3.3 Haloalkanes Flashcards
General formula of haloalkanes
CnH2n+1X
Uses of haloalkanes
PVC (window frames, drainpipes)
Solvents
Anaesthetics
More reactive than alkanes
Explain the most important factor when it comes to reactivity of haloalkanes
Bond energies/enthalpy
-the shorter the bond
-the stronger
-therefore takes more E to break
-therefore less reactive
-the longer the bond
-the weaker
-therefore most reactive and fastest rate of reaction
Explain how bond polarities affect reactivity
with increasing electronegativity the greater diff in electronegativity between C and X
therefore the more polar the bond
Define hydrolysis
Splitting of a bond using elements of water
Explain how nucleophilic substitution of a haloalkane to an alcohol works
(hydrolysis)
NaOH (aq) or KOH (aq) + alcohol
OH nucleophile attacks carbon in carbon-halogen bond
OH replaces halogen
2 arrows
Halide ion is leaving group
Explain how nucleophilic substitution of a haloalkane to a nitrile works
Nucleophile attacks first carbon and a pair of electrons transferred to the halogen
CN nucleophile
EXTENDS THE LENGTH OF THE CARBON CHAIN
Explain how nucleophilic substitution of a haloalkane to an amine works
Conditions: HIGH PRESSURE as ammonia is gaseous
NH3 nucleophile
2 ammonias used
Positive charge on N in the intermediate as it donates 2 instead of 1 electron
Explain how elimination of a haloalkane to an alkene works
OH nucleophile acts as a base
Produces an alkene, halide ion and molecule of water
Sometimes there are E/Z ISOMERS of the alkene produced
Uses of CFCs
short molecules (g)- refrigerants and propellants
long molecules (l)- dry cleaning liquids
Effect of CFCs on the environment
UV
breaks the C-Cl bonds as they are weaker (because they are longer) releasing chlorine free radicals
which react with ozone in FRS producing oxygen
-therefore ozone is destroyed (no protection from UV as ozone absorbs UV-causes skin cancer)
