DF - Addition reactions of alkenes

Question 1

Which are more reactive, single bonds or double bonds?

Answer 1

double

Question 2

Why are double bonds more reactive than single bonds?

Answer 2

Because there’s more electron density in double bonds.

Question 3

What do alkenes join up to form?

Answer 3

Addition polymers.

Question 4

What is an addition polymer?

Answer 4

Alkenes joined together.

Question 5

How do alkenes join together to form addition polymers?

Answer 5

The double bonds can open up and join together to make long chains called polymers.

Question 6

What are alkenes examples of when they are in a polymer?

Answer 6

Monomers.

Question 7

What is polyethene made by?

Answer 7

Addition polymerisation of ethene.

Question 8

What does adding hydrogen to C=C bonds produce?

Answer 8

Alkanes.

Question 9

Ethene will react with hydrogen to produce…

Answer 9

Ethane

Question 10

What conditions need to be present for ethene to react with hydrogen to produce ethane?

Answer 10

A catalyst - either a nickel catalyst and a temperature of 150 degrees celsius and a high pressure or a platinum catalyst at room temperature.

Question 11

What do you use to test for C=C bonds?

Answer 11

bromine water

Question 12

How do you test for C=C bonds?

Answer 12

Shake an alkene with orange bromine water, the solution quickly decolourises if C=C bonds are present.

Question 13

What is the use of bromine water a test for?

Answer 13

Unsaturation (the presence of double or triple carbon-carbon bonds).

Question 14

What is bromine reacting with an alkene an example of?

Answer 14

Electrophilic addition.

Question 15

Give an example of electrophilic addition

Answer 15

bromine reacting with an alkene

Question 16

What are electrophiles?

Answer 16

Electron-pair acceptors (such as positively charged ions and polar molecules). They are attracted to areas where there are lots of electrons about.

Question 17

What is electrophilic addition?

Answer 17

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.

Question 18

What do electrophilic addition reactions happen to?

Answer 18

Alkenes

Question 19

What can a double bond be described as being?

Answer 19

nucleophilic

Question 20

What does it mean that a double bond is nucleophilic?

Answer 20

It’s attracted to places that don’t have enough electrons.

Question 21

What do electrophilic addition reactions do to the double bond?

Answer 21

Open it up.

Question 22

What does a curly arrow mean?

Answer 22

Shows the movement of a pair of electrons. It starts from an electron pair - a covalent bond or a lone pair.

Question 23

What is a carbocation?

Answer 23

An organic ion containing a positively charged carbon atom.

Question 24

What do alkenes undergo addition with?

Answer 24

Halides and hydrogen halides.

Question 25

What forms when alkenes undergo addition with hydrogen halides?

Answer 25

Halide alkanes.

Question 26

What does heterolytic mean?

Answer 26

Unequal.

Question 27

If hydrogen halides such as HBr adds to an unsymmetrical alkene like propene, how many possible products are there?

Answer 27

2

Question 28

What does reacting alkenes with water and a sulfuric acid catalyst make?

Answer 28

Alcohols.

Question 29

How are alcohols produced?

Answer 29

Industrially by hydrating alkenes in the presence of an acid catalyst such as sulfuric acid.

Question 30

Describe how an alcohol is formed in the presence of sulfuric acid.

Answer 30

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.

Question 31

What is hydrolysis?

Answer 31

The breaking of covalent bonds by reaction with water.

Question 32

What is ethanol manufactured by?

Answer 32

Steam hydration.

Question 33

How can ethene be made into ethanol by steam hydration?

Answer 33

Ethene can be hydrated by steam at 300 degrees celsius and a pressure of 60 atm. It needs a solid phosphoric(V) acid catalyst.

Question 34

What is the steam hydration of ethene into ethanol like?

Answer 34

Reversible reaction with a low reaction yield (5%). You can recycle the unreacted ethene gas, making the overall yield a much more profitable 95%.