Chloroalkanes and CFC's

Question 1

what is a free radical and how is it formed

Answer 1

A free radical is an unpaired electron.

and is formed when a covalent bond splits equally giving one electron to each atom

Question 2

what is the purpose of a free radical substitutin reaction

Answer 2

to replace the “H” with “Br” or “Cl”

Question 3

what are the three steps of a free radical reaction

Answer 3

1) initiation
2) propagation
3) termination

Question 4

INitiation (example, chlorine and methane reacting to form chloromethane)

Answer 4

free radicals r produced
1) sunlight energy breaks Cl-Cl bond - photodissociation
Cl2-> 2Cl*

Question 5

Propagation

Answer 5

free radicals are used up and are created in a chain reaction
1) Cl* attacks methane: Cl* + CH4-> CH3* + HCl
2) new methyl radical can attack another chlorine:
CH3+Cl2-> Ch3Cl + Cl
3) then the Cl* can then attack another CH4 and so on and so forth until all molecules are used up

Question 6

Temination

Answer 6

two free radicals join together to form a STABLE molecule
EG
Cl* + CH3-> Ch3Cl
CH3+Ch3*->C2H6

Question 7

chloroflourocarbons (CFC’s)

Answer 7

contain NOOO hydrogen

Question 8

how does ozone protect us

and why is UV light harmful

Answer 8

ozone acts as a chemical sunscreen and absorbs a lot of UV radiation from the Sun
UV is harmful because it can cause sunburn or even skin cancer

Question 9

how ozone is formed ( free radical substitution)

Answer 9

O2-> O+O

O2+O*->O3

Question 10

OZONE Cl reaction

and what is the overall

Answer 10

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

2O3->3O2

Question 11

key steps to remember in propagation

Answer 11

alkane loses a hydrogen after reactong with three radical
then you get HX where X is the halogen
then the alkane that has 1 less halogen, reacts with a diatomic halogen (in this case chlorine)
forming alkaneHalogen + halogen free radical