Halogenoalkanes Flashcards
as chem
When naming halogenalkanes what are the key concepts?
Same as usual rules
When determining prefix if there is more than 1 halogen name in alphabetical order.
Describe boiling point trend in halogenoalkanes
Boiling point increases down the group as strength of intermolecular forces increases.
This is due to the increased number of electrons In the halogens which then means stronger van Der daal forces between molecules so more energy is needed to overcome these forces.
What type of bond do halogenoalkanes have and what attacks them?
They have polar bonds as halogens are electronegative
Nucleophiles attack them
What is a nucelophile? give examples
A nucleophile is an electron pair donor.
CN-
NH3
OH-
What mechanisms do halogenoalkanes under go?
nucleophilic substitution reactions
Describe conditions + products of nucleophilic substitution reaction involving hydroxide ions..
CONDITIONS:
Warm aqueous sodium hydroxide (source of OH-)
2) carried out under reflux
PRODUCTS:
alcohol formed
Describe conditions + products of nucleophilic substitution reaction involving cyanide ions..
CONDITIONS:
warm ethanolic potassium cyanide
carried out under reflux
PRODUCT :
nitrile
Describe conditions + products of nucleophilic substitution reaction involving ammonia..
CONDITIONS:
heat with ethanol ammonia
excess ammonia
PRODUCTS:
amine
ammonium ion
Describe halogenoalkane reactivity..
HA become more reactive going down the group.
(this is because bond enthalpy between carbon and halogens decrease down group so less energy required for reaction to occur)
What determines reactivity?
Bond strength/enthalpy NOT bond polarity
Describe elimination reaction involving hydroxide ions and halogenoalkane..
CONDITIONS:
warm ethanolic sodium hydroxide
Carried out under reflux
How to differentiate hydroxide reaction from nucleophilic substitution and elimination?
Depends on solvent.
nucleophilic substitution : aqueous (water) solvent
elimination: if alcohol mentioned
PRODUCT:
alkene
water (h20)
What are CFC’S and what do they do?
CFCs are molecules that have had all their hydrogens replaced by chlorine and fluorine. They are stable until exposed to UV radiation.
Chloroflourocarbons break down ozone (o3) in the atmosphere as when they are exposed to uv radiation they are broken down into radicals which catalyse the break down of ozone.
What are restrictions of using CFC’S?
CFC’S are banned now as risks outweigh benefits as they damage ozone layer.
