6.26 - Addition reactions of alkenes

Question 1

What is an addition reaction?

Answer 1

When two molecules combine to form one molecule

Question 2

What feature of alkenes allows them to undergo addition reactions?

Answer 2

Their double bond

Question 3

Why?

Answer 3

Because the double bond can become a single bond and allow two more groups to attach to the newly formed alkane

Question 4

What happens when bromine reacts with ethene?

Answer 4

1,2-dibromoethane is formed

Question 5

What is observed during this reaction?

Answer 5

There is a colour change from orange to colourless

Question 6

What is hydrogenation?

Answer 6

The addition of hydrogen to a molecule

Question 7

When an alkene is hydrogenised, what is formed?

Answer 7

An alkane with the same length carbon chain

Question 8

What are the conditions for the hydrogenation of ethene?

Answer 8

Heat and a nickel catalyst

Question 9

What is halogenation?

Answer 9

The addition of a halogen molecule to an alkene

Question 10

What will be formed?

Answer 10

A halogenoalkane

Question 11

What is a hydration reaction?

Answer 11

Adding water to a molecule

Question 12

What is formed?

Answer 12

An alcohol, as a hydrogen atom and OH group are added, and -OH is the funtional group of alcohols

Question 13

What catalyst is required?

Answer 13

Phosphoric acid

Question 14

What is a diol?

Answer 14

A compound containing two OH groups

Question 15

How are diols formed?

Answer 15

By adding water and an oxidising agent to an alkene

Question 16

Why does this work?

Answer 16

• Water splits into H and OH
• Oxygen from oxidising agent bonds to H
• Forming another OH group
• Both groups are added to the alkene