The halogen is more electronegative than carbon so has a greater ability to draw the bonding pair of electrons towards its nucleus.
Define the terms ‘nucleophile’ and ‘substitution’.
Nucleophile – a species that donates a pair of electrons
Substitution – replace one group on a molecule with
another.
List the three common nucleophiles that react with
haloalkanes.
:OH-, :CN-, :NH3
Explain why haloalkanes only react readily when
dissolved in ethanol.
Haloalkanes cannot hydrogen bond, so are not soluble in water
What does a curly arrow represent in a reaction
mechanism?
Movement of a pair of electrons (in bond making or
breaking).
Explain why rate of reaction of haloalkanes increases as you go down the halogen group.
As you go down the halogen group, the C-X bond
strength decreases, reducing the energy required to
break the bond and increasing the rate.
Define a ‘hydrolysis’ reaction.
Splitting/breaking bonds with water.
Define an ‘elimination’ reaction.
Where two new product molecules form from one
reactant/a new molecule is removed from the original reactant.
Why does a hydroxide ion (:OH-) act as a base?
:OH- is a proton acceptor
What conditions are needed for :OH- to act as
a) a nucleophile
b) a base
a) Aqueous, warm
b) Ethanolic, heat/high temp
What role does ozone have in the atmosphere?
Absorbs UV light.
Write an equation to show the species formed when
CF3Cl (a CFC) is exposed to UV.
CF3Cl → ∙CF3 + ∙Cl
What are the key uses of CFCs.
Refrigerants, solvents.
Give the overall balanced equation for the
decomposition of ozone (O3) to oxygen (O2)
2 O3 → 3 O2
Give the balanced equations to show how chlorine
free radicals catalyse the decomposition of ozone.
Cl∙ + O3 → ClO∙ + O2
ClO∙ + O3 → Cl∙ + 2O2
