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Organic Chemistry > Alkenes > Flashcards

Alkenes Flashcards

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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

A

H-OSO3H

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
Q

Will asymmetrical alkenes form equal amounts of each product?

A

No. The more stable carbocation intermediary will form more products than the less stable one

26
Q

What is the mechanism to form a polymer ?

A

Addition polymerisation

27
Q

What is the repeating unit for poly (ethene)?

A 
H.  H
     |.   |
-(-C-C-)-
     |.   |
     H. H
28
Q

Give the IUPAC name for PVC?

A

poly(chloroethene)

29
Q

Describe normal PVC

A

Hard and rigid as there are permanent dipole-dipole forces between chains due to delta positive C and delta negative Cl

30
Q

Why are plasticisers added?

A

To reduce the effectiveness of the dipole dipole forces between PVC chains and make the plastic more flexible

31
Q

The more plasticiser you add…

A

The more flexible the plastic becomes

32
Q

What is the most common plasticiser?

A

Phthalates

33
Q

Give 3 uses of normal PVC

A

Doors
Windows
Guttering

34
Q

Give uses of plasticised PVC

A

Cable insulation
Imitation leather
Inflatable products

35
Q

What are the problems with plastics?

A

Non-biodegradable due to strong covalent bonds so buried plastics could take hundreds of years to decompose

36
Q

How are plastics broken down?

A

Heated or remoulded by heating so Van der Waals’ are broken

37
Q

What happens to poly(ethene)?

Poly(propene)?

A

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
Q

Typical uses of
Poly(ethene)
Poly(propene)

A

Plastic bags, washing up bowls

Rope

Organic Chemistry (12 decks)

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