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AS Chemistry - Unit 2 > Unit 3,2,9 - Alkenes > Flashcards

Unit 3,2,9 - Alkenes Flashcards

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1
Q

What are alkenes?

A

Unsaturated hydrocarbons containing C=C bonds.

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2
Q

What is the arrangement and the bond angle between a C=C bond?

A

Planar arrangement - 120.

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3
Q

What are stereoisomers?

A

Molecules with the same molecular formula and the same arrangement of covalent bonds but different arrangement in space.

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4
Q

Why can alkenes present stereoisomerisms?

A

They can’t rotate about the double bond.

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5
Q

What are the two types of isomers within stereoisomerism?

A

E and Z

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6
Q

What are E isomers?

A

When the groups are attached on opposite sides of the double bond.

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7
Q

What are Z isomers?

A

When the groups are attached together on the same side of the double bond.

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8
Q

Draw an E and Z isomer of dichloroethene

A

See Flash Card

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9
Q

Why can a double bond attract electrophiles?

A

The double bond is a centre of high electron density so has a slightly negative charge.

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10
Q

What is an electrophile?

A

Electron pair acceptors.

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11
Q

Give three examples of electrophiles?

A

Halogens, Hydrogen Halides, Sulphuric Acid.

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12
Q

What type of reaction do alkenes go under with electrophiles?

A

Electrophilic Addition

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13
Q

Draw the mechanism for the electrophilic addition between Ethene and a Halogen.

A

See Flash Card

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14
Q

Draw the mechanism for the electrophilic addition between Ethene and Hydrogen Halide.

A

See Flash Card

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15
Q

Draw the mechanism for the electrophilic addition between Ethene and Sulphuric Acid.

A

See Flash Card

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16
Q

How can we test for the presence of Alkenes and what are the results you would expect?

A

Mix the solution with orange bromine water.

In the presence of an Alkene it will turn from orange to colourless.

17
Q

Why does Bromine water turn colourless in Alkenes?

A

Bromine is added to the double bond by electrophilic addition forming a colourless dibromoalkane.

18
Q

During electrophilic addition, which product is most likely to form?

A

One where the carbon holding the carbocation is attached to the most other carbon atoms.

19
Q

What two methods are there for producing alcohols?

A
  1. ) Steam hydration of ethane

2. ) Hydrating alkenes in the presence of an acid catalyst

20
Q

Name three conditions for when ethane is hydrated by steam to produce ethanol.

A

300C
60atm
Solid Phosphoric Acid Catalyst

21
Q

What is the first step when alkenes are hydrated to alcohols?

A

They are reacted with concentrated Sulphuric Acid

22
Q

How are alkenes hydrated to alcohols?

A

They are reacted with water in the presence of cold concentrated sulphuric acid.

23
Q

What is the overall equation for when ethane is hydrated to ethanol?

A

……..

24
Q

What is addition polymerisation?

A

Alkenes are joined up together under high pressure with a suitable catalyst.

25
Q

What does addition polymerisation produce?

A

A polyalkene

26
Q

What is a Polyalkene

A

Very long hydrocarbon chain

27
Q

Draw an addition polymerisation reaction between n lots of Ethene.

A

See flash card

28
Q

How do you find the monomer used to form a polyalkene?

A

You take the repeating unit and a double bond in the middle.

29
Q

Give two properties and two uses of low density polyethene.

A
  1. ) Soft and flexible

2. ) Plastic bags and bottles

30
Q

Give two properties and two uses of polypropene

A
  1. ) Tough and strong

2. ) Crates and straws

31
Q

How can Polypropene be recycled to make new products?

A

It can be melted and remoulded.

32
Q

Give two reasons why it’s best to recycle polymers.

A
  1. ) They are difficult to dispose of

2. ) They come from non renewable resources

33
Q

Give two reasons why polymers are difficult to dispose of.

A
  1. ) Non biodegradeable

2. ) Produce toxic fumes when burnt

AS Chemistry - Unit 2 (11 decks)

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