The formation of halogeonalkanes Flashcards
In what condition does a halogen and alkane need to be under in order for them to react?
In bright sunlight (ultraviolet light), above room temperature
What is the type of reaction that takes place when a halogen and alkane react?
A substitution reaction
What type of substitution reaction is it?
A free-radical substitution
What are the three stages in this chain reaction?
Initiation
Propagation
Terminiation
What happens in the initiation stage of the reaction?
The halogens come in pairs, and the fist step is to brake that bond between the atoms.
Why does the bonds between the halogens break?
Because the halogens absorb ta single quantum of UV light, which has more energy than the bonds between the two halogens, so the bond breaks
Since both of the atoms are the same, in which way will they break?
Homolytically (Greek word for equally)
What does homolytically mean?
One of the shared electrons move to the separate atoms.
Now the halogen atoms have an unpaired electron. So what can you call them?
Free radicals!
On a diagram how could you show that an atom has an unpaired electron?
With a dot next to the atom
Why does the carbon-hydrogen bond not break under the ultraviolet light?
Because they require more energy to break
Why does the carbon-hydrogen bond not break under the ultraviolet light?
Because they require more energy to break
What is the first stage of propagation?
The halogen free radical takes a hydrogen atom from the hydrocarbon to form hydrogen chloride. This leaves a free radical on the hydrocarbon chain.
What is the second stage of propagation?
The hydrocarbon chain is now very reactive and so reacts with the last halogen molecule. This produces another halogen free radical and a molecule of a halogenoalkane.
What is the second stage of propagation?
The hydrocarbon chain is now very reactive and so reacts with the last halogen molecule. This produces another halogen free radical and a molecule of a halogenoalkane.
