Alkenes Flashcards

(38 cards)

1
Q

What is a C=C double bond?

A

An area of high electron density

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2
Q

Why are alkenes highly reactive?

A

Their C=C double bond

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3
Q

How is the C=C double bond formed?

A

The overlap of a spare unbonded singly filled p-orbital present on each carbon atom in the bond

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4
Q

Can a C=C double bond be rotated?

A

NOPE

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5
Q

What is the general formula for alkenes?

A

Cn H2n

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6
Q

What is the bond angle and shape name for the C=C double bond in alkenes?

A

120

Planar

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7
Q

When naming alkenes what must you always check for?

A

E/Z isomerism

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8
Q

What is the only mechanism in the alkenes topic?

A

Electrophilic addition

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9
Q

Are alkenes or alkanes more reactive?

A

Alkenes

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10
Q

What is an electrophile?

A

A species that Accepts a pair of electrons

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11
Q

What area of alkenes is easily attacked by electrophiles?

Why?

A

The C=C double bond

It has a high electron density

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12
Q

Describe the mechanism to turn alkenes to alkanes briefly

Give this mechanism’s name

A

An electron pair is donated to the electrophile which causes C=C double bond to break, allowing each C to form bonds with other species

Electrophilic addition

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13
Q

Describe the electrophilic addition mechanism with the electrophile X-Y

A

1) an e- pair from the C=C bond forms a covalent bond with the delta positive X, breaking the X-Y bond and forming a :Y- ion. An intermediate with a *ve carbocation is formed
2) lone pair on :Y- forms a covalent bond with +ve carbon

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14
Q

In electrophilic addition with Bromine water, what does the :Br- ion act as?

A

A nucleophile

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15
Q

Bromine water is non-polar. How does electrophilic addition occur?

A

Electron rich double bond induces a dipole and delta positive Br acts as the electrophile

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16
Q

In a H-X molecule, where X is a halogen atom, which is delta positive?

A

The H is delta positive

17
Q

How to write sulphuric acid for electrophilic addition

18
Q

What is hydrolysis?

A

Splitting a molecule with water or another small molecule

19
Q

What does the addition of ethyl hydrogen sulphate to water cause and produce?

What is the overall equation?

What does H2SO4 act as? Why?

A

Hydrolysis

Ethanol

CH2=CH2 +H2O —-> CH3CH2OH

A catalyst. It is not used up?

20
Q

What is the most stable carbocation?

The least stable?

A

Tertiary

Primary

21
Q

What is the major product formed from?

A

The more stable carbocation

22
Q

How do you determine the class of the carbocation?

A

The number of carbon atoms directly bonded to the positively charged carbon atom

23
Q

What is the stability of carbocations related to?

Why?

A

The presence of alkyl groups (CH3, CH2, CH)

Electron releasing relative to the hydrogen atoms and help to stabilise the positive charge on the carbocation

24
Q

What is the electron releasing property of alkyl groups called?

A

Positive inductive effect

25
Will asymmetrical alkenes form equal amounts of each product?
No. The more stable carbocation intermediary will form more products than the less stable one
26
What is the mechanism to form a polymer ?
Addition polymerisation
27
What is the repeating unit for poly (ethene)?
``` H. H |. | -(-C-C-)- |. | H. H ```
28
Give the IUPAC name for PVC?
poly(chloroethene)
29
Describe normal PVC
Hard and rigid as there are permanent dipole-dipole forces between chains due to delta positive C and delta negative Cl
30
Why are plasticisers added?
To reduce the effectiveness of the dipole dipole forces between PVC chains and make the plastic more flexible
31
The more plasticiser you add...
The more flexible the plastic becomes
32
What is the most common plasticiser?
Phthalates
33
Give 3 uses of normal PVC
Doors Windows Guttering
34
Give uses of plasticised PVC
Cable insulation Imitation leather Inflatable products
35
What are the problems with plastics?
Non-biodegradable due to strong covalent bonds so buried plastics could take hundreds of years to decompose
36
How are plastics broken down?
Heated or remoulded by heating so Van der Waals’ are broken
37
What happens to poly(ethene)? Poly(propene)?
It is separated from others, washed, melted, and remoulded Heated to high temp to break polymer bonds and produce monomers which can be used to make new plastics
38
Typical uses of Poly(ethene) Poly(propene)
Plastic bags, washing up bowls Rope