Reactions of alkanes Flashcards
what are free radicals?
particles that have unpaired electrons
What do alkanes react with?
Alkanes react with particles that have unpaired electrons (called free radicals). These reactions happen in several steps.
What is bond fission?
The breaking of covalent bonds.
What are the two ways in which bond fission can take place?
A single covalent bond is a shared pair of electron between two atoms. It can break in to ways:
What do curly arrows show you?
Th movement of an electron pair.
What type of reaction allows halogens to react with alkanes?
- halogens react with alkanes in photochemical reactions (reactions started by light) - in this case ultraviolet light
- a hydrogen atom is substituted (replaced) by chlorine or bromine.
- this is a free radical substitution reaction
What is heterolytic fission?
What is homolytic fission?;
What are the three stages of the reaction mechanism for free-radical substitution?
Initiation
Propogation
Termination
What do you need to remember about the first stage of the free radical substitution mechanism?
What do you need to remember about the second stage of the free radical substitution mechanism?
What doyou need to remeber about the final stage of the free radical subsitution mechanism?
What are the problems with free radical substitution?
- When you’re trying to make a particular product, you get a mixture of products.
- Another probelm with free radical substitution is that it can take place at any point along the carbon chain. So a mixture of isomers can be formed.
For example, reacting propane with chlorine will produce a mixture of 1-chloropropane and 2-chloropropane.
Explain how a mixture of products are formed in the making of chloromethane.
What are the products of the free radical substitution of chloromethane.
Why is this a problem?
What is the best way of reducing the chance of by-products forming when making chloromethane through free radical substitution?
