Reactions of organic molecules and Pollution

Question 1

What is a free radical

Answer 1

A species with an unpaired electron

Question 2

What are the stages of free radical substitution reactions

Answer 2

Initiation
Propagation
Termination

Question 3

What is Homolyctic Fission

Answer 3

The breaking of a covalent bond with 1 of the bonded electrons going to each atom

Question 4

What is heterolyctic fission

Answer 4

The breaking of a covalent bond with both of the bonded electrons going to one atom. This forms a cation and an anion

Question 5

What happens in the initiation stage

Answer 5

Homolyctic fission of a halogen molecule to form radicals
Cl2 —>Uv light -> Cl• + Cl•

Question 6

What happens in the Propagation stage

Answer 6

Radicals attack the alkane, 2 stages and very rapid chain reaction until no reactants remain

CH4 + Cl• -> CH3 + HCl
CH3• + Cl2 -> CH3Cl + Cl•

Question 7

What happens in the Termination Stage

Answer 7

2 Radicals combine

Cl• + Cl• -> Cl2
CH3• + CH3• -> C2H6
CH3• + Cl• -> CH3Cl

Question 8

Why have CFC ( Chloroflurocarbons) been banned since 1996 in Uk

Answer 8

C-Cl bond broken by UV light
Chlorine free radicals catalyse ozone (O3) destruction

Cl• + O3 -> ClO• + O2
ClO• + O3 -> Cl• + 2O2