14.2- REACTION OF ALKENES

Question 1

Are alkenes used as fuels?

Answer 1

no

Question 2

Why are alkenes not used as fuels?

Answer 2

their reactivity makes them very useful for other purposes

Question 3

What is the reaction of alkenes typically?

Answer 3

electrophilic additions

Question 4

What makes the carbon-carbon double bond a centre of high electron density?

Answer 4

the four electrons in the carbon-carbon double bond

Question 5

What are electrophiles attracted towards on an alkene?

Answer 5

carbon-carbon double bond which is the centre of electron density

Question 6

What can electrophiles use to bond with alkenes?

Answer 6

by using two of the four electrons in the carbon-carbon double bond

Question 7

Where do hydrogen halides add on an alkene?

Answer 7

across the double bond

Question 8

When hydrogen halides add across the double bond of an alkene, what is formed?

Answer 8

halogenoalkane

Question 9

What can happen when the double bond is not exactly in the middle when a hydrogen halide is added?

Answer 9

there are two possible products

Question 10

What do the alkyl groups have a tendency to do?

Answer 10

release electrons

Question 11

What is the tendency of the alkyl groups to release electrons called?

Answer 11

positive inductive effect

Question 12

How is the positive inductive effect sometimes represented?

Answer 12

by an arrow along their bonds to show the direction of the release

Question 13

What does the electron-releasing affect of the alkyl groups tend to do to the intermediate carbocation?

Answer 13

stabilise the positive charge of the intermediate carbocation

Question 14

What is the affect on the carbocation the more the alkyl groups attached to the positively charged carbon atom?

Answer 14

the more stable the carbocation is

Question 15

Order the stability of a secondary carbocation, tertiary carbocation and primary carbocation?

Answer 15

tertiary
secondary
primary

Question 16

What will the product from an asymmetrical alkene tend to come from?

Answer 16

the more stable carbocation

Question 17

How fast do alkenes react with chlorine, bromine or iodine?

Answer 17

rapidly

Question 18

What is produced when alkenes react with chlorine, bromine or iodine?

Answer 18

dihalogenoalkanes

Question 19

How does a halogen add to the alkene?

Answer 19

across the double bond

Question 20

What does the halogen act as when a halogen and alkene react?

Answer 20

electrophile

Question 21

What are the two steps for when an alkene and halogen add?

Answer 21

formation of carbocation by electrophilic addition

rapid reaction with negative ion

Question 22

What is the bromine water test?

Answer 22

when a few drops of bromine water (reddish-brown) is added to an alkene, solution decolourised

Question 23

When bromine water is added to an alkene, why is the solution decolourised?

Answer 23

the products are colourless

Question 24

At what temperature does the reaction occur when concentrated sulphuric acid adds across the double bond of an alkene?

Answer 24

at room temperature

Question 25

Is it an exothermic or endothermic reaction when concentrated sulphuric acid adds across a double bond of an alkene?

Answer 25

exothermic

Question 26

What is the electrophile in a sulphuric acid molecule?

Answer 26

partially positive charged hydrogen atom

Question 27

What is formed when water is added to the product of the addition of concentrated sulphuric acid to an alkene?

Answer 27

an alcohol

Question 28

What is reformed when water is added to the product of the addition of concentrated sulphuric acid to an alkene?

Answer 28

sulphuric acid

Question 29

As sulphuric acid is reformed when water is added to the product of concentrated sulphuric acid and an alkene, what does the sulphuric acid act as?

Answer 29

catalyst

Question 30

How can you predict the products with an asymmetrical alkene?

Answer 30

by looking at the relative stability of the possible carbocations that could form

Question 31

Can water add across the double bond of alkenes?

Answer 31

yes

Question 32

How is the water being able to add across the double bond on alkenes used industrially?

Answer 32

to make alcohols

Question 33

At what conditions is water added across the double bond in alkenes to make alcohols? (4)

Answer 33

carries out with steam suitable temperature suitable pressure acid catalyst i.e. phosphoric acid

Question 34

Equation for when water is added across the double bond of ethene?

Answer 34

CH2=CH2 (g) + H20 (g) = CH3CH2OH (g)