A-LEVEL CHEMISTRY: 3.3.3: Halogenoalkanes (ChemRevise) Flashcards
Halogenoalkanes:
Halogenoalkanes are Alkanes with a Halogen Functional Group (eg C-Cl, C-Br, C-I)
Halogenoalkanes can be classified as…
what does it depend on?
Primary, Secondary, Tertiary
depending on the number of Carbon Atoms attached to the C-Halogen Functional Group
Primary Halogenoalkane:
one carbon attached to the C-Halogen functional group
Secondary Halogenoalkane:
two carbons attached to the C-Halogen functional group
Tertiary Halogenoalkane:
three carbons attached to the C-Halogen functional group
Halogenoalkanes undergo either ___ or ___ reactions.
Substitution, Elimination
Organic reactions are classified by their…
Mechanisms
Nucleophilic Substitution…
swapping a Halogen atom for another atom or group of atoms.
Nucleophile:
electron pair doner
:Nu represents any ___. they always have a ___ ___, & act as…
Nucleophile, Lone Pair, electron pair doner
Hydrolysis:
Hydrolysis is defined as the splitting of a molecule (in this case a halogenoalkane) by a reaction with Water
Aqueous silver nitrate is added to a halogenoalkane. the halide leaving group combines with a silver ion to form a…
silver halide precipitate
how is a Silver Halide Precipitate formed?
Aqueous silver nitrate is added to a halogenoalkane. the halide leaving group combines with a silver ion to form a Silver Halide Precipitate.
the faster the Aqueous Silver Nitrate Precipitate is formed, the faster the ___ reaction, & the more ___ the halogenoalkane.
Substitution, Reactive
colour of AgI precipitate:
yellow
colour of AgBr precipitate:
cream
colour of AgCl precipitate:
white
Nucleophilic Substitution with aqueous hydroxide ions involves a change in functional group, from ___ to ___.
halogenoalkane, alcohol
Conditions for Nucleophilic Substitution with aqueous hydroxide ions:
in aqueous solution, warm.
what happens in Nucleophilic Substitution with aqueous hydroxide ions when the solvent is changed to ethanol?
an elimination reaction occurs
Elimination:
removal of small molecule (often water) from the organic molecule
Primary halogenoalkanes tend towards…
substitution
Tertiary halogenoalkanes tend towards…
elimination
Chloroalkanes & chlorofluoroalkanes can be used as…
solvents
Many of the uses of halogenoalkanes (eg in fridges) have now been stopped. why?
due to toxicity to the atmosphere
naturally occurring ozone layer:
O3
Ozone in the lower atmosphere is a ___ & contributes towards the formation of…
pollutant, smog
man-made ___ caused a hole to form in the ozone layer.
Chlorofluorocarbons (CFC’s)
Chlorine ___ are formed in the upper atmosphere when energy from ___ ___ causes C-Cl bonds in CFCs to break.
radicals, UV Light
Chlorine free radical atoms ___ the decomposition of ozone.
catalyse
the C-F bond is ___ than the C-Cl bond, & is not affected by…
stronger, UV light
