Halogenoalkanes Flashcards
How do halogenoalkanes form?
Through the placing a mixture of an alkane an a haloen into bright sunlight, the UV components of the ligh starts the reaction.
Why cannot halogenoalkans form in a dark room at room temperature?
This is because the reaction relys on the UV present in the light.
What type of reaction is the formation of halogenoalkanes?
A free-radical substitution.
What are the stages of a the free radical substitution reaction of the formation of halogenoalkanes?
Initiation, propagation and termination.
What is the initiation stage of a free-radical substitution reaction?
The breaking of the diatomic molecule to form two atoms which are free radicals. This happens due to the bond absorbing the energy of a single quantam of UV. These free radicals are highly reactive.
Why does the alkane not break down during the initiation step?
The energy of available in the UV light is not enough to break the C-H bond.
What are halogenoalkanes?
Alkanes with one or more halogens attached to it.
Explain the trend in boiling points of halogenoalkanes.
The boiling points increase down the group, this is due to the strength of intermolecular forces. Van der waals forces get stronger witg more electrons.
Why are halogenoalkanes attacked by nucleophiles?
They have a polar bond.
In which direction are the electrons pulled towards in a halogenoalkane and why?
Towards the halogens as the halogens are more electronegative than the carbons.
What is a nucleophile?
A substance that is an electron pair donor.
What are three examples of nucleophiles?
Ammonia
Hydroxide Ions
Cyanide Ions
How do halogenoalkanes react with hydroxide ions?
Via nucelophilc substitution.
What are the conditions for the nucleophilic substiution involving halogenoalkanes and hydroxide ions?
Warm aqueous sodium hydroxide and it is carried under reflux.
What do halogenoalkanes react with cyanide ions to make?
Nitriles.
What are the conditions for the reaction between cyanide ions and halogenoalkanes?
Warm ethanolic potassium cyanide and it is carried out under reflux.
What does the nucleophilic substitution of halogenoalkanes with hydroxide ions create?
Alcohols.
How do halogenoalkanes react with ammonia?
Via nucleophilic substitution.
What are the conditions of the nucleophilic substitution of halogenoalkanes with ammonia?
Heat with ethanolic ammonia and an excess of ammonia.
What is produced from the nucleophilic substitution of halogenoalkanes and ammonia?
An amine.
Describe the trend in reactivity of halogenoalkanes down the group.
Reactivity increases dow the group.
How do halogenoalkanes react with hydroxide ions via elimination?
Using ethanol solvent.
What solvent does the elimination reaction of halogenoalkanes with hydroxide ions require?
Ethanol solvent.
What are the conditions of the elimination reaction of halogenoalkanes and hydroxide ions?
Warm ethanolic sodium hydroxide and it is carried out under reflux.
What does the elimination reaction between halogenoalkanes and hydroxide ions produce?
An alkene.
What do chlorofluorocarbons break down in the atmosphere?
Ozone.
Why are C-Cl bonds broken the easiest by UV?
They have the lowest bond enthalpy.
What is an alternative to CFC’s?
Hydrofluorocarbons.
