halogenoalkanes Flashcards
describe a nucleophile
nucleophile – they
always have a lone pair and act as
electron pair donator
The nucleophiles
attack the positive
carbon atom
We use curly arrows in mechanisms (with
two line heads) to show the movement of
two electrons
describe nucleophyllic reaction of aqueous hydroxide ions
the reaction causes the Change in functional group: halogenoalkane to alcohol
Reagent: potassium (or sodium) hydroxide
Conditions: In aqueous solution; Heat under reflux
the effect of CFCs
Man-made chlorofluorocarbons (CFC’s) caused a hole to form in the ozone
layer.
the effects of chlorine radical on ozonen
The chlorine free radical atoms catalyse the decomposition of ozone, due to these reactions,
because they are regenerated.
the free radical substitution for ozone
Cl . + O3 —> ClO. +02
what are the uses of halogenoalkanes
used as solvents.
Uses of Halogenoalkanes
Halogenoalkanes have also been
used as refrigerants, pesticides
and aerosol propellant
what is ozone
Ozone in the lower atmosphere
is a pollutant and contributes
towards the formation of smog.
how are chlorine radicals formed
Chlorine radicals are formed in the upper atmosphere when energy from ultra-violet radiation causes C–Cl bonds in chlorofluorocarbons (CFCs) to
break.
where are HFCS and why are they safer
HFCs (Hydro fluoro carbons) e.g. CH2FCF3 are now used for refrigerators
and air-conditioners. These are safer
as they do not contain the C-Cl bond
what effects the rate of substitution reactions
The rate of these substitution reactions depends on the strength
of the C-X bond
The weaker the bond, the easier it is to break and the faster the reaction
what is used to test the reactivity of halogenoalkanes
silver nitrate
what causes the precipitate to form in a halogenoalkane reaction
The precipitate only forms when the halide ion has left the
halogenoalkane and so the rate of formation of the precipitate
can be used to compare the reactivity of the different
halogenoalkanes.
