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AS Chemistry > DF - Addition reactions of alkenes > Flashcards

DF - Addition reactions of alkenes Flashcards

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1
Q

Which are more reactive, single bonds or double bonds?

A

double

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2
Q

Why are double bonds more reactive than single bonds?

A

Because there’s more electron density in double bonds.

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3
Q

What do alkenes join up to form?

A

Addition polymers.

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4
Q

What is an addition polymer?

A

Alkenes joined together.

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5
Q

How do alkenes join together to form addition polymers?

A

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

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6
Q

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

A

Monomers.

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7
Q

What is polyethene made by?

A

Addition polymerisation of ethene.

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8
Q

What does adding hydrogen to C=C bonds produce?

A

Alkanes.

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9
Q

Ethene will react with hydrogen to produce…

A

Ethane

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10
Q

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

A

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

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11
Q

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

A

bromine water

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12
Q

How do you test for C=C bonds?

A

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

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13
Q

What is the use of bromine water a test for?

A

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

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14
Q

What is bromine reacting with an alkene an example of?

A

Electrophilic addition.

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15
Q

Give an example of electrophilic addition

A

bromine reacting with an alkene

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16
Q

What are electrophiles?

A

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

17
Q

What is electrophilic addition?

A

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.

18
Q

What do electrophilic addition reactions happen to?

A

Alkenes

19
Q

What can a double bond be described as being?

A

nucleophilic

20
Q

What does it mean that a double bond is nucleophilic?

A

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

21
Q

What do electrophilic addition reactions do to the double bond?

A

Open it up.

22
Q

What does a curly arrow mean?

A

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

23
Q

What is a carbocation?

A

An organic ion containing a positively charged carbon atom.

24
Q

What do alkenes undergo addition with?

A

Halides and hydrogen halides.

25
Q

What forms when alkenes undergo addition with hydrogen halides?

A

Halide alkanes.

26
Q

What does heterolytic mean?

A

Unequal.

27
Q

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

A

2

28
Q

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

A

Alcohols.

29
Q

How are alcohols produced?

A

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

30
Q

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

A

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.

31
Q

What is hydrolysis?

A

The breaking of covalent bonds by reaction with water.

32
Q

What is ethanol manufactured by?

A

Steam hydration.

33
Q

How can ethene be made into ethanol by steam hydration?

A

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

34
Q

What is the steam hydration of ethene into ethanol like?

A

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

AS Chemistry (44 decks)

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