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AS Chemistry > Alkenes > Flashcards

Alkenes Flashcards

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1
Q

What is an alkene?

A

An unsaturated hydrocarbon with a carbon carbon double bond

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2
Q

How can you make alkenes?

A

Cracking

Elimination of halogenoalkanes

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3
Q

What is the general formula for alkenes?

A

CnH2n

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4
Q

What is the test for unsaturation?

A

Bromine water makes alkenes go from orange to colourless

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5
Q

What causes E-Z isomerism?

A

Restricted rotation around the double bond

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6
Q

What is stereoisomerism?

A

When molecules have the same structural formula but the atoms/groups have a different arrangement in 3D space

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7
Q

What is EZ isomerism?

A

When molecules have the same structural formula but a different arrangement of atoms in 3D space around a double bond

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8
Q

What are isomers?

A

Molecules with the same molecular formula but a different structural formula

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9
Q

What is addition polymerisation?

A

When alkenes react together to form addition polymers

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10
Q

What is a monomer?

A

The unit which breaks its double bond and forms polymers

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11
Q

What is a polymer?

A

A long chain of repeating monomer units joined together

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12
Q

What are the two types of poly(ethene)

A

Low density poly(ethene) and high density poly(ethene)

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13
Q

What are the conditions under which LDPE is made?

A

200 degrees celcius, 120000kPa with little oxygen

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14
Q

Describe the structure of LDPE

A

Branched chains which don’t pack closely together and softens at temps below 100

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15
Q

What are the conditions under which HDPE is made?

A

60 degrees celcius, titanium chloride catalyst

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16
Q

Describe the structure of HDPE

A

Straight chains which can pack more tightly together. Softens at higher temperatures

17
Q

What is PVC?

A

poly(chloroethane)

18
Q

How is PVC made softer?

A

Plasticiser which makes it more flexible

19
Q

What bonds hold monomers together?

A

Covalent bonds

20
Q

What bonds hold polymer molecules together?

A

Van der Waals forces

21
Q

What are the problems with polymers?

A

Not biodegradable, take years to decompose, platic liter can be ingested by animals, non-renewable oil and if incinerated it produces toxic CO2 gas

22
Q

What are electrophiles?

A

Electron pair acceptors

23
Q

Why do electrophiles attack double bonds?

A

Bc they’re areas of high electron density

24
Q

In electrophilic addition with bromine, what are the conditions?

A

Alkenes
Bromine
Room temp
No light

25
Q

In the electrophilic addition with hydrogen bromide, what are the conditions?

A

Heat under reflux, alkenes, phosphoric (V) acid catalyst and sodium halide

26
Q

When can more than one product be formed from electrophilic addition?

A

When the alkene is unsymmetrical

27
Q

What is the most stable product in any electrophilic addition and why?

A

The one with more alkyl groups attached, bc alkyl groups have a positive inductive effect which pushes electrons towards the carbocation and stabilises its charge

28
Q

What is Markovnikov’s rule?

A

The hydrogen halide adds on so that the hydrogen atom adds to the carbon which already has the most hydrogens

29
Q

What is a carbocation?

A

A species which contains a positive charge on the carbon atom

30
Q

What is an addition reaction?

A

A reaction in which two molecules join together to make one larger molecule

31
Q

What is heterolytic fission?

A

When a covalent bond break and both electrons in the bond move to one of the atoms

32
Q

What are the conditions needed for the electrophilic addition with sulfuric acid?

A

concentrated sulfuric acid, alkene and room temp

33
Q

What are the conditions needed in hydration?

A

Stean, pressures of 60atm and 600K and a concentrated strong acid catalyst

34
Q

What is the functional group of alkenes?

A

C=C

35
Q

What is uPVC used for?

A

Window and door frames and drainpipes

36
Q

What is PVC used for?

A

Clothing and wellington boots

AS Chemistry (14 decks)

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