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Flashcards in Alkenes Deck (38)
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1

What is a C=C double bond?

An area of high electron density

2

Why are alkenes highly reactive?

Their C=C double bond

3

How is the C=C double bond formed?

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

4

Can a C=C double bond be rotated?

NOPE

5

What is the general formula for alkenes?

Cn H2n

6

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

120

Planar

7

When naming alkenes what must you always check for?

E/Z isomerism

8

What is the only mechanism in the alkenes topic?

Electrophilic addition

9

Are alkenes or alkanes more reactive?

Alkenes

10

What is an electrophile?

A species that Accepts a pair of electrons

11

What area of alkenes is easily attacked by electrophiles?

Why?

The C=C double bond

It has a high electron density

12

Describe the mechanism to turn alkenes to alkanes briefly

Give this mechanism’s name

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

13

Describe the electrophilic addition mechanism with the electrophile X-Y

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

14

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

A nucleophile

15

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

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

16

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

The H is delta positive

17

How to write sulphuric acid for electrophilic addition

H-OSO3H

18

What is hydrolysis?

Splitting a molecule with water or another small molecule

19

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

What is the overall equation?

What does H2SO4 act as? Why?

Hydrolysis

Ethanol

CH2=CH2 +H2O —-> CH3CH2OH

A catalyst. It is not used up?

20

What is the most stable carbocation?

The least stable?

Tertiary

Primary

21

What is the major product formed from?

The more stable carbocation

22

How do you determine the class of the carbocation?

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

23

What is the stability of carbocations related to?

Why?

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

What is the electron releasing property of alkyl groups called?

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