Haloalkanes

Question 1

What is the process to turn a alkane into a halo alkane and what are the conditions ?

Answer 1

Free-radical substitution
Cl2/Br2 UV light

Question 2

What is the process to turn a halo alkane into a alkene and what are the conditions ?

Answer 2

Elimination
Ethanolic solvent NaOH/KOH

Question 3

What is the process to turn a haloalkane into nitrile and what are the conditions ?

Answer 3

Nucleophilic substitution
aqueous ethanol KCN

Question 4

What is the process to turn a haloalkane into amine and what are the conditions ?

Answer 4

Nucleophilic substitution
Excess ammonia

Question 5

What is the process to turn a haloalkane into a alcohol and what are the conditions ?

Answer 5

Nucleophilic substitution
Warm and aqueous NaOH/KOH

Question 6

What is the process to turn a alcohol into a alkene and what are the conditions ?

Answer 6

Elimination
Hot concentrated H2SO4

Question 7

What is the definition of free-radical ?

Answer 7

Chemical species with a single unpaired electron.

Question 8

State the initiation step for free-radical substitution of Cl2 and describe it.
( use * to represent radical)

Answer 8

Cl2 => 2Cl*

UV light breaks Cl bond by homolytic fission to form Cl radical

Question 9

State the propagation steps for Free-radical substitution of CH4 with Cl2 and describe it.

Answer 9

CH4 + Cl* => *CH3 + HCl

Chlorine radical takes H atom from methane and produces a alkyl radical (*CH3)

CH3 + Cl2 => CH3Cl + Cl

Alkyl radical takes Cl atom from chlorine molecule to form desired product and another Cl*

Question 10

State the main termination step of Free-radical substitution and describe it.

Answer 10

Cl* + *CH3 => CH3Cl

Radicals react together until they get used up making the mechanism stop.

Question 11

What is the purpose of the ozone layer ?

Answer 11

O3 molecules absorb harmful UV rays from sun.

Question 12

What are CFC’s and what do they do ?

Answer 12

Chlorofluorocarbons release Chlorine radicals which react with ozone to break it down.

Question 13

State the initiation step of ozone breakdown mechanism with CFCl3.

Answer 13

CFCl3 => CFCl2 + Cl

Question 14

State the propagation steps for ozone breakdown mechanism with CFCl3.

Answer 14

O3 + Cl* => O2 + ClO
ClO + O3 => 2O2 + Cl*

Question 15

What is the overall equation of the propagation of the ozone breakdown mechanism ?

Answer 15

2O3 => 3O2

Question 16

Explain why CFC’s are so damaging to the ozone layer and how it can be caused by one single chlorine free-radical

Answer 16

1 Chlorine radical speeds up the decomposition of ozone. Its also not used up as it is a chain reaction and more are produced, therefore it is a catalyst to the breaking down of the ozone.

Question 17

What is the definition of a nucleophile ?

Answer 17

A chemical species that can donate a pair of electrons.