Haloalkanes Flashcards
what can haloalkanes by attacked by and why
Carbon is electron deficient (Cδ+) so are susceptible to attack by nucleophiles
property of C-halogen bond and why
C-Halogen bond is polar due to differences in electronegativity.
nucleophile definition
electron pair donor
examples of nucleophiles
Negatively charged ions e.g. OH-, Cl-, CN-
Molecules containing a lone pair of electrons e.g. H2O, NH3
mechanism for haloalkanes and OH-
product, reagent, condition
nucleophilic substitution
haloalkane -> alcohol
Reagent: NaOH or KOH (OH- nucleophile)
Conditions: heat under reflux, hot aqueous alkali solution
mechanism for haloalkanes and CN-
product, reagent, condition
why is this mechanism useful
nucleophilic substitution
haloalkane -> nitrile
Reagent: NaCN or KCN
Conditions: reflux in aqueous and alcoholic solvent
allows length of the carbon chain to be increased
mechanism for haloalkanes and NH3
product, reagent, condition
what does the ammonia act as
how can we minimise further substitution
nucleophilic substitution
haloalkane -> amine
Reagent: excess concentrated ammonia
Conditions: warmed in a sealed container
one NH3 acts as a nucleophile, the other as a base
excess ammonia
factors affecting rate of nucleophilic substitution (2) which overrules the other
More polar C-X bonds the more electron deficient Cδ+ will be so more susceptible to attack by nucleophiles so faster rate
Stronger C-X bonds are more difficult to break (shorter bonds are stronger) so slower rate
Most important factor so strength > polarity
elimination
removal of a small molecule from a compound
other mechanism with haloalkanes with OH-
product, reagent, conditions
elimination
haloalkane -> alkene
Reagent: concentrated OH- soluble salt e.g. NaOH, KOH (OH- base)
Conditions: hot ethanoic solvent
