Free Radical Substitution

Question 1

What is homolytic bond fission?

Answer 1

When the bond breaks. Each atom takes an electron from the bond. Cl atoms formed have an unpaired electron i.e. Free radical

Question 2

What is the equation for initiation?

Answer 2

Cl2 –> Cl• + Cl•

UV light

Question 3

What is the equation for propagation?

Answer 3

C2H6 + Cl• –> •C2H5 + HCl

Then:

•C2H5 + Cl2 –> C2H5Cl + Cl•

Question 4

What is the equation for termination?

Answer 4

Cl• + Cl• –> Cl2

• C2H5 + Cl• –> C2H5Cl
• C2H5 + •C2H5 –> C4H10

Question 5

What are the 3 step mechanisms in free radical substitution?

Answer 5

Initiation
Propagation
Termination

Question 6

What is nucleophillic substitution?

Answer 6

Nucleophile - something that attracted to the nucleus e.g. Electron

Substitution- replacing something for another

Question 7

CH4 + Cl –> CH3Cl + HCl

Describe what is happening

Answer 7

This is a chain reaction

Methane reacts with chlorine in UV light to make chloromethane and hydrogen chloride gas ⛽️

Question 8

Describe initiation

Cl2 –> Cl• + Cl•
UV light

• is a free radical

Answer 8

~ UV light splits up the chlorine molecules back into atoms

• when the bond breaks each atom takes an electron from the bond
• the chlorine atoms formed an unpaired electron and are called free radicals

Question 9

Describe the step of propagation

CH4 + Cl• –> •CH3 + HCl

Then:

•CH3 + Cl2 –> CH3Cl + Cl•

Answer 9

• The Cl• radical is regenerated and carries on reacting
• This is what is meant by a chain reaction

Chlorine free radicals are very reactive

Question 10

Describe the step for termination

Cl• + Cl• –> Cl2

• CH3 + Cl• –> CH3Cl
• CH3 + •CH3 –> C2H6 ethane

Answer 10

The reaction eventually stops

Other products can be made if the CH3Cl reacts again with a Cl• free radical

The result will be a mixture of CH3Cl CH2Cl2 CHCl3. CCl4. And various products of termination reaction