Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry OCR A A level > Alkenes > Flashcards

Alkenes Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What do alkenes contain?

A

One or more carbon-to-carbon double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the general formula of aliphatic hydrocarbons?

A

C(n)H(2n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is a pi bond formed from?

A

The sideways overlap of two p-orbitals one from each carbon atom of the double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where is pi bond electron density concentrated?

A

Above and below the plane of nuclei of bonded atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do pi bonds prevent? How?

A

Rotation around the double bond, due to the lock of the two carbon atoms leading to concentrated electron density above and below the plane of atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the shape around the carbon atoms in double bond of an alkene?

A

Trigonal Planar- three areas of electron density around each of the carbon atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define stereoisomers

A

Same structural formula but a different arrangement of the atoms in space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does stereoisomerism occur?

A

Due to the restricted rotation around the double bond, and therefore the groups attached to each carbon are fixed relative to each other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What two conditions have to be fulfilled for E/Z isomerism?

A

A C=C double bond

Different groups attached to each carbon atom of the double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What condition has to be different for cis-trans isomerism than E/Z isomerism?

A

In cis-trans isomerism one of the attached groups on the each carbon atom on the double bond must be the same.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a cis-isomer have?

A

The hydrogen atoms and methyl groups on each carbon in the double bond are on the same side.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What doe a trans-isomer have?

A

The hydrogen atoms and methyl groups on each carbon in the double bond are opposite each other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What occurs in a Z isomer?

A

The groups with higher priority are on the same side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What occurs in a E isomer?

A

The groups with higher priority are diagonally placed across the double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is priority assigned?

A

Based on atomic number. The higher the atomic number, the higher the priority.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens if the atom attached to carbon atom is the same when assigning priority?

A

Keep going along the molecule until reaches a difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why are alkenes more reactive than alkanes?

A

Pi bonds are the overlap of p orbitals above and below the plane of the sigma bond. Being above and below means more exposed electrons. Reacts more easily.

18
Q

What conditions are needed in the hydrogenation of an alkene?

A

423K

Nickel Catalyst

19
Q

What is hydrogenation?

A

The addition of H2 across a double bond

20
Q

How is unsaturation tested for?

A

Addition of bromine water. Colour change from orange to colourless if a double bond is present.

21
Q

What conditions are required for hydration of alkenes?

A

Steam

Concentration phosphoric acid catalyst

22
Q

Define ‘electrophilic addition’

A

An addition reaction in which the first step is attack by an electrophile on a region of high electron density

23
Q

Where is high electron density found?

A

Double bond of the alkene

24
Q

Define ‘electrophile’

A

An atom or group of atoms that is attracted to an electron rich centre and accepts an electron pair

25
Q

What is a carbocation?

A

Containing a positively charged carbon atom

26
Q

What is the most stable carbocation?

A

Tertiary carbocation

27
Q

What makes a carbocation more stable?

A

Each alkyl group pushes electrons towards the positive charge of carbocation
Positive charge is spread over alkyl groups
More alkyl group= more spread of charge= more stable

28
Q

What does Markownikoff’s rule state?

A

When a compound HX is added to an unsymmetrical alkene, the hydrogen becomes attached to the carbon with the most hydrogens attached to it already.

29
Q

What are polymers?

A

Long chains of repeating units of monomers

30
Q

What type of polymerisation do alkenes undergo?

A

Addition polymerisation to produce long saturated chains containing no double bonds.

31
Q

How does recycling alkene based polymers help?

A

Reduces environmental impact
Conserves finite fossil fuels
Reduces waste in landfill

32
Q

How are polymers recycled?

A 
Discarded polymers are sorted by type
Polymers chopped into flakes
Washed
Dried 
Melted
Recycled polymers cut into pellets
33
Q

Why is disposal of PVC hazardous?

A

High chlorine content

34
Q

What does PVC produce when burnt?

A

Corrosive hydrogen chloride gas

35
Q

How is PVC disposed of?

A

Solvents dissolve polymer

High grade polymers are recovered by precipitation from the solvent

36
Q

What is feedstock recycling?

A

Chemical and thermal process of reclaiming monomers from waste polymers

37
Q

What is the biggest advantage of feedstock recycling?

A

Can handle unsorted and unwashed polymers

38
Q

What are bioplastics?

A

Plastics produced from plant starch, cellulose, plant oils and proteins which are renewable and sustainable.

39
Q

How are biodegradable polymers broken down?

A

By microorganisms into carbon dioxide, water and biological molecules

40
Q

What are photodegradable polymers?

A

Polymers containing bonds that are weakened by absorbing light to start degradation

Chemistry OCR A A level (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions