Alkenes

Question 1

What is an alkene?

Answer 1

Unsaturated hydrocarbon

Question 2

Alkene general formula?

Answer 2

CnH2n

Question 3

What is a stereoisomer?

Answer 3

Same structural formula different spatial arrangement of atoms.

Question 4

What kind of isomerism do alkenes show?

Answer 4

E-Z isomerism

Question 5

When do E-Z isomers exist?

Answer 5

Restricted rotation around C=C double bond.
Two different groups/atoms attached to both ends of the double bond.

Question 6

What is the priority group?

Answer 6

The atom with the bigger atomic number.

Question 7

What is E isomer?

Answer 7

Epposite side

Question 8

What is Z isomer?

Answer 8

Z isomer.

Question 9

What is an electrophile?

Answer 9

An electron pair acceptor.

Question 10

What is an addition reaction?

Answer 10

A reaction where two molecules react together to produce one.

Question 11

Describe the double bonds in alkenes.

Answer 11

The double bonds in alkenes are areas with high electron density. This attracts electrophiles and the alkenes undergo addition reactions.

Question 12

What is the change in the functional group in the reaction of bromine with an alkene?

Answer 12

Alkene -> Dihalogenoalkane

Question 13

What is the reagents used in the reaction of bromine with an alkene?

Answer 13

Bromine

Question 14

What is the condition used in the reaction of bromine with an alkene?

Answer 14

Room temperature (not in UV light)

Question 15

What is the mechanism used in the reaction of bromine with an alkene?

Answer 15

Electrophillic addition

Question 16

What is the carbon atom with a + charge called?

Answer 16

Carbocation

Question 17

Explain why there is an attraction between a C=C double bond and Br2.

Answer 17

C=C has a high electron density.
Br-Br becomes polarised.
Br S+ is attracted to C=C.

Question 18

What is the change in the functional group in the reaction of Hydrogen bromide with an alkene?

Answer 18

Alkene -> Halogenoalkane

Question 19

What is the reagent used in the reaction of Hydrogen bromide with an alkene?

Answer 19

HBr or HCl

Question 20

What is the condition used in the reaction of Hydrogen bromide with an alkene?

Answer 20

Room temperature

Question 21

What is the mechanism used in the reaction of Hydrogen bromide with an alkene?

Answer 21

Electrophillic addition

Question 22

What causes two products to form?

Answer 22

Unsymmetrical alkene

Question 23

What is the S+ atom attracted to?

Answer 23

Electron rich pi bond.

Question 24

Order of stability for carbocations?

Answer 24

Tertiary>Secondary>Primary

Question 25

Why is the carbocation intermediate more stable in secondary than primary?

Answer 25

The methyl groups on either side of the positive carbon are electron releasing and reduce the charge on the ion which stabilises it.

Question 26

What forms the major product in electrophillic addition?

Answer 26

The more stable carbocation intermediate

Question 27

In an exam, what do you write when determining the major product?

Answer 27

1) Draw out both carbocations and identify as primary, secondary or tertiary. 2)State which is more stable. 3)State the reason why it is more stable.

Question 28

What if both are secondary?

Answer 28

Then both will be equally stable and a 50/50 split will be achieved.

Question 29

2 equations for sulfuric acid?

Answer 29

H2SO4 OSO2OH

Question 30

What are the two stages for the reaction of sulfuric acid with alkenes?

Answer 30

1)Electrophillic addition 2)Hydrolysis

Question 31

What is the change in the functional group for the reaction of sulfuric acid with alkenes (stage 1)?

Answer 31

Alkene -> Alkyl hydrogensulfate

Question 32

What is the reagent used for the reaction of sulfuric acid with alkenes (stage 1)?

Answer 32

Concentrated H2SO4

Question 33

What is the condition used for the reaction of sulfuric acid with alkenes (stage 1)?

Answer 33

Room temperature

Question 34

What is the mechanism used for the reaction of sulfuric acid with alkenes (stage 1)?

Answer 34

Electrophillic addition

Question 35

What is the reagent used for the reaction of sulfuric acid with alkenes (stage 2)?

Answer 35

Water

Question 36

What is the change in the functional group for the reaction of sulfuric acid with alkenes (stage 2)?

Answer 36

Alkyl hydrogensulfate -> Alcohol

Question 37

What is the condition used for the reaction of sulfuric acid with alkenes (stage 2)?

Answer 37

Warm mixture

Question 38

What is the mechanism used for the reaction of sulfuric acid with alkenes (stage 2)?

Answer 38

Hydrolysis

Question 39

What is the role of H2SO4 and why?

Answer 39

Catalyst because it is regenerated.

Question 40

What is hydrolysis?

Answer 40

A reaction where the molecule is split by the addition of water.