DF - Addition reactions of alkenes Flashcards
Which are more reactive, single bonds or double bonds?
double
Why are double bonds more reactive than single bonds?
Because there’s more electron density in double bonds.
What do alkenes join up to form?
Addition polymers.
What is an addition polymer?
Alkenes joined together.
How do alkenes join together to form addition polymers?
The double bonds can open up and join together to make long chains called polymers.
What are alkenes examples of when they are in a polymer?
Monomers.
What is polyethene made by?
Addition polymerisation of ethene.
What does adding hydrogen to C=C bonds produce?
Alkanes.
Ethene will react with hydrogen to produce…
Ethane
What conditions need to be present for ethene to react with hydrogen to produce ethane?
A catalyst - either a nickel catalyst and a temperature of 150 degrees celsius and a high pressure or a platinum catalyst at room temperature.
What do you use to test for C=C bonds?
bromine water
How do you test for C=C bonds?
Shake an alkene with orange bromine water, the solution quickly decolourises if C=C bonds are present.
What is the use of bromine water a test for?
Unsaturation (the presence of double or triple carbon-carbon bonds).
What is bromine reacting with an alkene an example of?
Electrophilic addition.
Give an example of electrophilic addition
bromine reacting with an alkene
What are electrophiles?
Electron-pair acceptors (such as positively charged ions and polar molecules). They are attracted to areas where there are lots of electrons about.
What is electrophilic addition?
The double bonds open up and atoms are added to the carbon atoms because the double bond has got plenty of electrons and is easily attacked by electrophiles.
What do electrophilic addition reactions happen to?
Alkenes
What can a double bond be described as being?
nucleophilic
What does it mean that a double bond is nucleophilic?
It’s attracted to places that don’t have enough electrons.
What do electrophilic addition reactions do to the double bond?
Open it up.
What does a curly arrow mean?
Shows the movement of a pair of electrons. It starts from an electron pair - a covalent bond or a lone pair.
What is a carbocation?
An organic ion containing a positively charged carbon atom.
What do alkenes undergo addition with?
Halides and hydrogen halides.
What forms when alkenes undergo addition with hydrogen halides?
Halide alkanes.
What does heterolytic mean?
Unequal.
If hydrogen halides such as HBr adds to an unsymmetrical alkene like propene, how many possible products are there?
2
What does reacting alkenes with water and a sulfuric acid catalyst make?
Alcohols.
How are alcohols produced?
Industrially by hydrating alkenes in the presence of an acid catalyst such as sulfuric acid.
Describe how an alcohol is formed in the presence of sulfuric acid.
Cold concentrated sulfuric acid reacts with an alkene in an electrophilic addition reaction.
If you then add cold water and warm the product, it’s hydrolysed to form an alcohol.
What is hydrolysis?
The breaking of covalent bonds by reaction with water.
What is ethanol manufactured by?
Steam hydration.
How can ethene be made into ethanol by steam hydration?
Ethene can be hydrated by steam at 300 degrees celsius and a pressure of 60 atm. It needs a solid phosphoric(V) acid catalyst.
What is the steam hydration of ethene into ethanol like?
Reversible reaction with a low reaction yield (5%). You can recycle the unreacted ethene gas, making the overall yield a much more profitable 95%.