Halogenoalkanes Flashcards
(20 cards)
what determines the reactivity of a halogenoalkane?
- polarity
- bond strength
what factor is most important in determining the reactivity of a haloalkane?
bond strength (trumps polarity of C-X bond)
which haloalkane bond is the least reactive? why?
C-F, strongest bond due to small atomic radius of F (despite F being the most electronegative)
what makes haloalkanes more reactive than alkanes?
polar C-X bond
why do nucleophilic substitution reactions of haloalkanes need alcoholic conditions (ethanol)?
improves solubility of halogenoalkane
in the reaction of a halogenoalkane with ammonia, what 2 conditions favour the formation of primary amines?
- high pressure
- ammonia in excess
why is the reaction of a halogenoalkane with ammonia done in a sealed tube?
to stop gaseous NH3 escaping
difference between NaOH(aq) and NaOH(alc) heated with a halogenoalkane?
aq - nucleophilic substitution
alc- elimination
what is an elimination reaction?
reaction in which a small molecule is removed from an organic compound
what does the OH- act as in an elimination reaction?
a base (proton acceptor, BL definition)
when is there the possibility of multiple products being formed by elimination?
when the halogenoalkane
is asymmetric about the carbon-halogen bond i.e. the molecule has different length carbon chains either
side of the C-X bond
difference between primary secondary and tertiary haloalkanes?
- primary haloalkanes tend towards substitution (even if NaOH is alcoholic)
- tertiary haloalkanes tend towards elimination
why is ozone necessary in the upper atmosphere?
absorbs UV radiation
what are chlorine radicals in the upper atmosphere formed from?
CFCs
how do CFCs form chlorine radicals in the upper atmosphere?
ultraviolet radiation causes C–Cl
bonds in chlorofluorocarbons (CFCs) to break.
why dont flourine radicals also form from CFCs in the upper atmosphere
the C-F bond is too strong to undergo homolytic fission due to uv light.
what is the formula of ozone?
O3
why are chlorine radicals dangerous in the upper atmosphere?
catalyse the breakdown of ozone and contribute to the hole in the ozone layer
what are the equations for cl radicals and ozone?
why can chlorine radicals able to break down many ozone molecules?
are regenerated in the reaction - chain reaction
